Merge from rustc

Cargo.lock

@@ -4673,6 +4673,7 @@ dependencies = [
  "bincode",
  "rustc-hash 2.1.1",
  "serde",
+ "serde_derive",
  "serde_json",
 ]
 

Cargo.toml

@@ -4,7 +4,6 @@ members = [
 # tidy-alphabetical-start
   "compiler/rustc",
   "src/build_helper",
-  "src/etc/test-float-parse",
   "src/rustc-std-workspace/rustc-std-workspace-alloc",
   "src/rustc-std-workspace/rustc-std-workspace-core",
   "src/rustc-std-workspace/rustc-std-workspace-std",
@@ -41,6 +40,7 @@ members = [
   "src/tools/rustdoc-themes",
   "src/tools/rustfmt",
   "src/tools/suggest-tests",
+  "src/tools/test-float-parse",
   "src/tools/tidy",
   "src/tools/tier-check",
   "src/tools/unicode-table-generator",

compiler/rustc_abi/src/canon_abi.rs

@@ -0,0 +1,129 @@
+use std::fmt;
+
+#[cfg(feature = "nightly")]
+use rustc_macros::HashStable_Generic;
+
+use crate::ExternAbi;
+
+/// Calling convention to determine codegen
+///
+/// CanonAbi erases certain distinctions ExternAbi preserves, but remains target-dependent.
+/// There are still both target-specific variants and aliasing variants, though much fewer.
+/// The reason for this step is the frontend may wish to show an ExternAbi but implement that ABI
+/// using a different ABI than the string per se, or describe irrelevant differences, e.g.
+/// - extern "system"
+/// - extern "cdecl"
+/// - extern "C-unwind"
+/// In that sense, this erases mere syntactic distinctions to create a canonical *directive*,
+/// rather than picking the "actual" ABI.
+#[derive(Copy, Clone, Debug)]
+#[derive(PartialOrd, Ord, PartialEq, Eq, Hash)]
+#[cfg_attr(feature = "nightly", derive(HashStable_Generic))]
+pub enum CanonAbi {
+    // NOTE: the use of nested variants for some ABIs is for many targets they don't matter,
+    // and this pushes the complexity of their reasoning to target-specific code,
+    // allowing a `match` to easily exhaustively ignore these subcategories of variants.
+    // Otherwise it is very tempting to avoid matching exhaustively!
+    C,
+    Rust,
+    RustCold,
+
+    /// ABIs relevant to 32-bit Arm targets
+    Arm(ArmCall),
+    /// ABI relevant to GPUs: the entry point for a GPU kernel
+    GpuKernel,
+
+    /// ABIs relevant to bare-metal interrupt targets
+    // FIXME(workingjubilee): a particular reason for this nesting is we might not need these?
+    // interrupt ABIs should have the same properties:
+    // - uncallable by Rust calls, as LLVM rejects it in most cases
+    // - uses a preserve-all-registers *callee* convention
+    // - should always return `-> !` (effectively... it can't use normal `ret`)
+    // what differs between targets is
+    // - allowed arguments: x86 differs slightly, having 2-3 arguments which are handled magically
+    // - may need special prologues/epilogues for some interrupts, without affecting "call ABI"
+    Interrupt(InterruptKind),
+
+    /// ABIs relevant to Windows or x86 targets
+    X86(X86Call),
+}
+
+impl fmt::Display for CanonAbi {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        // convert to the ExternAbi that *shares a string* with this CanonAbi.
+        // FIXME: ideally we'd avoid printing `CanonAbi`, and preserve `ExternAbi` everywhere
+        // that we need to generate error messages.
+        let erased_abi = match self {
+            CanonAbi::C => ExternAbi::C { unwind: false },
+            CanonAbi::Rust => ExternAbi::Rust,
+            CanonAbi::RustCold => ExternAbi::RustCold,
+            CanonAbi::Arm(arm_call) => match arm_call {
+                ArmCall::Aapcs => ExternAbi::Aapcs { unwind: false },
+                ArmCall::CCmseNonSecureCall => ExternAbi::CCmseNonSecureCall,
+                ArmCall::CCmseNonSecureEntry => ExternAbi::CCmseNonSecureEntry,
+            },
+            CanonAbi::GpuKernel => ExternAbi::GpuKernel,
+            CanonAbi::Interrupt(interrupt_kind) => match interrupt_kind {
+                InterruptKind::Avr => ExternAbi::AvrInterrupt,
+                InterruptKind::AvrNonBlocking => ExternAbi::AvrNonBlockingInterrupt,
+                InterruptKind::Msp430 => ExternAbi::Msp430Interrupt,
+                InterruptKind::RiscvMachine => ExternAbi::RiscvInterruptM,
+                InterruptKind::RiscvSupervisor => ExternAbi::RiscvInterruptS,
+                InterruptKind::X86 => ExternAbi::X86Interrupt,
+            },
+            CanonAbi::X86(x86_call) => match x86_call {
+                X86Call::Fastcall => ExternAbi::Fastcall { unwind: false },
+                X86Call::Stdcall => ExternAbi::Stdcall { unwind: false },
+                X86Call::SysV64 => ExternAbi::SysV64 { unwind: false },
+                X86Call::Thiscall => ExternAbi::Thiscall { unwind: false },
+                X86Call::Vectorcall => ExternAbi::Vectorcall { unwind: false },
+                X86Call::Win64 => ExternAbi::Win64 { unwind: false },
+            },
+        };
+        erased_abi.as_str().fmt(f)
+    }
+}
+
+/// Callee codegen for interrupts
+///
+/// This is named differently from the "Call" enums because it is different:
+/// these "ABI" differences are not relevant to callers, since there is "no caller".
+/// These only affect callee codegen. making their categorization as distinct ABIs a bit peculiar.
+#[derive(Copy, Clone, Debug)]
+#[derive(PartialOrd, Ord, PartialEq, Eq, Hash)]
+#[cfg_attr(feature = "nightly", derive(HashStable_Generic))]
+pub enum InterruptKind {
+    Avr,
+    AvrNonBlocking,
+    Msp430,
+    RiscvMachine,
+    RiscvSupervisor,
+    X86,
+}
+
+/// ABIs defined for x86-{32,64}
+///
+/// One of SysV64 or Win64 may alias the C ABI, and arguably Win64 is cross-platform now?
+#[derive(Clone, Copy, Debug)]
+#[derive(PartialOrd, Ord, PartialEq, Eq, Hash)]
+#[cfg_attr(feature = "nightly", derive(HashStable_Generic))]
+pub enum X86Call {
+    /// "fastcall" has both GNU and Windows variants
+    Fastcall,
+    /// "stdcall" has both GNU and Windows variants
+    Stdcall,
+    SysV64,
+    Thiscall,
+    Vectorcall,
+    Win64,
+}
+
+/// ABIs defined for 32-bit Arm
+#[derive(Copy, Clone, Debug)]
+#[derive(PartialOrd, Ord, PartialEq, Eq, Hash)]
+#[cfg_attr(feature = "nightly", derive(HashStable_Generic))]
+pub enum ArmCall {
+    Aapcs,
+    CCmseNonSecureCall,
+    CCmseNonSecureEntry,
+}

compiler/rustc_abi/src/extern_abi.rs

@@ -7,69 +7,98 @@ use rustc_data_structures::stable_hasher::{HashStable, StableHasher, StableOrd};
 #[cfg(feature = "nightly")]
 use rustc_macros::{Decodable, Encodable};
 
+use crate::AbiFromStrErr;
+
 #[cfg(test)]
 mod tests;
 
-use ExternAbi as Abi;
-
+/// ABI we expect to see within `extern "{abi}"`
 #[derive(Clone, Copy, Debug)]
 #[cfg_attr(feature = "nightly", derive(Encodable, Decodable))]
 pub enum ExternAbi {
-    // Some of the ABIs come first because every time we add a new ABI, we have to re-bless all the
-    // hashing tests. These are used in many places, so giving them stable values reduces test
-    // churn. The specific values are meaningless.
-    Rust,
+    /* universal */
+    /// presumed C ABI for the platform
     C {
         unwind: bool,
     },
+    /// ABI of the "system" interface, e.g. the Win32 API, always "aliasing"
+    System {
+        unwind: bool,
+    },
+
+    /// that's us!
+    Rust,
+    /// the mostly-unused `unboxed_closures` ABI, effectively now an impl detail unless someone
+    /// puts in the work to make it viable again... but would we need a special ABI?
+    RustCall,
+    /// For things unlikely to be called, where reducing register pressure in
+    /// `extern "Rust"` callers is worth paying extra cost in the callee.
+    /// Stronger than just `#[cold]` because `fn` pointers might be incompatible.
+    RustCold,
+
+    /// Unstable impl detail that directly uses Rust types to describe the ABI to LLVM.
+    /// Even normally-compatible Rust types can become ABI-incompatible with this ABI!
+    Unadjusted,
+
+    /// UEFI ABI, usually an alias of C, but sometimes an arch-specific alias
+    /// and only valid on platforms that have a UEFI standard
+    EfiApi,
+
+    /* arm */
+    /// Arm Architecture Procedure Call Standard, sometimes `ExternAbi::C` is an alias for this
+    Aapcs {
+        unwind: bool,
+    },
+    /// extremely constrained barely-C ABI for TrustZone
+    CCmseNonSecureCall,
+    /// extremely constrained barely-C ABI for TrustZone
+    CCmseNonSecureEntry,
+
+    /* gpu */
+    /// An entry-point function called by the GPU's host
+    // FIXME: should not be callable from Rust on GPU targets, is for host's use only
+    GpuKernel,
+    /// An entry-point function called by the GPU's host
+    // FIXME: why do we have two of these?
+    PtxKernel,
+
+    /* interrupt */
+    AvrInterrupt,
+    AvrNonBlockingInterrupt,
+    Msp430Interrupt,
+    RiscvInterruptM,
+    RiscvInterruptS,
+    X86Interrupt,
+
+    /* x86 */
+    /// `ExternAbi::C` but spelled funny because x86
     Cdecl {
         unwind: bool,
     },
+    /// gnu-stdcall on "unix" and win-stdcall on "windows"
     Stdcall {
         unwind: bool,
     },
+    /// gnu-fastcall on "unix" and win-fastcall on "windows"
     Fastcall {
         unwind: bool,
     },
-    Vectorcall {
-        unwind: bool,
-    },
+    /// windows C++ ABI
     Thiscall {
         unwind: bool,
     },
-    Aapcs {
+    /// uses AVX and stuff
+    Vectorcall {
+        unwind: bool,
+    },
+
+    /* x86_64 */
+    SysV64 {
         unwind: bool,
     },
     Win64 {
         unwind: bool,
     },
-    SysV64 {
-        unwind: bool,
-    },
-    PtxKernel,
-    Msp430Interrupt,
-    X86Interrupt,
-    /// An entry-point function called by the GPU's host
-    // FIXME: should not be callable from Rust on GPU targets, is for host's use only
-    GpuKernel,
-    EfiApi,
-    AvrInterrupt,
-    AvrNonBlockingInterrupt,
-    CCmseNonSecureCall,
-    CCmseNonSecureEntry,
-    System {
-        unwind: bool,
-    },
-    RustCall,
-    /// *Not* a stable ABI, just directly use the Rust types to describe the ABI for LLVM. Even
-    /// normally ABI-compatible Rust types can become ABI-incompatible with this ABI!
-    Unadjusted,
-    /// For things unlikely to be called, where reducing register pressure in
-    /// `extern "Rust"` callers is worth paying extra cost in the callee.
-    /// Stronger than just `#[cold]` because `fn` pointers might be incompatible.
-    RustCold,
-    RiscvInterruptM,
-    RiscvInterruptS,
 }
 
 macro_rules! abi_impls {
@@ -99,11 +128,6 @@ macro_rules! abi_impls {
     }
 }
 
-#[derive(Debug)]
-pub enum AbiFromStrErr {
-    Unknown,
-}
-
 abi_impls! {
     ExternAbi = {
             C { unwind: false } =><= "C",
@@ -227,7 +251,7 @@ pub fn all_names() -> Vec<&'static str> {
 
 impl ExternAbi {
     /// Default ABI chosen for `extern fn` declarations without an explicit ABI.
-    pub const FALLBACK: Abi = Abi::C { unwind: false };
+    pub const FALLBACK: ExternAbi = ExternAbi::C { unwind: false };
 
     pub fn name(self) -> &'static str {
         self.as_str()

compiler/rustc_abi/src/layout.rs

@@ -758,7 +758,7 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
                         niche_variants,
                         niche_start,
                     },
-                    tag_field: 0,
+                    tag_field: FieldIdx::new(0),
                     variants: IndexVec::new(),
                 },
                 fields: FieldsShape::Arbitrary {
@@ -1072,7 +1072,7 @@ impl<Cx: HasDataLayout> LayoutCalculator<Cx> {
             variants: Variants::Multiple {
                 tag,
                 tag_encoding: TagEncoding::Direct,
-                tag_field: 0,
+                tag_field: FieldIdx::new(0),
                 variants: IndexVec::new(),
             },
             fields: FieldsShape::Arbitrary {

compiler/rustc_abi/src/layout/coroutine.rs

@@ -158,7 +158,7 @@ pub(super) fn layout<
     // Build a prefix layout, including "promoting" all ineligible
     // locals as part of the prefix. We compute the layout of all of
     // these fields at once to get optimal packing.
-    let tag_index = prefix_layouts.len();
+    let tag_index = prefix_layouts.next_index();
 
     // `variant_fields` already accounts for the reserved variants, so no need to add them.
     let max_discr = (variant_fields.len() - 1) as u128;
@@ -187,7 +187,7 @@ pub(super) fn layout<
 
             // "a" (`0..b_start`) and "b" (`b_start..`) correspond to
             // "outer" and "promoted" fields respectively.
-            let b_start = FieldIdx::new(tag_index + 1);
+            let b_start = tag_index.plus(1);
             let offsets_b = IndexVec::from_raw(offsets.raw.split_off(b_start.index()));
             let offsets_a = offsets;
 

compiler/rustc_abi/src/layout/ty.rs

@@ -39,6 +39,13 @@ rustc_index::newtype_index! {
     pub struct FieldIdx {}
 }
 
+impl FieldIdx {
+    /// The second field, at index 1.
+    ///
+    /// For use alongside [`FieldIdx::ZERO`], particularly with scalar pairs.
+    pub const ONE: FieldIdx = FieldIdx::from_u32(1);
+}
+
 rustc_index::newtype_index! {
     /// The *source-order* index of a variant in a type.
     ///
@@ -274,7 +281,7 @@ impl<'a, Ty> TyAndLayout<'a, Ty> {
 
     /// Finds the one field that is not a 1-ZST.
     /// Returns `None` if there are multiple non-1-ZST fields or only 1-ZST-fields.
-    pub fn non_1zst_field<C>(&self, cx: &C) -> Option<(usize, Self)>
+    pub fn non_1zst_field<C>(&self, cx: &C) -> Option<(FieldIdx, Self)>
     where
         Ty: TyAbiInterface<'a, C> + Copy,
     {
@@ -288,7 +295,7 @@ impl<'a, Ty> TyAndLayout<'a, Ty> {
                 // More than one non-1-ZST field.
                 return None;
             }
-            found = Some((field_idx, field));
+            found = Some((FieldIdx::from_usize(field_idx), field));
         }
         found
     }

compiler/rustc_abi/src/lib.rs

@@ -55,13 +55,14 @@ use rustc_index::{Idx, IndexSlice, IndexVec};
 use rustc_macros::{Decodable_NoContext, Encodable_NoContext, HashStable_Generic};
 
 mod callconv;
+mod canon_abi;
+mod extern_abi;
 mod layout;
 #[cfg(test)]
 mod tests;
 
-mod extern_abi;
-
 pub use callconv::{Heterogeneous, HomogeneousAggregate, Reg, RegKind};
+pub use canon_abi::{ArmCall, CanonAbi, InterruptKind, X86Call};
 pub use extern_abi::{ExternAbi, all_names};
 #[cfg(feature = "nightly")]
 pub use layout::{FIRST_VARIANT, FieldIdx, Layout, TyAbiInterface, TyAndLayout, VariantIdx};
@@ -1572,7 +1573,7 @@ pub enum Variants<FieldIdx: Idx, VariantIdx: Idx> {
     Multiple {
         tag: Scalar,
         tag_encoding: TagEncoding<VariantIdx>,
-        tag_field: usize,
+        tag_field: FieldIdx,
         variants: IndexVec<VariantIdx, LayoutData<FieldIdx, VariantIdx>>,
     },
 }
@@ -1895,3 +1896,11 @@ pub enum StructKind {
     /// A univariant, but with a prefix of an arbitrary size & alignment (e.g., enum tag).
     Prefixed(Size, Align),
 }
+
+#[derive(Clone, Debug)]
+pub enum AbiFromStrErr {
+    /// not a known ABI
+    Unknown,
+    /// no "-unwind" variant can be used here
+    NoExplicitUnwind,
+}

compiler/rustc_ast/src/ast.rs

@@ -99,8 +99,15 @@ pub struct Path {
 
 impl PartialEq<Symbol> for Path {
     #[inline]
-    fn eq(&self, symbol: &Symbol) -> bool {
-        matches!(&self.segments[..], [segment] if segment.ident.name == *symbol)
+    fn eq(&self, name: &Symbol) -> bool {
+        if let [segment] = self.segments.as_ref()
+            && segment.args.is_none()
+            && segment.ident.name == *name
+        {
+            true
+        } else {
+            false
+        }
     }
 }
 
@@ -120,17 +127,6 @@ impl Path {
         Path { segments: thin_vec![PathSegment::from_ident(ident)], span: ident.span, tokens: None }
     }
 
-    pub fn is_ident(&self, name: Symbol) -> bool {
-        if let [segment] = self.segments.as_ref()
-            && segment.args.is_none()
-            && segment.ident.name == name
-        {
-            true
-        } else {
-            false
-        }
-    }
-
     pub fn is_global(&self) -> bool {
         self.segments.first().is_some_and(|segment| segment.ident.name == kw::PathRoot)
     }
@@ -1123,10 +1119,9 @@ impl Stmt {
     pub fn add_trailing_semicolon(mut self) -> Self {
         self.kind = match self.kind {
             StmtKind::Expr(expr) => StmtKind::Semi(expr),
-            StmtKind::MacCall(mac) => {
-                StmtKind::MacCall(mac.map(|MacCallStmt { mac, style: _, attrs, tokens }| {
-                    MacCallStmt { mac, style: MacStmtStyle::Semicolon, attrs, tokens }
-                }))
+            StmtKind::MacCall(mut mac) => {
+                mac.style = MacStmtStyle::Semicolon;
+                StmtKind::MacCall(mac)
             }
             kind => kind,
         };
@@ -1728,7 +1723,7 @@ pub enum ExprKind {
     ///
     /// Usually not written directly in user code but
     /// indirectly via the macro `core::mem::offset_of!(...)`.
-    OffsetOf(P<Ty>, P<[Ident]>),
+    OffsetOf(P<Ty>, Vec<Ident>),
 
     /// A macro invocation; pre-expansion.
     MacCall(P<MacCall>),
@@ -2465,6 +2460,39 @@ impl TyKind {
             None
         }
     }
+
+    /// Returns `true` if this type is considered a scalar primitive (e.g.,
+    /// `i32`, `u8`, `bool`, etc).
+    ///
+    /// This check is based on **symbol equality** and does **not** remove any
+    /// path prefixes or references. If a type alias or shadowing is present
+    /// (e.g., `type i32 = CustomType;`), this method will still return `true`
+    /// for `i32`, even though it may not refer to the primitive type.
+    pub fn maybe_scalar(&self) -> bool {
+        let Some(ty_sym) = self.is_simple_path() else {
+            // unit type
+            return self.is_unit();
+        };
+        matches!(
+            ty_sym,
+            sym::i8
+                | sym::i16
+                | sym::i32
+                | sym::i64
+                | sym::i128
+                | sym::u8
+                | sym::u16
+                | sym::u32
+                | sym::u64
+                | sym::u128
+                | sym::f16
+                | sym::f32
+                | sym::f64
+                | sym::f128
+                | sym::char
+                | sym::bool
+        )
+    }
 }
 
 /// A pattern type pattern.

compiler/rustc_ast/src/attr/mod.rs

@@ -63,7 +63,7 @@ impl Attribute {
 
     pub fn unwrap_normal_item(self) -> AttrItem {
         match self.kind {
-            AttrKind::Normal(normal) => normal.into_inner().item,
+            AttrKind::Normal(normal) => normal.item,
             AttrKind::DocComment(..) => panic!("unexpected doc comment"),
         }
     }

compiler/rustc_ast/src/mut_visit.rs

@@ -12,7 +12,6 @@ use std::panic;
 
 use rustc_data_structures::flat_map_in_place::FlatMapInPlace;
 use rustc_data_structures::stack::ensure_sufficient_stack;
-use rustc_span::source_map::Spanned;
 use rustc_span::{Ident, Span};
 use smallvec::{Array, SmallVec, smallvec};
 use thin_vec::ThinVec;
@@ -209,11 +208,7 @@ pub trait MutVisitor: Sized {
     }
 
     fn visit_ident(&mut self, i: &mut Ident) {
-        walk_ident(self, i);
-    }
-
-    fn visit_modifiers(&mut self, m: &mut TraitBoundModifiers) {
-        walk_modifiers(self, m);
+        self.visit_span(&mut i.span);
     }
 
     fn visit_path(&mut self, p: &mut Path) {
@@ -368,6 +363,33 @@ pub trait MutVisitor: Sized {
 
 super::common_visitor_and_walkers!((mut) MutVisitor);
 
+macro_rules! generate_flat_map_visitor_fns {
+    ($($name:ident, $Ty:ty, $flat_map_fn:ident$(, $param:ident: $ParamTy:ty)*;)+) => {
+        $(
+            fn $name<V: MutVisitor>(
+                vis: &mut V,
+                values: &mut ThinVec<$Ty>,
+                $(
+                    $param: $ParamTy,
+                )*
+            ) {
+                values.flat_map_in_place(|value| vis.$flat_map_fn(value$(,$param)*));
+            }
+        )+
+    }
+}
+
+generate_flat_map_visitor_fns! {
+    visit_items, P<Item>, flat_map_item;
+    visit_foreign_items, P<ForeignItem>, flat_map_foreign_item;
+    visit_generic_params, GenericParam, flat_map_generic_param;
+    visit_stmts, Stmt, flat_map_stmt;
+    visit_exprs, P<Expr>, filter_map_expr;
+    visit_pat_fields, PatField, flat_map_pat_field;
+    visit_variants, Variant, flat_map_variant;
+    visit_assoc_items, P<AssocItem>, flat_map_assoc_item, ctxt: AssocCtxt;
+}
+
 #[inline]
 fn visit_vec<T, F>(elems: &mut Vec<T>, mut visit_elem: F)
 where
@@ -404,15 +426,6 @@ fn visit_attrs<T: MutVisitor>(vis: &mut T, attrs: &mut AttrVec) {
     }
 }
 
-#[allow(unused)]
-fn visit_exprs<T: MutVisitor>(vis: &mut T, exprs: &mut Vec<P<Expr>>) {
-    exprs.flat_map_in_place(|expr| vis.filter_map_expr(expr))
-}
-
-fn visit_thin_exprs<T: MutVisitor>(vis: &mut T, exprs: &mut ThinVec<P<Expr>>) {
-    exprs.flat_map_in_place(|expr| vis.filter_map_expr(expr))
-}
-
 fn visit_attr_args<T: MutVisitor>(vis: &mut T, args: &mut AttrArgs) {
     match args {
         AttrArgs::Empty => {}
@@ -431,15 +444,6 @@ fn visit_delim_args<T: MutVisitor>(vis: &mut T, args: &mut DelimArgs) {
     vis.visit_span(close);
 }
 
-pub fn walk_pat_field<T: MutVisitor>(vis: &mut T, fp: &mut PatField) {
-    let PatField { attrs, id, ident, is_placeholder: _, is_shorthand: _, pat, span } = fp;
-    vis.visit_id(id);
-    visit_attrs(vis, attrs);
-    vis.visit_ident(ident);
-    vis.visit_pat(pat);
-    vis.visit_span(span);
-}
-
 pub fn walk_flat_map_pat_field<T: MutVisitor>(
     vis: &mut T,
     mut fp: PatField,
@@ -448,21 +452,13 @@ pub fn walk_flat_map_pat_field<T: MutVisitor>(
     smallvec![fp]
 }
 
-fn walk_use_tree<T: MutVisitor>(vis: &mut T, use_tree: &mut UseTree) {
-    let UseTree { prefix, kind, span } = use_tree;
-    vis.visit_path(prefix);
-    match kind {
-        UseTreeKind::Simple(rename) => visit_opt(rename, |rename| vis.visit_ident(rename)),
-        UseTreeKind::Nested { items, span } => {
-            for (tree, id) in items {
-                vis.visit_id(id);
-                vis.visit_use_tree(tree);
-            }
-            vis.visit_span(span);
-        }
-        UseTreeKind::Glob => {}
-    }
-    vis.visit_span(span);
+fn visit_nested_use_tree<V: MutVisitor>(
+    vis: &mut V,
+    nested_tree: &mut UseTree,
+    nested_id: &mut NodeId,
+) {
+    vis.visit_id(nested_id);
+    vis.visit_use_tree(nested_tree);
 }
 
 pub fn walk_arm<T: MutVisitor>(vis: &mut T, arm: &mut Arm) {
@@ -499,83 +495,6 @@ fn walk_assoc_item_constraint<T: MutVisitor>(
     vis.visit_span(span);
 }
 
-pub fn walk_ty<T: MutVisitor>(vis: &mut T, ty: &mut Ty) {
-    let Ty { id, kind, span, tokens: _ } = ty;
-    vis.visit_id(id);
-    match kind {
-        TyKind::Err(_guar) => {}
-        TyKind::Infer | TyKind::ImplicitSelf | TyKind::Dummy | TyKind::Never | TyKind::CVarArgs => {
-        }
-        TyKind::Slice(ty) => vis.visit_ty(ty),
-        TyKind::Ptr(MutTy { ty, mutbl: _ }) => vis.visit_ty(ty),
-        TyKind::Ref(lt, MutTy { ty, mutbl: _ }) | TyKind::PinnedRef(lt, MutTy { ty, mutbl: _ }) => {
-            visit_opt(lt, |lt| vis.visit_lifetime(lt));
-            vis.visit_ty(ty);
-        }
-        TyKind::BareFn(bft) => {
-            let BareFnTy { safety, ext: _, generic_params, decl, decl_span } = bft.deref_mut();
-            visit_safety(vis, safety);
-            generic_params.flat_map_in_place(|param| vis.flat_map_generic_param(param));
-            vis.visit_fn_decl(decl);
-            vis.visit_span(decl_span);
-        }
-        TyKind::UnsafeBinder(binder) => {
-            let UnsafeBinderTy { generic_params, inner_ty } = binder.deref_mut();
-            generic_params.flat_map_in_place(|param| vis.flat_map_generic_param(param));
-            vis.visit_ty(inner_ty);
-        }
-        TyKind::Tup(tys) => visit_thin_vec(tys, |ty| vis.visit_ty(ty)),
-        TyKind::Paren(ty) => vis.visit_ty(ty),
-        TyKind::Pat(ty, pat) => {
-            vis.visit_ty(ty);
-            vis.visit_ty_pat(pat);
-        }
-        TyKind::Path(qself, path) => {
-            vis.visit_qself(qself);
-            vis.visit_path(path);
-        }
-        TyKind::Array(ty, length) => {
-            vis.visit_ty(ty);
-            vis.visit_anon_const(length);
-        }
-        TyKind::Typeof(expr) => vis.visit_anon_const(expr),
-        TyKind::TraitObject(bounds, _syntax) => {
-            visit_vec(bounds, |bound| vis.visit_param_bound(bound, BoundKind::TraitObject))
-        }
-        TyKind::ImplTrait(id, bounds) => {
-            vis.visit_id(id);
-            visit_vec(bounds, |bound| vis.visit_param_bound(bound, BoundKind::Impl));
-        }
-        TyKind::MacCall(mac) => vis.visit_mac_call(mac),
-    }
-    vis.visit_span(span);
-}
-
-pub fn walk_ty_pat<T: MutVisitor>(vis: &mut T, ty: &mut TyPat) {
-    let TyPat { id, kind, span, tokens: _ } = ty;
-    vis.visit_id(id);
-    match kind {
-        TyPatKind::Range(start, end, _include_end) => {
-            visit_opt(start, |c| vis.visit_anon_const(c));
-            visit_opt(end, |c| vis.visit_anon_const(c));
-        }
-        TyPatKind::Or(variants) => visit_thin_vec(variants, |p| vis.visit_ty_pat(p)),
-        TyPatKind::Err(_) => {}
-    }
-    vis.visit_span(span);
-}
-
-pub fn walk_variant<T: MutVisitor>(visitor: &mut T, variant: &mut Variant) {
-    let Variant { ident, vis, attrs, id, data, disr_expr, span, is_placeholder: _ } = variant;
-    visitor.visit_id(id);
-    visit_attrs(visitor, attrs);
-    visitor.visit_vis(vis);
-    visitor.visit_ident(ident);
-    visitor.visit_variant_data(data);
-    visit_opt(disr_expr, |disr_expr| visitor.visit_anon_const(disr_expr));
-    visitor.visit_span(span);
-}
-
 pub fn walk_flat_map_variant<T: MutVisitor>(
     vis: &mut T,
     mut variant: Variant,
@@ -584,32 +503,6 @@ pub fn walk_flat_map_variant<T: MutVisitor>(
     smallvec![variant]
 }
 
-fn walk_ident<T: MutVisitor>(vis: &mut T, Ident { name: _, span }: &mut Ident) {
-    vis.visit_span(span);
-}
-
-fn walk_path_segment<T: MutVisitor>(vis: &mut T, segment: &mut PathSegment) {
-    let PathSegment { ident, id, args } = segment;
-    vis.visit_id(id);
-    vis.visit_ident(ident);
-    visit_opt(args, |args| vis.visit_generic_args(args));
-}
-
-fn walk_path<T: MutVisitor>(vis: &mut T, Path { segments, span, tokens: _ }: &mut Path) {
-    for segment in segments {
-        vis.visit_path_segment(segment);
-    }
-    vis.visit_span(span);
-}
-
-fn walk_qself<T: MutVisitor>(vis: &mut T, qself: &mut Option<P<QSelf>>) {
-    visit_opt(qself, |qself| {
-        let QSelf { ty, path_span, position: _ } = &mut **qself;
-        vis.visit_ty(ty);
-        vis.visit_span(path_span);
-    })
-}
-
 fn walk_generic_args<T: MutVisitor>(vis: &mut T, generic_args: &mut GenericArgs) {
     match generic_args {
         GenericArgs::AngleBracketed(data) => vis.visit_angle_bracketed_parameter_data(data),
@@ -643,27 +536,6 @@ fn walk_parenthesized_parameter_data<T: MutVisitor>(vis: &mut T, args: &mut Pare
     vis.visit_span(inputs_span);
 }
 
-fn walk_local<T: MutVisitor>(vis: &mut T, local: &mut Local) {
-    let Local { id, super_, pat, ty, kind, span, colon_sp, attrs, tokens: _ } = local;
-    visit_opt(super_, |sp| vis.visit_span(sp));
-    vis.visit_id(id);
-    visit_attrs(vis, attrs);
-    vis.visit_pat(pat);
-    visit_opt(ty, |ty| vis.visit_ty(ty));
-    match kind {
-        LocalKind::Decl => {}
-        LocalKind::Init(init) => {
-            vis.visit_expr(init);
-        }
-        LocalKind::InitElse(init, els) => {
-            vis.visit_expr(init);
-            vis.visit_block(els);
-        }
-    }
-    visit_opt(colon_sp, |sp| vis.visit_span(sp));
-    vis.visit_span(span);
-}
-
 fn walk_attribute<T: MutVisitor>(vis: &mut T, attr: &mut Attribute) {
     let Attribute { kind, id: _, style: _, span } = attr;
     match kind {
@@ -729,18 +601,6 @@ fn walk_closure_binder<T: MutVisitor>(vis: &mut T, binder: &mut ClosureBinder) {
     }
 }
 
-fn walk_coroutine_kind<T: MutVisitor>(vis: &mut T, coroutine_kind: &mut CoroutineKind) {
-    match coroutine_kind {
-        CoroutineKind::Async { span, closure_id, return_impl_trait_id }
-        | CoroutineKind::Gen { span, closure_id, return_impl_trait_id }
-        | CoroutineKind::AsyncGen { span, closure_id, return_impl_trait_id } => {
-            vis.visit_id(closure_id);
-            vis.visit_id(return_impl_trait_id);
-            vis.visit_span(span);
-        }
-    }
-}
-
 fn walk_fn<T: MutVisitor>(vis: &mut T, kind: FnKind<'_>) {
     match kind {
         FnKind::Fn(
@@ -925,35 +785,6 @@ fn walk_variant_data<T: MutVisitor>(vis: &mut T, vdata: &mut VariantData) {
     }
 }
 
-fn walk_trait_ref<T: MutVisitor>(vis: &mut T, TraitRef { path, ref_id }: &mut TraitRef) {
-    vis.visit_id(ref_id);
-    vis.visit_path(path);
-}
-
-fn walk_poly_trait_ref<T: MutVisitor>(vis: &mut T, p: &mut PolyTraitRef) {
-    let PolyTraitRef { bound_generic_params, modifiers, trait_ref, span } = p;
-    vis.visit_modifiers(modifiers);
-    bound_generic_params.flat_map_in_place(|param| vis.flat_map_generic_param(param));
-    vis.visit_trait_ref(trait_ref);
-    vis.visit_span(span);
-}
-
-fn walk_modifiers<V: MutVisitor>(vis: &mut V, m: &mut TraitBoundModifiers) {
-    let TraitBoundModifiers { constness, asyncness, polarity } = m;
-    match constness {
-        BoundConstness::Never => {}
-        BoundConstness::Always(span) | BoundConstness::Maybe(span) => vis.visit_span(span),
-    }
-    match asyncness {
-        BoundAsyncness::Normal => {}
-        BoundAsyncness::Async(span) => vis.visit_span(span),
-    }
-    match polarity {
-        BoundPolarity::Positive => {}
-        BoundPolarity::Negative(span) | BoundPolarity::Maybe(span) => vis.visit_span(span),
-    }
-}
-
 pub fn walk_field_def<T: MutVisitor>(visitor: &mut T, fd: &mut FieldDef) {
     let FieldDef { span, ident, vis, id, ty, attrs, is_placeholder: _, safety, default } = fd;
     visitor.visit_id(id);
@@ -974,15 +805,6 @@ pub fn walk_flat_map_field_def<T: MutVisitor>(
     smallvec![fd]
 }
 
-pub fn walk_expr_field<T: MutVisitor>(vis: &mut T, f: &mut ExprField) {
-    let ExprField { ident, expr, span, is_shorthand: _, attrs, id, is_placeholder: _ } = f;
-    vis.visit_id(id);
-    visit_attrs(vis, attrs);
-    vis.visit_ident(ident);
-    vis.visit_expr(expr);
-    vis.visit_span(span);
-}
-
 pub fn walk_flat_map_expr_field<T: MutVisitor>(
     vis: &mut T,
     mut f: ExprField,
@@ -991,13 +813,6 @@ pub fn walk_flat_map_expr_field<T: MutVisitor>(
     smallvec![f]
 }
 
-pub fn walk_block<T: MutVisitor>(vis: &mut T, block: &mut Block) {
-    let Block { id, stmts, rules: _, span, tokens: _ } = block;
-    vis.visit_id(id);
-    stmts.flat_map_in_place(|stmt| vis.flat_map_stmt(stmt));
-    vis.visit_span(span);
-}
-
 pub fn walk_item_kind<K: WalkItemKind>(
     kind: &mut K,
     span: Span,
@@ -1009,16 +824,6 @@ pub fn walk_item_kind<K: WalkItemKind>(
     kind.walk(span, id, visibility, ctxt, vis)
 }
 
-pub fn walk_crate<T: MutVisitor>(vis: &mut T, krate: &mut Crate) {
-    let Crate { attrs, items, spans, id, is_placeholder: _ } = krate;
-    vis.visit_id(id);
-    visit_attrs(vis, attrs);
-    items.flat_map_in_place(|item| vis.flat_map_item(item));
-    let ModSpans { inner_span, inject_use_span } = spans;
-    vis.visit_span(inner_span);
-    vis.visit_span(inject_use_span);
-}
-
 pub fn walk_flat_map_item(vis: &mut impl MutVisitor, mut item: P<Item>) -> SmallVec<[P<Item>; 1]> {
     vis.visit_item(&mut item);
     smallvec![item]
@@ -1041,57 +846,6 @@ pub fn walk_flat_map_assoc_item(
     smallvec![item]
 }
 
-pub fn walk_pat<T: MutVisitor>(vis: &mut T, pat: &mut Pat) {
-    let Pat { id, kind, span, tokens: _ } = pat;
-    vis.visit_id(id);
-    match kind {
-        PatKind::Err(_guar) => {}
-        PatKind::Missing | PatKind::Wild | PatKind::Rest | PatKind::Never => {}
-        PatKind::Ident(_binding_mode, ident, sub) => {
-            vis.visit_ident(ident);
-            visit_opt(sub, |sub| vis.visit_pat(sub));
-        }
-        PatKind::Expr(e) => vis.visit_expr(e),
-        PatKind::TupleStruct(qself, path, elems) => {
-            vis.visit_qself(qself);
-            vis.visit_path(path);
-            visit_thin_vec(elems, |elem| vis.visit_pat(elem));
-        }
-        PatKind::Path(qself, path) => {
-            vis.visit_qself(qself);
-            vis.visit_path(path);
-        }
-        PatKind::Struct(qself, path, fields, _etc) => {
-            vis.visit_qself(qself);
-            vis.visit_path(path);
-            fields.flat_map_in_place(|field| vis.flat_map_pat_field(field));
-        }
-        PatKind::Box(inner) => vis.visit_pat(inner),
-        PatKind::Deref(inner) => vis.visit_pat(inner),
-        PatKind::Ref(inner, _mutbl) => vis.visit_pat(inner),
-        PatKind::Range(e1, e2, Spanned { span: _, node: _ }) => {
-            visit_opt(e1, |e| vis.visit_expr(e));
-            visit_opt(e2, |e| vis.visit_expr(e));
-            vis.visit_span(span);
-        }
-        PatKind::Guard(p, e) => {
-            vis.visit_pat(p);
-            vis.visit_expr(e);
-        }
-        PatKind::Tuple(elems) | PatKind::Slice(elems) | PatKind::Or(elems) => {
-            visit_thin_vec(elems, |elem| vis.visit_pat(elem))
-        }
-        PatKind::Paren(inner) => vis.visit_pat(inner),
-        PatKind::MacCall(mac) => vis.visit_mac_call(mac),
-    }
-    vis.visit_span(span);
-}
-
-fn walk_anon_const<T: MutVisitor>(vis: &mut T, AnonConst { id, value }: &mut AnonConst) {
-    vis.visit_id(id);
-    vis.visit_expr(value);
-}
-
 fn walk_inline_asm<T: MutVisitor>(vis: &mut T, asm: &mut InlineAsm) {
     // FIXME: Visit spans inside all this currently ignored stuff.
     let InlineAsm {
@@ -1151,7 +905,7 @@ pub fn walk_expr<T: MutVisitor>(vis: &mut T, Expr { kind, id, span, attrs, token
     vis.visit_id(id);
     visit_attrs(vis, attrs);
     match kind {
-        ExprKind::Array(exprs) => visit_thin_exprs(vis, exprs),
+        ExprKind::Array(exprs) => visit_exprs(vis, exprs),
         ExprKind::ConstBlock(anon_const) => {
             vis.visit_anon_const(anon_const);
         }
@@ -1159,10 +913,10 @@ pub fn walk_expr<T: MutVisitor>(vis: &mut T, Expr { kind, id, span, attrs, token
             vis.visit_expr(expr);
             vis.visit_anon_const(count);
         }
-        ExprKind::Tup(exprs) => visit_thin_exprs(vis, exprs),
+        ExprKind::Tup(exprs) => visit_exprs(vis, exprs),
         ExprKind::Call(f, args) => {
             vis.visit_expr(f);
-            visit_thin_exprs(vis, args);
+            visit_exprs(vis, args);
         }
         ExprKind::MethodCall(box MethodCall {
             seg: PathSegment { ident, id, args: seg_args },
@@ -1174,7 +928,7 @@ pub fn walk_expr<T: MutVisitor>(vis: &mut T, Expr { kind, id, span, attrs, token
             vis.visit_id(id);
             vis.visit_ident(ident);
             visit_opt(seg_args, |args| vis.visit_generic_args(args));
-            visit_thin_exprs(vis, call_args);
+            visit_exprs(vis, call_args);
             vis.visit_span(span);
         }
         ExprKind::Binary(binop, lhs, rhs) => {

compiler/rustc_ast/src/ptr.rs

@@ -1,209 +1,11 @@
-//! The AST pointer.
-//!
-//! Provides [`P<T>`][struct@P], an owned smart pointer.
-//!
-//! # Motivations and benefits
-//!
-//! * **Identity**: sharing AST nodes is problematic for the various analysis
-//!   passes (e.g., one may be able to bypass the borrow checker with a shared
-//!   `ExprKind::AddrOf` node taking a mutable borrow).
-//!
-//! * **Efficiency**: folding can reuse allocation space for `P<T>` and `Vec<T>`,
-//!   the latter even when the input and output types differ (as it would be the
-//!   case with arenas or a GADT AST using type parameters to toggle features).
-//!
-//! * **Maintainability**: `P<T>` provides an interface, which can remain fully
-//!   functional even if the implementation changes (using a special thread-local
-//!   heap, for example). Moreover, a switch to, e.g., `P<'a, T>` would be easy
-//!   and mostly automated.
-
-use std::fmt::{self, Debug, Display};
-use std::ops::{Deref, DerefMut};
-use std::{slice, vec};
-
-use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
-use rustc_serialize::{Decodable, Decoder, Encodable, Encoder};
-/// An owned smart pointer.
+/// A pointer type that uniquely owns a heap allocation of type T.
 ///
-/// See the [module level documentation][crate::ptr] for details.
-pub struct P<T: ?Sized> {
-    ptr: Box<T>,
-}
+/// This used to be its own type, but now it's just a typedef for `Box` and we are planning to
+/// remove it soon.
+pub type P<T> = Box<T>;
 
 /// Construct a `P<T>` from a `T` value.
 #[allow(non_snake_case)]
-pub fn P<T: 'static>(value: T) -> P<T> {
-    P { ptr: Box::new(value) }
-}
-
-impl<T: 'static> P<T> {
-    /// Move out of the pointer.
-    /// Intended for chaining transformations not covered by `map`.
-    pub fn and_then<U, F>(self, f: F) -> U
-    where
-        F: FnOnce(T) -> U,
-    {
-        f(*self.ptr)
-    }
-
-    /// Equivalent to `and_then(|x| x)`.
-    pub fn into_inner(self) -> T {
-        *self.ptr
-    }
-
-    /// Produce a new `P<T>` from `self` without reallocating.
-    pub fn map<F>(mut self, f: F) -> P<T>
-    where
-        F: FnOnce(T) -> T,
-    {
-        let x = f(*self.ptr);
-        *self.ptr = x;
-
-        self
-    }
-
-    /// Optionally produce a new `P<T>` from `self` without reallocating.
-    pub fn filter_map<F>(mut self, f: F) -> Option<P<T>>
-    where
-        F: FnOnce(T) -> Option<T>,
-    {
-        *self.ptr = f(*self.ptr)?;
-        Some(self)
-    }
-}
-
-impl<T: ?Sized> Deref for P<T> {
-    type Target = T;
-
-    fn deref(&self) -> &T {
-        &self.ptr
-    }
-}
-
-impl<T: ?Sized> DerefMut for P<T> {
-    fn deref_mut(&mut self) -> &mut T {
-        &mut self.ptr
-    }
-}
-
-impl<T: 'static + Clone> Clone for P<T> {
-    fn clone(&self) -> P<T> {
-        P((**self).clone())
-    }
-}
-
-impl<T: ?Sized + Debug> Debug for P<T> {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        Debug::fmt(&self.ptr, f)
-    }
-}
-
-impl<T: Display> Display for P<T> {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        Display::fmt(&**self, f)
-    }
-}
-
-impl<T> fmt::Pointer for P<T> {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        fmt::Pointer::fmt(&self.ptr, f)
-    }
-}
-
-impl<D: Decoder, T: 'static + Decodable<D>> Decodable<D> for P<T> {
-    fn decode(d: &mut D) -> P<T> {
-        P(Decodable::decode(d))
-    }
-}
-
-impl<S: Encoder, T: Encodable<S>> Encodable<S> for P<T> {
-    fn encode(&self, s: &mut S) {
-        (**self).encode(s);
-    }
-}
-
-impl<T> P<[T]> {
-    // FIXME(const-hack) make this const again
-    pub fn new() -> P<[T]> {
-        P { ptr: Box::default() }
-    }
-
-    #[inline(never)]
-    pub fn from_vec(v: Vec<T>) -> P<[T]> {
-        P { ptr: v.into_boxed_slice() }
-    }
-
-    #[inline(never)]
-    pub fn into_vec(self) -> Vec<T> {
-        self.ptr.into_vec()
-    }
-}
-
-impl<T> Default for P<[T]> {
-    /// Creates an empty `P<[T]>`.
-    fn default() -> P<[T]> {
-        P::new()
-    }
-}
-
-impl<T: Clone> Clone for P<[T]> {
-    fn clone(&self) -> P<[T]> {
-        P::from_vec(self.to_vec())
-    }
-}
-
-impl<T> From<Vec<T>> for P<[T]> {
-    fn from(v: Vec<T>) -> Self {
-        P::from_vec(v)
-    }
-}
-
-impl<T> From<P<[T]>> for Vec<T> {
-    fn from(val: P<[T]>) -> Self {
-        val.into_vec()
-    }
-}
-
-impl<T> FromIterator<T> for P<[T]> {
-    fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> P<[T]> {
-        P::from_vec(iter.into_iter().collect())
-    }
-}
-
-impl<T> IntoIterator for P<[T]> {
-    type Item = T;
-    type IntoIter = vec::IntoIter<T>;
-
-    fn into_iter(self) -> Self::IntoIter {
-        self.into_vec().into_iter()
-    }
-}
-
-impl<'a, T> IntoIterator for &'a P<[T]> {
-    type Item = &'a T;
-    type IntoIter = slice::Iter<'a, T>;
-    fn into_iter(self) -> Self::IntoIter {
-        self.ptr.iter()
-    }
-}
-
-impl<S: Encoder, T: Encodable<S>> Encodable<S> for P<[T]> {
-    fn encode(&self, s: &mut S) {
-        Encodable::encode(&**self, s);
-    }
-}
-
-impl<D: Decoder, T: Decodable<D>> Decodable<D> for P<[T]> {
-    fn decode(d: &mut D) -> P<[T]> {
-        P::from_vec(Decodable::decode(d))
-    }
-}
-
-impl<CTX, T> HashStable<CTX> for P<T>
-where
-    T: ?Sized + HashStable<CTX>,
-{
-    fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
-        (**self).hash_stable(hcx, hasher);
-    }
+pub fn P<T>(value: T) -> P<T> {
+    Box::new(value)
 }

compiler/rustc_ast/src/tokenstream.rs

@@ -57,7 +57,9 @@ impl TokenTree {
         match (self, other) {
             (TokenTree::Token(token, _), TokenTree::Token(token2, _)) => token.kind == token2.kind,
             (TokenTree::Delimited(.., delim, tts), TokenTree::Delimited(.., delim2, tts2)) => {
-                delim == delim2 && tts.eq_unspanned(tts2)
+                delim == delim2
+                    && tts.len() == tts2.len()
+                    && tts.iter().zip(tts2.iter()).all(|(a, b)| a.eq_unspanned(b))
             }
             _ => false,
         }
@@ -694,18 +696,6 @@ impl TokenStream {
         TokenStreamIter::new(self)
     }
 
-    /// Compares two `TokenStream`s, checking equality without regarding span information.
-    pub fn eq_unspanned(&self, other: &TokenStream) -> bool {
-        let mut iter1 = self.iter();
-        let mut iter2 = other.iter();
-        for (tt1, tt2) in iter::zip(&mut iter1, &mut iter2) {
-            if !tt1.eq_unspanned(tt2) {
-                return false;
-            }
-        }
-        iter1.next().is_none() && iter2.next().is_none()
-    }
-
     /// Create a token stream containing a single token with alone spacing. The
     /// spacing used for the final token in a constructed stream doesn't matter
     /// because it's never used. In practice we arbitrarily use

compiler/rustc_ast/src/visit.rs

@@ -121,6 +121,10 @@ pub enum LifetimeCtxt {
 /// explicitly, you need to override each method. (And you also need
 /// to monitor future changes to `Visitor` in case a new method with a
 /// new default implementation gets introduced.)
+///
+/// Every `walk_*` method uses deconstruction to access fields of structs and
+/// enums. This will result in a compile error if a field is added, which makes
+/// it more likely the appropriate visit call will be added for it.
 pub trait Visitor<'ast>: Sized {
     /// The result type of the `visit_*` methods. Can be either `()`,
     /// or `ControlFlow<T>`.
@@ -210,14 +214,11 @@ pub trait Visitor<'ast>: Sized {
         walk_poly_trait_ref(self, t)
     }
     fn visit_variant_data(&mut self, s: &'ast VariantData) -> Self::Result {
-        walk_struct_def(self, s)
+        walk_variant_data(self, s)
     }
     fn visit_field_def(&mut self, s: &'ast FieldDef) -> Self::Result {
         walk_field_def(self, s)
     }
-    fn visit_enum_def(&mut self, enum_definition: &'ast EnumDef) -> Self::Result {
-        walk_enum_def(self, enum_definition)
-    }
     fn visit_variant(&mut self, v: &'ast Variant) -> Self::Result {
         walk_variant(self, v)
     }
@@ -233,19 +234,21 @@ pub trait Visitor<'ast>: Sized {
     fn visit_mac_call(&mut self, mac: &'ast MacCall) -> Self::Result {
         walk_mac(self, mac)
     }
-    fn visit_macro_def(&mut self, _mac: &'ast MacroDef, _id: NodeId) -> Self::Result {
+    fn visit_id(&mut self, _id: NodeId) -> Self::Result {
         Self::Result::output()
     }
-    fn visit_path(&mut self, path: &'ast Path, _id: NodeId) -> Self::Result {
+    fn visit_macro_def(&mut self, _mac: &'ast MacroDef) -> Self::Result {
+        Self::Result::output()
+    }
+    fn visit_path(&mut self, path: &'ast Path) -> Self::Result {
         walk_path(self, path)
     }
-    fn visit_use_tree(
-        &mut self,
-        use_tree: &'ast UseTree,
-        id: NodeId,
-        _nested: bool,
-    ) -> Self::Result {
-        walk_use_tree(self, use_tree, id)
+    fn visit_use_tree(&mut self, use_tree: &'ast UseTree) -> Self::Result {
+        walk_use_tree(self, use_tree)
+    }
+    fn visit_nested_use_tree(&mut self, use_tree: &'ast UseTree, id: NodeId) -> Self::Result {
+        try_visit!(self.visit_id(id));
+        self.visit_use_tree(use_tree)
     }
     fn visit_path_segment(&mut self, path_segment: &'ast PathSegment) -> Self::Result {
         walk_path_segment(self, path_segment)
@@ -295,8 +298,8 @@ pub trait Visitor<'ast>: Sized {
     fn visit_capture_by(&mut self, _capture_by: &'ast CaptureBy) -> Self::Result {
         Self::Result::output()
     }
-    fn visit_coroutine_kind(&mut self, _coroutine_kind: &'ast CoroutineKind) -> Self::Result {
-        Self::Result::output()
+    fn visit_coroutine_kind(&mut self, coroutine_kind: &'ast CoroutineKind) -> Self::Result {
+        walk_coroutine_kind(self, coroutine_kind)
     }
     fn visit_fn_decl(&mut self, fn_decl: &'ast FnDecl) -> Self::Result {
         walk_fn_decl(self, fn_decl)
@@ -334,17 +337,14 @@ macro_rules! common_visitor_and_walkers {
             $(${ignore($lt)}V::Result::output())?
         }
 
-        // this is only used by the MutVisitor. We include this symmetry here to make writing other functions easier
+        /// helper since `Visitor` wants `NodeId` but `MutVisitor` wants `&mut NodeId`
         $(${ignore($lt)}
-            #[expect(unused, rustc::pass_by_value)]
-            #[inline]
+            #[expect(rustc::pass_by_value)]
         )?
+        #[inline]
         fn visit_id<$($lt,)? V: $Visitor$(<$lt>)?>(visitor: &mut V, id: &$($lt)? $($mut)? NodeId) $(-> <V as Visitor<$lt>>::Result)? {
-            $(
-                ${ignore($mut)}
-                visitor.visit_id(id);
-            )?
-            $(${ignore($lt)}V::Result::output())?
+            // deref `&NodeId` into `NodeId` only for `Visitor`
+            visitor.visit_id( $(${ignore($lt)} * )? id)
         }
 
         // this is only used by the MutVisitor. We include this symmetry here to make writing other functions easier
@@ -374,13 +374,39 @@ macro_rules! common_visitor_and_walkers {
             }
         }
 
-        fn visit_polarity<$($lt,)? V: $Visitor$(<$lt>)?>(vis: &mut V, polarity: &$($lt)? $($mut)? ImplPolarity) $(-> <V as Visitor<$lt>>::Result)? {
+        fn visit_polarity<$($lt,)? V: $Visitor$(<$lt>)?>(
+            vis: &mut V,
+            polarity: &$($lt)? $($mut)? ImplPolarity,
+        ) $(-> <V as Visitor<$lt>>::Result)? {
             match polarity {
                 ImplPolarity::Positive => { $(<V as Visitor<$lt>>::Result::output())? }
                 ImplPolarity::Negative(span) => visit_span(vis, span),
             }
         }
 
+        $(${ignore($lt)}
+            #[inline]
+        )?
+        fn visit_modifiers<$($lt,)? V: $Visitor$(<$lt>)?>(
+            vis: &mut V,
+            m: &$($lt)? $($mut)? TraitBoundModifiers
+        ) $(-> <V as Visitor<$lt>>::Result)? {
+            let TraitBoundModifiers { constness, asyncness, polarity } = m;
+            match constness {
+                BoundConstness::Never => {}
+                BoundConstness::Always(span) | BoundConstness::Maybe(span) => try_visit!(visit_span(vis, span)),
+            }
+            match asyncness {
+                BoundAsyncness::Normal => {}
+                BoundAsyncness::Async(span) => try_visit!(visit_span(vis, span)),
+            }
+            match polarity {
+                BoundPolarity::Positive => {}
+                BoundPolarity::Negative(span) | BoundPolarity::Maybe(span) => try_visit!(visit_span(vis, span)),
+            }
+            $(<V as Visitor<$lt>>::Result::output())?
+        }
+
         fn visit_bounds<$($lt,)? V: $Visitor$(<$lt>)?>(visitor: &mut V, bounds: &$($lt)? $($mut)? GenericBounds, ctxt: BoundKind) $(-> <V as Visitor<$lt>>::Result)? {
             walk_list!(visitor, visit_param_bound, bounds, ctxt);
             $(<V as Visitor<$lt>>::Result::output())?
@@ -442,8 +468,7 @@ macro_rules! common_visitor_and_walkers {
             ) $(-> <V as Visitor<$lt>>::Result)? {
                 match self {
                     ItemKind::ExternCrate(_orig_name, ident) => vis.visit_ident(ident),
-                    // FIXME(fee1-dead): look into this weird assymetry
-                    ItemKind::Use(use_tree) => vis.visit_use_tree(use_tree$(${ignore($lt)}, id, false)?),
+                    ItemKind::Use(use_tree) => vis.visit_use_tree(use_tree),
                     ItemKind::Static(box StaticItem {
                         ident,
                         ty,
@@ -474,12 +499,7 @@ macro_rules! common_visitor_and_walkers {
                                 ModSpans { inner_span, inject_use_span },
                                 _,
                             ) => {
-                                $(${ignore($mut)}
-                                    items.flat_map_in_place(|item| vis.flat_map_item(item));
-                                )?
-                                $(${ignore($lt)}
-                                    walk_list!(vis, visit_item, items);
-                                )?
+                                try_visit!(visit_items(vis, items));
                                 try_visit!(visit_span(vis, inner_span));
                                 try_visit!(visit_span(vis, inject_use_span));
                             }
@@ -511,10 +531,7 @@ macro_rules! common_visitor_and_walkers {
                     ItemKind::Enum(ident, generics, enum_definition) => {
                         try_visit!(vis.visit_ident(ident));
                         try_visit!(vis.visit_generics(generics));
-                        $(${ignore($mut)}
-                            enum_definition.variants.flat_map_in_place(|variant| vis.flat_map_variant(variant));
-                        )?
-                        $(${ignore($lt)}vis.visit_enum_def(enum_definition))?
+                        visit_variants(vis, &$($mut)? enum_definition.variants)
                     }
                     ItemKind::Struct(ident, generics, variant_data)
                     | ItemKind::Union(ident, generics, variant_data) => {
@@ -539,35 +556,14 @@ macro_rules! common_visitor_and_walkers {
                         try_visit!(visit_polarity(vis, polarity));
                         visit_opt!(vis, visit_trait_ref, of_trait);
                         try_visit!(vis.visit_ty(self_ty));
-                        $(${ignore($mut)}
-                            items.flat_map_in_place(|item| {
-                                vis.flat_map_assoc_item(item, AssocCtxt::Impl { of_trait: of_trait.is_some() })
-                            });
-                        )?
-                        $(${ignore($lt)}
-                            walk_list!(
-                                vis,
-                                visit_assoc_item,
-                                items,
-                                AssocCtxt::Impl { of_trait: of_trait.is_some() }
-                            );
-                            <V as Visitor<$lt>>::Result::output()
-                        )?
+                        visit_assoc_items(vis, items, AssocCtxt::Impl { of_trait: of_trait.is_some() })
                     }
                     ItemKind::Trait(box Trait { safety, is_auto: _, ident, generics, bounds, items }) => {
                         try_visit!(visit_safety(vis, safety));
                         try_visit!(vis.visit_ident(ident));
                         try_visit!(vis.visit_generics(generics));
                         try_visit!(visit_bounds(vis, bounds, BoundKind::Bound));
-                        $(${ignore($mut)}
-                            items.flat_map_in_place(|item| {
-                                vis.flat_map_assoc_item(item, AssocCtxt::Trait)
-                            });
-                        )?
-                        $(${ignore($lt)}
-                            walk_list!(vis, visit_assoc_item, items, AssocCtxt::Trait);
-                            <V as Visitor<$lt>>::Result::output()
-                        )?
+                        visit_assoc_items(vis, items, AssocCtxt::Trait)
                     }
                     ItemKind::TraitAlias(ident, generics, bounds) => {
                         try_visit!(vis.visit_ident(ident));
@@ -577,8 +573,7 @@ macro_rules! common_visitor_and_walkers {
                     ItemKind::MacCall(m) => vis.visit_mac_call(m),
                     ItemKind::MacroDef(ident, def) => {
                         try_visit!(vis.visit_ident(ident));
-                        // FIXME(fee1-dead) assymetry
-                        vis.visit_macro_def(def$(${ignore($lt)}, id)?)
+                        vis.visit_macro_def(def)
                     }
                     ItemKind::Delegation(box Delegation {
                         id,
@@ -591,7 +586,7 @@ macro_rules! common_visitor_and_walkers {
                     }) => {
                         try_visit!(visit_id(vis, id));
                         try_visit!(vis.visit_qself(qself));
-                        try_visit!(vis.visit_path(path$(${ignore($lt)}, *id)?));
+                        try_visit!(vis.visit_path(path));
                         try_visit!(vis.visit_ident(ident));
                         visit_opt!(vis, visit_ident, rename);
                         visit_opt!(vis, visit_block, body);
@@ -599,7 +594,7 @@ macro_rules! common_visitor_and_walkers {
                     }
                     ItemKind::DelegationMac(box DelegationMac { qself, prefix, suffixes, body }) => {
                         try_visit!(vis.visit_qself(qself));
-                        try_visit!(vis.visit_path(prefix$(${ignore($lt)}, id)?));
+                        try_visit!(vis.visit_path(prefix));
                         if let Some(suffixes) = suffixes {
                             for (ident, rename) in suffixes {
                                 try_visit!(vis.visit_ident(ident));
@@ -613,7 +608,10 @@ macro_rules! common_visitor_and_walkers {
             }
         }
 
-        fn walk_const_item<$($lt,)? V: $Visitor$(<$lt>)?>(vis: &mut V, item: &$($lt)? $($mut)? ConstItem) $(-> <V as Visitor<$lt>>::Result)? {
+        fn walk_const_item<$($lt,)? V: $Visitor$(<$lt>)?>(
+            vis: &mut V,
+            item: &$($lt)? $($mut)? ConstItem,
+        ) $(-> <V as Visitor<$lt>>::Result)? {
             let ConstItem { defaultness, ident, generics, ty, expr, define_opaque } = item;
             try_visit!(visit_defaultness(vis, defaultness));
             try_visit!(vis.visit_ident(ident));
@@ -626,13 +624,7 @@ macro_rules! common_visitor_and_walkers {
         fn walk_foreign_mod<$($lt,)? V: $Visitor$(<$lt>)?>(vis: &mut V, foreign_mod: &$($lt)? $($mut)? ForeignMod) $(-> <V as Visitor<$lt>>::Result)? {
             let ForeignMod { extern_span: _, safety, abi: _, items } = foreign_mod;
             try_visit!(visit_safety(vis, safety));
-            $(${ignore($mut)}
-                items.flat_map_in_place(|item| vis.flat_map_foreign_item(item));
-            )?
-            $(
-                walk_list!(vis, visit_foreign_item, items);
-                <V as Visitor<$lt>>::Result::output()
-            )?
+            visit_foreign_items(vis, items)
         }
 
         fn walk_define_opaques<$($lt,)? V: $Visitor$(<$lt>)?>(
@@ -642,8 +634,7 @@ macro_rules! common_visitor_and_walkers {
             if let Some(define_opaque) = define_opaque {
                 for (id, path) in define_opaque {
                     try_visit!(visit_id(visitor, id));
-                    // FIXME(fee1-dead): look into this weird assymetry
-                    try_visit!(visitor.visit_path(path$(${ignore($lt)}, *id)?));
+                    try_visit!(visitor.visit_path(path));
                 }
             }
             $(<V as Visitor<$lt>>::Result::output())?
@@ -699,7 +690,7 @@ macro_rules! common_visitor_and_walkers {
                     }) => {
                         try_visit!(visit_id(vis, id));
                         try_visit!(vis.visit_qself(qself));
-                        try_visit!(vis.visit_path(path $(${ignore($lt)}, *id)?));
+                        try_visit!(vis.visit_path(path));
                         try_visit!(vis.visit_ident(ident));
                         visit_opt!(vis, visit_ident, rename);
                         visit_opt!(vis, visit_block, body);
@@ -707,7 +698,7 @@ macro_rules! common_visitor_and_walkers {
                     }
                     AssocItemKind::DelegationMac(box DelegationMac { qself, prefix, suffixes, body }) => {
                         try_visit!(vis.visit_qself(qself));
-                        try_visit!(vis.visit_path(prefix$(${ignore($lt)}, id)?));
+                        try_visit!(vis.visit_path(prefix));
                         if let Some(suffixes) = suffixes {
                             for (ident, rename) in suffixes {
                                 try_visit!(vis.visit_ident(ident));
@@ -773,188 +764,356 @@ macro_rules! common_visitor_and_walkers {
                 }
             }
         }
+
+        fn walk_coroutine_kind<$($lt,)? V: $Visitor$(<$lt>)?>(
+            vis: &mut V,
+            coroutine_kind: &$($lt)? $($mut)? CoroutineKind,
+        ) $(-> <V as Visitor<$lt>>::Result)? {
+            let (CoroutineKind::Async { span, closure_id, return_impl_trait_id }
+                | CoroutineKind::Gen { span, closure_id, return_impl_trait_id }
+                | CoroutineKind::AsyncGen { span, closure_id, return_impl_trait_id })
+                = coroutine_kind;
+            try_visit!(visit_id(vis, closure_id));
+            try_visit!(visit_id(vis, return_impl_trait_id));
+            visit_span(vis, span)
+        }
+
+        pub fn walk_pat<$($lt,)? V: $Visitor$(<$lt>)?>(
+            vis: &mut V,
+            pattern: &$($lt)? $($mut)? Pat
+        ) $(-> <V as Visitor<$lt>>::Result)? {
+            let Pat { id, kind, span, tokens: _ } = pattern;
+            try_visit!(visit_id(vis, id));
+            match kind {
+                PatKind::Err(_guar) => {}
+                PatKind::Missing | PatKind::Wild | PatKind::Rest | PatKind::Never => {}
+                PatKind::Ident(_bmode, ident, optional_subpattern) => {
+                    try_visit!(vis.visit_ident(ident));
+                    visit_opt!(vis, visit_pat, optional_subpattern);
+                }
+                PatKind::Expr(expression) => try_visit!(vis.visit_expr(expression)),
+                PatKind::TupleStruct(opt_qself, path, elems) => {
+                    try_visit!(vis.visit_qself(opt_qself));
+                    try_visit!(vis.visit_path(path));
+                    walk_list!(vis, visit_pat, elems);
+                }
+                PatKind::Path(opt_qself, path) => {
+                    try_visit!(vis.visit_qself(opt_qself));
+                    try_visit!(vis.visit_path(path))
+                }
+                PatKind::Struct(opt_qself, path, fields, _rest) => {
+                    try_visit!(vis.visit_qself(opt_qself));
+                    try_visit!(vis.visit_path(path));
+                    try_visit!(visit_pat_fields(vis, fields));
+                }
+                PatKind::Box(subpattern) | PatKind::Deref(subpattern) | PatKind::Paren(subpattern) => {
+                    try_visit!(vis.visit_pat(subpattern));
+                }
+                PatKind::Ref(subpattern, _ /*mutbl*/) => {
+                    try_visit!(vis.visit_pat(subpattern));
+                }
+                PatKind::Range(lower_bound, upper_bound, _end) => {
+                    visit_opt!(vis, visit_expr, lower_bound);
+                    visit_opt!(vis, visit_expr, upper_bound);
+                    try_visit!(visit_span(vis, span));
+                }
+                PatKind::Guard(subpattern, guard_condition) => {
+                    try_visit!(vis.visit_pat(subpattern));
+                    try_visit!(vis.visit_expr(guard_condition));
+                }
+                PatKind::Tuple(elems) | PatKind::Slice(elems) | PatKind::Or(elems) => {
+                    walk_list!(vis, visit_pat, elems);
+                }
+                PatKind::MacCall(mac) => try_visit!(vis.visit_mac_call(mac)),
+            }
+            visit_span(vis, span)
+        }
+
+        pub fn walk_anon_const<$($lt,)? V: $Visitor$(<$lt>)?>(
+            vis: &mut V,
+            constant: &$($lt)? $($mut)? AnonConst,
+        ) $(-> <V as Visitor<$lt>>::Result)? {
+            let AnonConst { id, value } = constant;
+            try_visit!(visit_id(vis, id));
+            vis.visit_expr(value)
+        }
+
+        pub fn walk_path_segment<$($lt,)? V: $Visitor$(<$lt>)?>(
+            vis: &mut V,
+            segment: &$($lt)? $($mut)? PathSegment,
+        ) $(-> <V as Visitor<$lt>>::Result)? {
+            let PathSegment { ident, id, args } = segment;
+            try_visit!(visit_id(vis, id));
+            try_visit!(vis.visit_ident(ident));
+            visit_opt!(vis, visit_generic_args, args);
+            $(<V as Visitor<$lt>>::Result::output())?
+        }
+
+        pub fn walk_block<$($lt,)? V: $Visitor$(<$lt>)?>(
+            vis: &mut V,
+            block: &$($lt)? $($mut)? Block
+        ) $(-> <V as Visitor<$lt>>::Result)? {
+            let Block { stmts, id, rules: _, span, tokens: _ } = block;
+            try_visit!(visit_id(vis, id));
+            try_visit!(visit_stmts(vis, stmts));
+            visit_span(vis, span)
+        }
+
+
+        pub fn walk_ty<$($lt,)? V: $Visitor$(<$lt>)?>(
+            vis: &mut V, ty: &$($lt)? $($mut)? Ty
+        ) $(-> <V as Visitor<$lt>>::Result)? {
+            let Ty { id, kind, span, tokens: _ } = ty;
+            try_visit!(visit_id(vis, id));
+            match kind {
+                TyKind::Err(_guar) => {}
+                TyKind::Infer | TyKind::ImplicitSelf | TyKind::Dummy | TyKind::Never | TyKind::CVarArgs => {}
+                TyKind::Slice(ty) | TyKind::Paren(ty) => try_visit!(vis.visit_ty(ty)),
+                TyKind::Ptr(MutTy { ty, mutbl: _ }) => try_visit!(vis.visit_ty(ty)),
+                TyKind::Ref(opt_lifetime, MutTy { ty, mutbl: _ })
+                | TyKind::PinnedRef(opt_lifetime, MutTy { ty, mutbl: _ }) => {
+                    // FIXME(fee1-dead) asymmetry
+                    visit_opt!(vis, visit_lifetime, opt_lifetime$(${ignore($lt)}, LifetimeCtxt::Ref)?);
+                    try_visit!(vis.visit_ty(ty));
+                }
+                TyKind::Tup(tuple_element_types) => {
+                    walk_list!(vis, visit_ty, tuple_element_types);
+                }
+                TyKind::BareFn(function_declaration) => {
+                    let BareFnTy { safety, ext: _, generic_params, decl, decl_span } =
+                        &$($mut)? **function_declaration;
+                    visit_safety(vis, safety);
+                    try_visit!(visit_generic_params(vis, generic_params));
+                    try_visit!(vis.visit_fn_decl(decl));
+                    try_visit!(visit_span(vis, decl_span));
+                }
+                TyKind::UnsafeBinder(binder) => {
+                    try_visit!(visit_generic_params(vis, &$($mut)? binder.generic_params));
+                    try_visit!(vis.visit_ty(&$($mut)? binder.inner_ty));
+                }
+                TyKind::Path(maybe_qself, path) => {
+                    try_visit!(vis.visit_qself(maybe_qself));
+                    try_visit!(vis.visit_path(path));
+                }
+                TyKind::Pat(ty, pat) => {
+                    try_visit!(vis.visit_ty(ty));
+                    try_visit!(vis.visit_ty_pat(pat));
+                }
+                TyKind::Array(ty, length) => {
+                    try_visit!(vis.visit_ty(ty));
+                    try_visit!(vis.visit_anon_const(length));
+                }
+                TyKind::TraitObject(bounds, _syntax) => {
+                    walk_list!(vis, visit_param_bound, bounds, BoundKind::TraitObject);
+                }
+                TyKind::ImplTrait(id, bounds) => {
+                    try_visit!(visit_id(vis, id));
+                    walk_list!(vis, visit_param_bound, bounds, BoundKind::Impl);
+                }
+                TyKind::Typeof(expression) => try_visit!(vis.visit_anon_const(expression)),
+
+                TyKind::MacCall(mac) => try_visit!(vis.visit_mac_call(mac)),
+            }
+            visit_span(vis, span)
+        }
+
+        pub fn walk_crate<$($lt,)? V: $Visitor$(<$lt>)?>(
+            vis: &mut V,
+            krate: &$($lt)? $($mut)? Crate,
+        ) $(-> <V as Visitor<$lt>>::Result)? {
+            let Crate { attrs, items, spans, id, is_placeholder: _ } = krate;
+            try_visit!(visit_id(vis, id));
+            walk_list!(vis, visit_attribute, attrs);
+            try_visit!(visit_items(vis, items));
+            let ModSpans { inner_span, inject_use_span } = spans;
+            try_visit!(visit_span(vis, inner_span));
+            visit_span(vis, inject_use_span)
+        }
+
+        pub fn walk_local<$($lt,)? V: $Visitor$(<$lt>)?>(
+            vis: &mut V,
+            local: &$($lt)? $($mut)? Local,
+        ) $(-> <V as Visitor<$lt>>::Result)? {
+            let Local { id, super_, pat, ty, kind, span, colon_sp, attrs, tokens: _ } = local;
+            if let Some(sp) = super_ {
+                try_visit!(visit_span(vis, sp));
+            }
+            try_visit!(visit_id(vis, id));
+            walk_list!(vis, visit_attribute, attrs);
+            try_visit!(vis.visit_pat(pat));
+            visit_opt!(vis, visit_ty, ty);
+            match kind {
+                LocalKind::Decl => {}
+                LocalKind::Init(init) => {
+                    try_visit!(vis.visit_expr(init))
+                }
+                LocalKind::InitElse(init, els) => {
+                    try_visit!(vis.visit_expr(init));
+                    try_visit!(vis.visit_block(els));
+                }
+            }
+            if let Some(sp) = colon_sp {
+                try_visit!(visit_span(vis, sp));
+            }
+            visit_span(vis, span)
+        }
+
+        pub fn walk_poly_trait_ref<$($lt,)? V: $Visitor$(<$lt>)?>(
+            vis: &mut V,
+            p: &$($lt)? $($mut)? PolyTraitRef,
+        ) $(-> <V as Visitor<$lt>>::Result)? {
+            let PolyTraitRef { bound_generic_params, modifiers, trait_ref, span } = p;
+            try_visit!(visit_modifiers(vis, modifiers));
+            try_visit!(visit_generic_params(vis, bound_generic_params));
+            try_visit!(vis.visit_trait_ref(trait_ref));
+            visit_span(vis, span)
+        }
+
+        pub fn walk_trait_ref<$($lt,)? V: $Visitor$(<$lt>)?>(
+            vis: &mut V,
+            TraitRef { path, ref_id }: &$($lt)? $($mut)? TraitRef,
+        ) $(-> <V as Visitor<$lt>>::Result)? {
+            try_visit!(vis.visit_path(path));
+            visit_id(vis, ref_id)
+        }
+
+        pub fn walk_variant<$($lt,)? V: $Visitor$(<$lt>)?>(
+            vis: &mut V,
+            variant: &$($lt)? $($mut)? Variant,
+        ) $(-> <V as Visitor<$lt>>::Result)? {
+            let Variant { attrs, id, span, vis: visibility, ident, data, disr_expr, is_placeholder: _ } = variant;
+            try_visit!(visit_id(vis, id));
+            walk_list!(vis, visit_attribute, attrs);
+            try_visit!(vis.visit_vis(visibility));
+            try_visit!(vis.visit_ident(ident));
+            try_visit!(vis.visit_variant_data(data));
+            $(${ignore($lt)} visit_opt!(vis, visit_variant_discr, disr_expr); )?
+            $(${ignore($mut)} visit_opt!(vis, visit_anon_const, disr_expr); )?
+            visit_span(vis, span)
+        }
+
+        pub fn walk_expr_field<$($lt,)? V: $Visitor$(<$lt>)?>(
+            vis: &mut V,
+            f: &$($lt)? $($mut)? ExprField,
+        ) $(-> <V as Visitor<$lt>>::Result)? {
+            let ExprField { attrs, id, span, ident, expr, is_shorthand: _, is_placeholder: _ } = f;
+            try_visit!(visit_id(vis, id));
+            walk_list!(vis, visit_attribute, attrs);
+            try_visit!(vis.visit_ident(ident));
+            try_visit!(vis.visit_expr(expr));
+            visit_span(vis, span)
+        }
+
+        pub fn walk_pat_field<$($lt,)? V: $Visitor$(<$lt>)?>(
+            vis: &mut V,
+            fp: &$($lt)? $($mut)? PatField,
+        ) $(-> <V as Visitor<$lt>>::Result)? {
+            let PatField { ident, pat, is_shorthand: _, attrs, id, span, is_placeholder: _ } = fp;
+            try_visit!(visit_id(vis, id));
+            walk_list!(vis, visit_attribute, attrs);
+            try_visit!(vis.visit_ident(ident));
+            try_visit!(vis.visit_pat(pat));
+            visit_span(vis, span)
+        }
+
+        pub fn walk_ty_pat<$($lt,)? V: $Visitor$(<$lt>)?>(
+            vis: &mut V,
+            tp: &$($lt)? $($mut)? TyPat,
+        ) $(-> <V as Visitor<$lt>>::Result)? {
+            let TyPat { id, kind, span, tokens: _ } = tp;
+            try_visit!(visit_id(vis, id));
+            match kind {
+                TyPatKind::Range(start, end, _include_end) => {
+                    visit_opt!(vis, visit_anon_const, start);
+                    visit_opt!(vis, visit_anon_const, end);
+                }
+                TyPatKind::Or(variants) => walk_list!(vis, visit_ty_pat, variants),
+                TyPatKind::Err(_) => {}
+            }
+            visit_span(vis, span)
+        }
+
+        fn walk_qself<$($lt,)? V: $Visitor$(<$lt>)?>(
+            vis: &mut V,
+            qself: &$($lt)? $($mut)? Option<P<QSelf>>,
+        ) $(-> <V as Visitor<$lt>>::Result)? {
+            if let Some(qself) = qself {
+                let QSelf { ty, path_span, position: _ } = &$($mut)? **qself;
+                try_visit!(vis.visit_ty(ty));
+                try_visit!(visit_span(vis, path_span));
+            }
+            $(<V as Visitor<$lt>>::Result::output())?
+        }
+
+        pub fn walk_path<$($lt,)? V: $Visitor$(<$lt>)?>(
+            vis: &mut V,
+            path: &$($lt)? $($mut)? Path,
+        ) $(-> <V as Visitor<$lt>>::Result)? {
+            let Path { span, segments, tokens: _ } = path;
+            walk_list!(vis, visit_path_segment, segments);
+            visit_span(vis, span)
+        }
+
+        pub fn walk_use_tree<$($lt,)? V: $Visitor$(<$lt>)?>(
+            vis: &mut V,
+            use_tree: &$($lt)? $($mut)? UseTree,
+        ) $(-> <V as Visitor<$lt>>::Result)? {
+            let UseTree { prefix, kind, span } = use_tree;
+            try_visit!(vis.visit_path(prefix));
+            match kind {
+                UseTreeKind::Simple(rename) => {
+                    // The extra IDs are handled during AST lowering.
+                    visit_opt!(vis, visit_ident, rename);
+                }
+                UseTreeKind::Glob => {}
+                UseTreeKind::Nested { items, span } => {
+                    for (nested_tree, nested_id) in items {
+                        try_visit!(visit_nested_use_tree(vis, nested_tree, nested_id));
+                    }
+                    try_visit!(visit_span(vis, span));
+                }
+            }
+            visit_span(vis, span)
+        }
     };
 }
 
 common_visitor_and_walkers!(Visitor<'a>);
 
-pub fn walk_crate<'a, V: Visitor<'a>>(visitor: &mut V, krate: &'a Crate) -> V::Result {
-    let Crate { attrs, items, spans: _, id: _, is_placeholder: _ } = krate;
-    walk_list!(visitor, visit_attribute, attrs);
-    walk_list!(visitor, visit_item, items);
-    V::Result::output()
-}
-
-pub fn walk_local<'a, V: Visitor<'a>>(visitor: &mut V, local: &'a Local) -> V::Result {
-    let Local { id: _, super_: _, pat, ty, kind, span: _, colon_sp: _, attrs, tokens: _ } = local;
-    walk_list!(visitor, visit_attribute, attrs);
-    try_visit!(visitor.visit_pat(pat));
-    visit_opt!(visitor, visit_ty, ty);
-    if let Some((init, els)) = kind.init_else_opt() {
-        try_visit!(visitor.visit_expr(init));
-        visit_opt!(visitor, visit_block, els);
-    }
-    V::Result::output()
-}
-
-pub fn walk_poly_trait_ref<'a, V>(visitor: &mut V, trait_ref: &'a PolyTraitRef) -> V::Result
-where
-    V: Visitor<'a>,
-{
-    let PolyTraitRef { bound_generic_params, modifiers: _, trait_ref, span: _ } = trait_ref;
-    walk_list!(visitor, visit_generic_param, bound_generic_params);
-    visitor.visit_trait_ref(trait_ref)
-}
-
-pub fn walk_trait_ref<'a, V: Visitor<'a>>(visitor: &mut V, trait_ref: &'a TraitRef) -> V::Result {
-    let TraitRef { path, ref_id } = trait_ref;
-    visitor.visit_path(path, *ref_id)
-}
-
-pub fn walk_enum_def<'a, V: Visitor<'a>>(
-    visitor: &mut V,
-    EnumDef { variants }: &'a EnumDef,
-) -> V::Result {
-    walk_list!(visitor, visit_variant, variants);
-    V::Result::output()
-}
-
-pub fn walk_variant<'a, V: Visitor<'a>>(visitor: &mut V, variant: &'a Variant) -> V::Result
-where
-    V: Visitor<'a>,
-{
-    let Variant { attrs, id: _, span: _, vis, ident, data, disr_expr, is_placeholder: _ } = variant;
-    walk_list!(visitor, visit_attribute, attrs);
-    try_visit!(visitor.visit_vis(vis));
-    try_visit!(visitor.visit_ident(ident));
-    try_visit!(visitor.visit_variant_data(data));
-    visit_opt!(visitor, visit_variant_discr, disr_expr);
-    V::Result::output()
-}
-
-pub fn walk_expr_field<'a, V: Visitor<'a>>(visitor: &mut V, f: &'a ExprField) -> V::Result {
-    let ExprField { attrs, id: _, span: _, ident, expr, is_shorthand: _, is_placeholder: _ } = f;
-    walk_list!(visitor, visit_attribute, attrs);
-    try_visit!(visitor.visit_ident(ident));
-    try_visit!(visitor.visit_expr(expr));
-    V::Result::output()
-}
-
-pub fn walk_pat_field<'a, V: Visitor<'a>>(visitor: &mut V, fp: &'a PatField) -> V::Result {
-    let PatField { ident, pat, is_shorthand: _, attrs, id: _, span: _, is_placeholder: _ } = fp;
-    walk_list!(visitor, visit_attribute, attrs);
-    try_visit!(visitor.visit_ident(ident));
-    try_visit!(visitor.visit_pat(pat));
-    V::Result::output()
-}
-
-pub fn walk_ty<'a, V: Visitor<'a>>(visitor: &mut V, typ: &'a Ty) -> V::Result {
-    let Ty { id, kind, span: _, tokens: _ } = typ;
-    match kind {
-        TyKind::Slice(ty) | TyKind::Paren(ty) => try_visit!(visitor.visit_ty(ty)),
-        TyKind::Ptr(MutTy { ty, mutbl: _ }) => try_visit!(visitor.visit_ty(ty)),
-        TyKind::Ref(opt_lifetime, MutTy { ty, mutbl: _ })
-        | TyKind::PinnedRef(opt_lifetime, MutTy { ty, mutbl: _ }) => {
-            visit_opt!(visitor, visit_lifetime, opt_lifetime, LifetimeCtxt::Ref);
-            try_visit!(visitor.visit_ty(ty));
-        }
-        TyKind::Tup(tuple_element_types) => {
-            walk_list!(visitor, visit_ty, tuple_element_types);
-        }
-        TyKind::BareFn(function_declaration) => {
-            let BareFnTy { safety: _, ext: _, generic_params, decl, decl_span: _ } =
-                &**function_declaration;
-            walk_list!(visitor, visit_generic_param, generic_params);
-            try_visit!(visitor.visit_fn_decl(decl));
-        }
-        TyKind::UnsafeBinder(binder) => {
-            walk_list!(visitor, visit_generic_param, &binder.generic_params);
-            try_visit!(visitor.visit_ty(&binder.inner_ty));
-        }
-        TyKind::Path(maybe_qself, path) => {
-            try_visit!(visitor.visit_qself(maybe_qself));
-            try_visit!(visitor.visit_path(path, *id));
-        }
-        TyKind::Pat(ty, pat) => {
-            try_visit!(visitor.visit_ty(ty));
-            try_visit!(visitor.visit_ty_pat(pat));
-        }
-        TyKind::Array(ty, length) => {
-            try_visit!(visitor.visit_ty(ty));
-            try_visit!(visitor.visit_anon_const(length));
-        }
-        TyKind::TraitObject(bounds, _syntax) => {
-            walk_list!(visitor, visit_param_bound, bounds, BoundKind::TraitObject);
-        }
-        TyKind::ImplTrait(_id, bounds) => {
-            walk_list!(visitor, visit_param_bound, bounds, BoundKind::Impl);
-        }
-        TyKind::Typeof(expression) => try_visit!(visitor.visit_anon_const(expression)),
-        TyKind::Infer | TyKind::ImplicitSelf | TyKind::Dummy => {}
-        TyKind::Err(_guar) => {}
-        TyKind::MacCall(mac) => try_visit!(visitor.visit_mac_call(mac)),
-        TyKind::Never | TyKind::CVarArgs => {}
-    }
-    V::Result::output()
-}
-
-pub fn walk_ty_pat<'a, V: Visitor<'a>>(visitor: &mut V, tp: &'a TyPat) -> V::Result {
-    let TyPat { id: _, kind, span: _, tokens: _ } = tp;
-    match kind {
-        TyPatKind::Range(start, end, _include_end) => {
-            visit_opt!(visitor, visit_anon_const, start);
-            visit_opt!(visitor, visit_anon_const, end);
-        }
-        TyPatKind::Or(variants) => walk_list!(visitor, visit_ty_pat, variants),
-        TyPatKind::Err(_) => {}
-    }
-    V::Result::output()
-}
-
-fn walk_qself<'a, V: Visitor<'a>>(visitor: &mut V, qself: &'a Option<P<QSelf>>) -> V::Result {
-    if let Some(qself) = qself {
-        let QSelf { ty, path_span: _, position: _ } = &**qself;
-        try_visit!(visitor.visit_ty(ty));
-    }
-    V::Result::output()
-}
-
-pub fn walk_path<'a, V: Visitor<'a>>(visitor: &mut V, path: &'a Path) -> V::Result {
-    let Path { span: _, segments, tokens: _ } = path;
-    walk_list!(visitor, visit_path_segment, segments);
-    V::Result::output()
-}
-
-pub fn walk_use_tree<'a, V: Visitor<'a>>(
-    visitor: &mut V,
-    use_tree: &'a UseTree,
-    id: NodeId,
-) -> V::Result {
-    let UseTree { prefix, kind, span: _ } = use_tree;
-    try_visit!(visitor.visit_path(prefix, id));
-    match kind {
-        UseTreeKind::Simple(rename) => {
-            // The extra IDs are handled during AST lowering.
-            visit_opt!(visitor, visit_ident, rename);
-        }
-        UseTreeKind::Glob => {}
-        UseTreeKind::Nested { items, span: _ } => {
-            for &(ref nested_tree, nested_id) in items {
-                try_visit!(visitor.visit_use_tree(nested_tree, nested_id, true));
+macro_rules! generate_list_visit_fns {
+    ($($name:ident, $Ty:ty, $visit_fn:ident$(, $param:ident: $ParamTy:ty)*;)+) => {
+        $(
+            fn $name<'a, V: Visitor<'a>>(
+                vis: &mut V,
+                values: &'a ThinVec<$Ty>,
+                $(
+                    $param: $ParamTy,
+                )*
+            ) -> V::Result {
+                walk_list!(vis, $visit_fn, values$(,$param)*);
+                V::Result::output()
             }
-        }
+        )+
     }
-    V::Result::output()
 }
 
-pub fn walk_path_segment<'a, V: Visitor<'a>>(
-    visitor: &mut V,
-    segment: &'a PathSegment,
+generate_list_visit_fns! {
+    visit_items, P<Item>, visit_item;
+    visit_foreign_items, P<ForeignItem>, visit_foreign_item;
+    visit_generic_params, GenericParam, visit_generic_param;
+    visit_stmts, Stmt, visit_stmt;
+    visit_pat_fields, PatField, visit_pat_field;
+    visit_variants, Variant, visit_variant;
+    visit_assoc_items, P<AssocItem>, visit_assoc_item, ctxt: AssocCtxt;
+}
+
+#[expect(rustc::pass_by_value)] // needed for symmetry with mut_visit
+fn visit_nested_use_tree<'a, V: Visitor<'a>>(
+    vis: &mut V,
+    nested_tree: &'a UseTree,
+    &nested_id: &NodeId,
 ) -> V::Result {
-    let PathSegment { ident, id: _, args } = segment;
-    try_visit!(visitor.visit_ident(ident));
-    visit_opt!(visitor, visit_generic_args, args);
-    V::Result::output()
+    vis.visit_nested_use_tree(nested_tree, nested_id)
 }
 
 pub fn walk_generic_args<'a, V>(visitor: &mut V, generic_args: &'a GenericArgs) -> V::Result
@@ -1012,52 +1171,6 @@ pub fn walk_assoc_item_constraint<'a, V: Visitor<'a>>(
     V::Result::output()
 }
 
-pub fn walk_pat<'a, V: Visitor<'a>>(visitor: &mut V, pattern: &'a Pat) -> V::Result {
-    let Pat { id, kind, span: _, tokens: _ } = pattern;
-    match kind {
-        PatKind::TupleStruct(opt_qself, path, elems) => {
-            try_visit!(visitor.visit_qself(opt_qself));
-            try_visit!(visitor.visit_path(path, *id));
-            walk_list!(visitor, visit_pat, elems);
-        }
-        PatKind::Path(opt_qself, path) => {
-            try_visit!(visitor.visit_qself(opt_qself));
-            try_visit!(visitor.visit_path(path, *id))
-        }
-        PatKind::Struct(opt_qself, path, fields, _rest) => {
-            try_visit!(visitor.visit_qself(opt_qself));
-            try_visit!(visitor.visit_path(path, *id));
-            walk_list!(visitor, visit_pat_field, fields);
-        }
-        PatKind::Box(subpattern) | PatKind::Deref(subpattern) | PatKind::Paren(subpattern) => {
-            try_visit!(visitor.visit_pat(subpattern));
-        }
-        PatKind::Ref(subpattern, _ /*mutbl*/) => {
-            try_visit!(visitor.visit_pat(subpattern));
-        }
-        PatKind::Ident(_bmode, ident, optional_subpattern) => {
-            try_visit!(visitor.visit_ident(ident));
-            visit_opt!(visitor, visit_pat, optional_subpattern);
-        }
-        PatKind::Expr(expression) => try_visit!(visitor.visit_expr(expression)),
-        PatKind::Range(lower_bound, upper_bound, _end) => {
-            visit_opt!(visitor, visit_expr, lower_bound);
-            visit_opt!(visitor, visit_expr, upper_bound);
-        }
-        PatKind::Guard(subpattern, guard_condition) => {
-            try_visit!(visitor.visit_pat(subpattern));
-            try_visit!(visitor.visit_expr(guard_condition));
-        }
-        PatKind::Missing | PatKind::Wild | PatKind::Rest | PatKind::Never => {}
-        PatKind::Err(_guar) => {}
-        PatKind::Tuple(elems) | PatKind::Slice(elems) | PatKind::Or(elems) => {
-            walk_list!(visitor, visit_pat, elems);
-        }
-        PatKind::MacCall(mac) => try_visit!(visitor.visit_mac_call(mac)),
-    }
-    V::Result::output()
-}
-
 pub fn walk_param_bound<'a, V: Visitor<'a>>(visitor: &mut V, bound: &'a GenericBound) -> V::Result {
     match bound {
         GenericBound::Trait(trait_ref) => visitor.visit_poly_trait_ref(trait_ref),
@@ -1075,7 +1188,10 @@ pub fn walk_precise_capturing_arg<'a, V: Visitor<'a>>(
 ) -> V::Result {
     match arg {
         PreciseCapturingArg::Lifetime(lt) => visitor.visit_lifetime(lt, LifetimeCtxt::GenericArg),
-        PreciseCapturingArg::Arg(path, id) => visitor.visit_path(path, *id),
+        PreciseCapturingArg::Arg(path, id) => {
+            try_visit!(visitor.visit_id(*id));
+            visitor.visit_path(path)
+        }
     }
 }
 
@@ -1216,11 +1332,9 @@ pub fn walk_fn<'a, V: Visitor<'a>>(visitor: &mut V, kind: FnKind<'a>) -> V::Resu
     V::Result::output()
 }
 
-pub fn walk_struct_def<'a, V: Visitor<'a>>(
-    visitor: &mut V,
-    struct_definition: &'a VariantData,
-) -> V::Result {
-    walk_list!(visitor, visit_field_def, struct_definition.fields());
+pub fn walk_variant_data<'a, V: Visitor<'a>>(visitor: &mut V, data: &'a VariantData) -> V::Result {
+    visit_opt!(visitor, visit_id, data.ctor_node_id());
+    walk_list!(visitor, visit_field_def, data.fields());
     V::Result::output()
 }
 
@@ -1235,12 +1349,6 @@ pub fn walk_field_def<'a, V: Visitor<'a>>(visitor: &mut V, field: &'a FieldDef)
     V::Result::output()
 }
 
-pub fn walk_block<'a, V: Visitor<'a>>(visitor: &mut V, block: &'a Block) -> V::Result {
-    let Block { stmts, id: _, rules: _, span: _, tokens: _ } = block;
-    walk_list!(visitor, visit_stmt, stmts);
-    V::Result::output()
-}
-
 pub fn walk_stmt<'a, V: Visitor<'a>>(visitor: &mut V, statement: &'a Stmt) -> V::Result {
     let Stmt { id: _, kind, span: _ } = statement;
     match kind {
@@ -1259,12 +1367,7 @@ pub fn walk_stmt<'a, V: Visitor<'a>>(visitor: &mut V, statement: &'a Stmt) -> V:
 
 pub fn walk_mac<'a, V: Visitor<'a>>(visitor: &mut V, mac: &'a MacCall) -> V::Result {
     let MacCall { path, args: _ } = mac;
-    visitor.visit_path(path, DUMMY_NODE_ID)
-}
-
-pub fn walk_anon_const<'a, V: Visitor<'a>>(visitor: &mut V, constant: &'a AnonConst) -> V::Result {
-    let AnonConst { id: _, value } = constant;
-    visitor.visit_expr(value)
+    visitor.visit_path(path)
 }
 
 pub fn walk_inline_asm<'a, V: Visitor<'a>>(visitor: &mut V, asm: &'a InlineAsm) -> V::Result {
@@ -1304,7 +1407,8 @@ pub fn walk_inline_asm_sym<'a, V: Visitor<'a>>(
     InlineAsmSym { id, qself, path }: &'a InlineAsmSym,
 ) -> V::Result {
     try_visit!(visitor.visit_qself(qself));
-    visitor.visit_path(path, *id)
+    try_visit!(visitor.visit_id(*id));
+    visitor.visit_path(path)
 }
 
 pub fn walk_format_args<'a, V: Visitor<'a>>(visitor: &mut V, fmt: &'a FormatArgs) -> V::Result {
@@ -1336,7 +1440,8 @@ pub fn walk_expr<'a, V: Visitor<'a>>(visitor: &mut V, expression: &'a Expr) -> V
         ExprKind::Struct(se) => {
             let StructExpr { qself, path, fields, rest } = &**se;
             try_visit!(visitor.visit_qself(qself));
-            try_visit!(visitor.visit_path(path, *id));
+            try_visit!(visitor.visit_id(*id));
+            try_visit!(visitor.visit_path(path));
             walk_list!(visitor, visit_expr_field, fields);
             match rest {
                 StructRest::Base(expr) => try_visit!(visitor.visit_expr(expr)),
@@ -1446,7 +1551,8 @@ pub fn walk_expr<'a, V: Visitor<'a>>(visitor: &mut V, expression: &'a Expr) -> V
         ExprKind::Underscore => {}
         ExprKind::Path(maybe_qself, path) => {
             try_visit!(visitor.visit_qself(maybe_qself));
-            try_visit!(visitor.visit_path(path, *id));
+            try_visit!(visitor.visit_id(*id));
+            try_visit!(visitor.visit_path(path));
         }
         ExprKind::Break(opt_label, opt_expr) => {
             visit_opt!(visitor, visit_label, opt_label);
@@ -1509,7 +1615,8 @@ pub fn walk_vis<'a, V: Visitor<'a>>(visitor: &mut V, vis: &'a Visibility) -> V::
     let Visibility { kind, span: _, tokens: _ } = vis;
     match kind {
         VisibilityKind::Restricted { path, id, shorthand: _ } => {
-            try_visit!(visitor.visit_path(path, *id));
+            try_visit!(visitor.visit_id(*id));
+            try_visit!(visitor.visit_path(path));
         }
         VisibilityKind::Public | VisibilityKind::Inherited => {}
     }
@@ -1522,7 +1629,7 @@ pub fn walk_attribute<'a, V: Visitor<'a>>(visitor: &mut V, attr: &'a Attribute)
         AttrKind::Normal(normal) => {
             let NormalAttr { item, tokens: _ } = &**normal;
             let AttrItem { unsafety: _, path, args, tokens: _ } = item;
-            try_visit!(visitor.visit_path(path, DUMMY_NODE_ID));
+            try_visit!(visitor.visit_path(path));
             try_visit!(walk_attr_args(visitor, args));
         }
         AttrKind::DocComment(_kind, _sym) => {}

compiler/rustc_ast_lowering/src/delegation.rs

@@ -446,13 +446,7 @@ impl<'a> SelfResolver<'a> {
 }
 
 impl<'ast, 'a> Visitor<'ast> for SelfResolver<'a> {
-    fn visit_path(&mut self, path: &'ast Path, id: NodeId) {
+    fn visit_id(&mut self, id: NodeId) {
         self.try_replace_id(id);
-        visit::walk_path(self, path);
-    }
-
-    fn visit_path_segment(&mut self, seg: &'ast PathSegment) {
-        self.try_replace_id(seg.id);
-        visit::walk_path_segment(self, seg);
     }
 }

compiler/rustc_ast_lowering/src/expr.rs

@@ -1,4 +1,3 @@
-use std::assert_matches::assert_matches;
 use std::ops::ControlFlow;
 use std::sync::Arc;
 
@@ -1199,11 +1198,13 @@ impl<'hir> LoweringContext<'_, 'hir> {
         let closure_def_id = self.local_def_id(closure_id);
         let (binder_clause, generic_params) = self.lower_closure_binder(binder);
 
-        assert_matches!(
-            coroutine_kind,
-            CoroutineKind::Async { .. },
-            "only async closures are supported currently"
-        );
+        let coroutine_desugaring = match coroutine_kind {
+            CoroutineKind::Async { .. } => hir::CoroutineDesugaring::Async,
+            CoroutineKind::Gen { .. } => hir::CoroutineDesugaring::Gen,
+            CoroutineKind::AsyncGen { span, .. } => {
+                span_bug!(span, "only async closures and `iter!` closures are supported currently")
+            }
+        };
 
         let body = self.with_new_scopes(fn_decl_span, |this| {
             let inner_decl =
@@ -1247,7 +1248,7 @@ impl<'hir> LoweringContext<'_, 'hir> {
             // Lower this as a `CoroutineClosure`. That will ensure that HIR typeck
             // knows that a `FnDecl` output type like `-> &str` actually means
             // "coroutine that returns &str", rather than directly returning a `&str`.
-            kind: hir::ClosureKind::CoroutineClosure(hir::CoroutineDesugaring::Async),
+            kind: hir::ClosureKind::CoroutineClosure(coroutine_desugaring),
             constness: hir::Constness::NotConst,
         });
         hir::ExprKind::Closure(c)

compiler/rustc_ast_lowering/src/lib.rs

@@ -732,7 +732,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
         span: Span,
         args: Option<&'hir hir::GenericArgs<'hir>>,
     ) -> &'hir hir::Path<'hir> {
-        let def_id = self.tcx.require_lang_item(lang_item, Some(span));
+        let def_id = self.tcx.require_lang_item(lang_item, span);
         let def_kind = self.tcx.def_kind(def_id);
         let res = Res::Def(def_kind, def_id);
         self.arena.alloc(hir::Path {
@@ -1406,7 +1406,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                 };
                 let span = self.tcx.sess.source_map().start_point(t.span).shrink_to_hi();
                 let region = Lifetime { ident: Ident::new(kw::UnderscoreLifetime, span), id };
-                (region, LifetimeSyntax::Hidden)
+                (region, LifetimeSyntax::Implicit)
             }
         };
         self.lower_lifetime(&region, LifetimeSource::Reference, syntax)
@@ -1790,7 +1790,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
             id,
             Ident::new(kw::UnderscoreLifetime, span),
             LifetimeSource::Path { angle_brackets },
-            LifetimeSyntax::Hidden,
+            LifetimeSyntax::Implicit,
         )
     }
 
@@ -2422,7 +2422,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
             Ident::new(kw::UnderscoreLifetime, self.lower_span(span)),
             hir::LifetimeKind::ImplicitObjectLifetimeDefault,
             LifetimeSource::Other,
-            LifetimeSyntax::Hidden,
+            LifetimeSyntax::Implicit,
         );
         debug!("elided_dyn_bound: r={:?}", r);
         self.arena.alloc(r)

compiler/rustc_ast_passes/src/feature_gate.rs

@@ -477,11 +477,12 @@ pub fn check_crate(krate: &ast::Crate, sess: &Session, features: &Features) {
         for span in spans {
             if (!visitor.features.coroutines() && !span.allows_unstable(sym::coroutines))
                 && (!visitor.features.gen_blocks() && !span.allows_unstable(sym::gen_blocks))
+                && (!visitor.features.yield_expr() && !span.allows_unstable(sym::yield_expr))
             {
                 #[allow(rustc::untranslatable_diagnostic)]
-                // Don't know which of the two features to include in the
-                // error message, so I am arbitrarily picking one.
-                feature_err(&visitor.sess, sym::coroutines, *span, "yield syntax is experimental")
+                // Emit yield_expr as the error, since that will be sufficient. You can think of it
+                // as coroutines and gen_blocks imply yield_expr.
+                feature_err(&visitor.sess, sym::yield_expr, *span, "yield syntax is experimental")
                     .emit();
             }
         }

compiler/rustc_attr_parsing/src/attributes/allow_unstable.rs

@@ -53,7 +53,7 @@ fn parse_unstable<'a>(
 
     for param in list.mixed() {
         let param_span = param.span();
-        if let Some(ident) = param.meta_item().and_then(|i| i.path_without_args().word()) {
+        if let Some(ident) = param.meta_item().and_then(|i| i.path().word()) {
             res.push(ident.name);
         } else {
             cx.emit_err(session_diagnostics::ExpectsFeatures {

compiler/rustc_attr_parsing/src/attributes/deprecation.rs

@@ -79,7 +79,7 @@ impl SingleAttributeParser for DeprecationParser {
                     return None;
                 };
 
-                let ident_name = param.path_without_args().word_sym();
+                let ident_name = param.path().word_sym();
 
                 match ident_name {
                     Some(name @ sym::since) => {
@@ -102,7 +102,7 @@ impl SingleAttributeParser for DeprecationParser {
                     _ => {
                         cx.emit_err(session_diagnostics::UnknownMetaItem {
                             span: param_span,
-                            item: param.path_without_args().to_string(),
+                            item: param.path().to_string(),
                             expected: if features.deprecated_suggestion() {
                                 &["since", "note", "suggestion"]
                             } else {

compiler/rustc_attr_parsing/src/attributes/mod.rs

@@ -74,7 +74,7 @@ pub(crate) trait AttributeParser: Default + 'static {
 pub(crate) trait SingleAttributeParser: 'static {
     const PATH: &'static [Symbol];
 
-    /// Caled when a duplicate attribute is found.
+    /// Called when a duplicate attribute is found.
     ///
     /// `first_span` is the span of the first occurrence of this attribute.
     // FIXME(jdonszelmann): default error

compiler/rustc_attr_parsing/src/attributes/repr.rs

@@ -96,7 +96,7 @@ fn parse_repr(cx: &AcceptContext<'_>, param: &MetaItemParser<'_>) -> Option<Repr
 
     // FIXME(jdonszelmann): invert the parsing here to match on the word first and then the
     // structure.
-    let (name, ident_span) = if let Some(ident) = param.path_without_args().word() {
+    let (name, ident_span) = if let Some(ident) = param.path().word() {
         (Some(ident.name), ident.span)
     } else {
         (None, DUMMY_SP)

compiler/rustc_attr_parsing/src/attributes/stability.rs

@@ -204,7 +204,7 @@ fn insert_value_into_option_or_error(
     if item.is_some() {
         cx.emit_err(session_diagnostics::MultipleItem {
             span: param.span(),
-            item: param.path_without_args().to_string(),
+            item: param.path().to_string(),
         });
         None
     } else if let Some(v) = param.args().name_value()
@@ -242,13 +242,13 @@ pub(crate) fn parse_stability(
             return None;
         };
 
-        match param.path_without_args().word_sym() {
+        match param.path().word_sym() {
             Some(sym::feature) => insert_value_into_option_or_error(cx, &param, &mut feature)?,
             Some(sym::since) => insert_value_into_option_or_error(cx, &param, &mut since)?,
             _ => {
                 cx.emit_err(session_diagnostics::UnknownMetaItem {
                     span: param_span,
-                    item: param.path_without_args().to_string(),
+                    item: param.path().to_string(),
                     expected: &["feature", "since"],
                 });
                 return None;
@@ -310,7 +310,7 @@ pub(crate) fn parse_unstability(
             return None;
         };
 
-        match param.path_without_args().word_sym() {
+        match param.path().word_sym() {
             Some(sym::feature) => insert_value_into_option_or_error(cx, &param, &mut feature)?,
             Some(sym::reason) => insert_value_into_option_or_error(cx, &param, &mut reason)?,
             Some(sym::issue) => {
@@ -349,7 +349,7 @@ pub(crate) fn parse_unstability(
             _ => {
                 cx.emit_err(session_diagnostics::UnknownMetaItem {
                     span: param.span(),
-                    item: param.path_without_args().to_string(),
+                    item: param.path().to_string(),
                     expected: &["feature", "reason", "issue", "soft", "implied_by"],
                 });
                 return None;

compiler/rustc_attr_parsing/src/context.rs

@@ -264,7 +264,8 @@ impl<'sess> AttributeParser<'sess> {
                 // }
                 ast::AttrKind::Normal(n) => {
                     let parser = MetaItemParser::from_attr(n, self.dcx());
-                    let (path, args) = parser.deconstruct();
+                    let path = parser.path();
+                    let args = parser.args();
                     let parts = path.segments().map(|i| i.name).collect::<Vec<_>>();
 
                     if let Some(accept) = ATTRIBUTE_MAPPING.0.get(parts.as_slice()) {

compiler/rustc_attr_parsing/src/lib.rs

@@ -1,31 +1,38 @@
 //! Centralized logic for parsing and attributes.
 //!
-//! Part of a series of crates:
-//! - rustc_attr_data_structures: contains types that the parsers parse into
-//! - rustc_attr_parsing: this crate
-//! - (in the future): rustc_attr_validation
+//! ## Architecture
+//! This crate is part of a series of crates that handle attribute processing.
+//! - [rustc_attr_data_structures](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_attr_data_structures/index.html): Defines the data structures that store parsed attributes
+//! - [rustc_attr_parsing](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_attr_parsing/index.html): This crate, handles the parsing of attributes
+//! - (planned) rustc_attr_validation: Will handle attribute validation
 //!
-//! History: Check out [#131229](https://github.com/rust-lang/rust/issues/131229).
-//! There used to be only one definition of attributes in the compiler: `ast::Attribute`.
-//! These were then parsed or validated or both in places distributed all over the compiler.
-//! This was a mess...
+//! The separation between data structures and parsing follows the principle of separation of concerns.
+//! Data structures (`rustc_attr_data_structures`) define what attributes look like after parsing.
+//! This crate (`rustc_attr_parsing`) handles how to convert raw tokens into those structures.
+//! This split allows other parts of the compiler to use the data structures without needing
+//! the parsing logic, making the codebase more modular and maintainable.
 //!
-//! Attributes are markers on items.
-//! Many of them are actually attribute-like proc-macros, and are expanded to some other rust syntax.
-//! This could either be a user provided proc macro, or something compiler provided.
-//! `derive` is an example of one that the compiler provides.
-//! These are built-in, but they have a valid expansion to Rust tokens and are thus called "active".
-//! I personally like calling these *active* compiler-provided attributes, built-in *macros*,
-//! because they still expand, and this helps to differentiate them from built-in *attributes*.
-//! However, I'll be the first to admit that the naming here can be confusing.
+//! ## Background
+//! Previously, the compiler had a single attribute definition (`ast::Attribute`) with parsing and
+//! validation scattered throughout the codebase. This was reorganized for better maintainability
+//! (see [#131229](https://github.com/rust-lang/rust/issues/131229)).
 //!
-//! The alternative to active attributes, are inert attributes.
-//! These can occur in user code (proc-macro helper attributes).
-//! But what's important is, many built-in attributes are inert like this.
-//! There is nothing they expand to during the macro expansion process,
-//! sometimes because they literally cannot expand to something that is valid Rust.
-//! They are really just markers to guide the compilation process.
-//! An example is `#[inline(...)]` which changes how code for functions is generated.
+//! ## Types of Attributes
+//! In Rust, attributes are markers that can be attached to items. They come in two main categories.
+//!
+//! ### 1. Active Attributes
+//! These are attribute-like proc-macros that expand into other Rust code.
+//! They can be either user-defined or compiler-provided. Examples of compiler-provided active attributes:
+//!   - `#[derive(...)]`: Expands into trait implementations
+//!   - `#[cfg()]`: Expands based on configuration
+//!   - `#[cfg_attr()]`: Conditional attribute application
+//!
+//! ### 2. Inert Attributes
+//! These are pure markers that don't expand into other code. They guide the compilation process.
+//! They can be user-defined (in proc-macro helpers) or built-in. Examples of built-in inert attributes:
+//!   - `#[stable()]`: Marks stable API items
+//!   - `#[inline()]`: Suggests function inlining
+//!   - `#[repr()]`: Controls type representation
 //!
 //! ```text
 //!                      Active                 Inert
@@ -33,27 +40,21 @@
 //!              │     (mostly in)      │    these are parsed  │
 //!              │ rustc_builtin_macros │        here!         │
 //!              │                      │                      │
-//!              │                      │                      │
 //!              │    #[derive(...)]    │    #[stable()]       │
 //!     Built-in │    #[cfg()]          │    #[inline()]       │
 //!              │    #[cfg_attr()]     │    #[repr()]         │
 //!              │                      │                      │
-//!              │                      │                      │
-//!              │                      │                      │
 //!              ├──────────────────────┼──────────────────────┤
 //!              │                      │                      │
-//!              │                      │                      │
 //!              │                      │       `b` in         │
 //!              │                      │ #[proc_macro_derive( │
 //! User created │ #[proc_macro_attr()] │    a,                │
 //!              │                      │    attributes(b)     │
 //!              │                      │ ]                    │
-//!              │                      │                      │
-//!              │                      │                      │
-//!              │                      │                      │
 //!              └──────────────────────┴──────────────────────┘
 //! ```
 //!
+//! ## How This Crate Works
 //! In this crate, syntactical attributes (sequences of tokens that look like
 //! `#[something(something else)]`) are parsed into more semantic attributes, markers on items.
 //! Multiple syntactic attributes might influence a single semantic attribute. For example,
@@ -63,18 +64,17 @@
 //! and `#[unstable()]` syntactic attributes, and at the end produce a single
 //! [`AttributeKind::Stability`](rustc_attr_data_structures::AttributeKind::Stability).
 //!
-//! As a rule of thumb, when a syntactical attribute can be applied more than once, they should be
-//! combined into a single semantic attribute. For example:
+//! When multiple instances of the same attribute are allowed, they're combined into a single
+//! semantic attribute. For example:
 //!
-//! ```
+//! ```rust
 //! #[repr(C)]
 //! #[repr(packed)]
 //! struct Meow {}
 //! ```
 //!
-//! should result in a single `AttributeKind::Repr` containing a list of repr annotations, in this
-//! case `C` and `packed`. This is equivalent to writing `#[repr(C, packed)]` in a single
-//! syntactical annotation.
+//! This is equivalent to `#[repr(C, packed)]` and results in a single `AttributeKind::Repr`
+//! containing both `C` and `packed` annotations.
 
 // tidy-alphabetical-start
 #![allow(internal_features)]

compiler/rustc_attr_parsing/src/parser.rs

@@ -252,9 +252,13 @@ impl<'a> MetaItemParser<'a> {
         }
     }
 
-    /// Gets just the path, without the args.
-    pub fn path_without_args(&self) -> PathParser<'a> {
-        self.path.clone()
+    /// Gets just the path, without the args. Some examples:
+    ///
+    /// - `#[rustfmt::skip]`: `rustfmt::skip` is a path
+    /// - `#[allow(clippy::complexity)]`: `clippy::complexity` is a path
+    /// - `#[inline]`: `inline` is a single segment path
+    pub fn path(&self) -> &PathParser<'a> {
+        &self.path
     }
 
     /// Gets just the args parser, without caring about the path.
@@ -262,50 +266,14 @@ impl<'a> MetaItemParser<'a> {
         &self.args
     }
 
-    pub fn deconstruct(&self) -> (PathParser<'a>, &ArgParser<'a>) {
-        (self.path_without_args(), self.args())
-    }
-
-    /// Asserts that this MetaItem starts with a path. Some examples:
-    ///
-    /// - `#[rustfmt::skip]`: `rustfmt::skip` is a path
-    /// - `#[allow(clippy::complexity)]`: `clippy::complexity` is a path
-    /// - `#[inline]`: `inline` is a single segment path
-    pub fn path(&self) -> (PathParser<'a>, &ArgParser<'a>) {
-        self.deconstruct()
-    }
-
-    /// Asserts that this MetaItem starts with a word, or single segment path.
-    /// Doesn't return the args parser.
-    ///
-    /// For examples. see [`Self::word`]
-    pub fn word_without_args(&self) -> Option<Ident> {
-        Some(self.word()?.0)
-    }
-
     /// Asserts that this MetaItem starts with a word, or single segment path.
     ///
     /// Some examples:
     /// - `#[inline]`: `inline` is a word
     /// - `#[rustfmt::skip]`: `rustfmt::skip` is a path,
     ///   and not a word and should instead be parsed using [`path`](Self::path)
-    pub fn word(&self) -> Option<(Ident, &ArgParser<'a>)> {
-        let (path, args) = self.deconstruct();
-        Some((path.word()?, args))
-    }
-
-    /// Asserts that this MetaItem starts with some specific word.
-    ///
-    /// See [`word`](Self::word) for examples of what a word is.
     pub fn word_is(&self, sym: Symbol) -> Option<&ArgParser<'a>> {
-        self.path_without_args().word_is(sym).then(|| self.args())
-    }
-
-    /// Asserts that this MetaItem starts with some specific path.
-    ///
-    /// See [`word`](Self::path) for examples of what a word is.
-    pub fn path_is(&self, segments: &[Symbol]) -> Option<&ArgParser<'a>> {
-        self.path_without_args().segments_is(segments).then(|| self.args())
+        self.path().word_is(sym).then(|| self.args())
     }
 }
 
@@ -548,7 +516,7 @@ impl<'a> MetaItemListParser<'a> {
     }
 
     /// Lets you pick and choose as what you want to parse each element in the list
-    pub fn mixed<'s>(&'s self) -> impl Iterator<Item = &'s MetaItemOrLitParser<'a>> + 's {
+    pub fn mixed(&self) -> impl Iterator<Item = &MetaItemOrLitParser<'a>> {
         self.sub_parsers.iter()
     }
 
@@ -560,20 +528,6 @@ impl<'a> MetaItemListParser<'a> {
         self.len() == 0
     }
 
-    /// Asserts that every item in the list is another list starting with a word.
-    ///
-    /// See [`MetaItemParser::word`] for examples of words.
-    pub fn all_word_list<'s>(&'s self) -> Option<Vec<(Ident, &'s ArgParser<'a>)>> {
-        self.mixed().map(|i| i.meta_item()?.word()).collect()
-    }
-
-    /// Asserts that every item in the list is another list starting with a full path.
-    ///
-    /// See [`MetaItemParser::path`] for examples of paths.
-    pub fn all_path_list<'s>(&'s self) -> Option<Vec<(PathParser<'a>, &'s ArgParser<'a>)>> {
-        self.mixed().map(|i| Some(i.meta_item()?.path())).collect()
-    }
-
     /// Returns Some if the list contains only a single element.
     ///
     /// Inside the Some is the parser to parse this single element.

compiler/rustc_borrowck/src/constraints/mod.rs

@@ -5,11 +5,9 @@ use rustc_index::{IndexSlice, IndexVec};
 use rustc_middle::mir::ConstraintCategory;
 use rustc_middle::ty::{RegionVid, TyCtxt, VarianceDiagInfo};
 use rustc_span::Span;
-use tracing::{debug, instrument};
+use tracing::debug;
 
-use crate::region_infer::{AnnotatedSccs, ConstraintSccs, RegionDefinition, SccAnnotations};
 use crate::type_check::Locations;
-use crate::universal_regions::UniversalRegions;
 
 pub(crate) mod graph;
 
@@ -53,112 +51,6 @@ impl<'tcx> OutlivesConstraintSet<'tcx> {
     ) -> &IndexSlice<OutlivesConstraintIndex, OutlivesConstraint<'tcx>> {
         &self.outlives
     }
-
-    /// Computes cycles (SCCs) in the graph of regions. In particular,
-    /// find all regions R1, R2 such that R1: R2 and R2: R1 and group
-    /// them into an SCC, and find the relationships between SCCs.
-    pub(crate) fn compute_sccs(
-        &self,
-        static_region: RegionVid,
-        definitions: &IndexVec<RegionVid, RegionDefinition<'tcx>>,
-    ) -> AnnotatedSccs {
-        let constraint_graph = self.graph(definitions.len());
-        let region_graph = &constraint_graph.region_graph(self, static_region);
-        let mut annotation_visitor = SccAnnotations::new(definitions);
-        (
-            ConstraintSccs::new_with_annotation(&region_graph, &mut annotation_visitor),
-            annotation_visitor.scc_to_annotation,
-        )
-    }
-
-    /// This method handles Universe errors by rewriting the constraint
-    /// graph. For each strongly connected component in the constraint
-    /// graph such that there is a series of constraints
-    ///    A: B: C: ... : X  where
-    /// A's universe is smaller than X's and A is a placeholder,
-    /// add a constraint that A: 'static. This is a safe upper bound
-    /// in the face of borrow checker/trait solver limitations that will
-    /// eventually go away.
-    ///
-    /// For a more precise definition, see the documentation for
-    /// [`crate::region_infer::RegionTracker`].
-    ///
-    /// This edge case used to be handled during constraint propagation
-    /// by iterating over the strongly connected components in the constraint
-    /// graph while maintaining a set of bookkeeping mappings similar
-    /// to what is stored in `RegionTracker` and manually adding 'static as
-    /// needed.
-    ///
-    /// It was rewritten as part of the Polonius project with the goal of moving
-    /// higher-kindedness concerns out of the path of the borrow checker,
-    /// for two reasons:
-    ///
-    /// 1. Implementing Polonius is difficult enough without also
-    ///     handling them.
-    /// 2. The long-term goal is to handle higher-kinded concerns
-    ///     in the trait solver, where they belong. This avoids
-    ///     logic duplication and allows future trait solvers
-    ///     to compute better bounds than for example our
-    ///     "must outlive 'static" here.
-    ///
-    /// This code is a stop-gap measure in preparation for the future trait solver.
-    ///
-    /// Every constraint added by this method is an
-    /// internal `IllegalUniverse` constraint.
-    #[instrument(skip(self, universal_regions, definitions))]
-    pub(crate) fn add_outlives_static(
-        &mut self,
-        universal_regions: &UniversalRegions<'tcx>,
-        definitions: &IndexVec<RegionVid, RegionDefinition<'tcx>>,
-    ) -> AnnotatedSccs {
-        let fr_static = universal_regions.fr_static;
-        let (sccs, annotations) = self.compute_sccs(fr_static, definitions);
-
-        // Changed to `true` if we added any constraints to `self` and need to
-        // recompute SCCs.
-        let mut added_constraints = false;
-
-        for scc in sccs.all_sccs() {
-            // No point in adding 'static: 'static!
-            // This micro-optimisation makes somewhat sense
-            // because static outlives *everything*.
-            if scc == sccs.scc(fr_static) {
-                continue;
-            }
-
-            let annotation = annotations[scc];
-
-            // If this SCC participates in a universe violation,
-            // e.g. if it reaches a region with a universe smaller than
-            // the largest region reached, add a requirement that it must
-            // outlive `'static`.
-            if annotation.has_incompatible_universes() {
-                // Optimisation opportunity: this will add more constraints than
-                // needed for correctness, since an SCC upstream of another with
-                // a universe violation will "infect" its downstream SCCs to also
-                // outlive static.
-                added_constraints = true;
-                let scc_representative_outlives_static = OutlivesConstraint {
-                    sup: annotation.representative,
-                    sub: fr_static,
-                    category: ConstraintCategory::IllegalUniverse,
-                    locations: Locations::All(rustc_span::DUMMY_SP),
-                    span: rustc_span::DUMMY_SP,
-                    variance_info: VarianceDiagInfo::None,
-                    from_closure: false,
-                };
-                self.push(scc_representative_outlives_static);
-            }
-        }
-
-        if added_constraints {
-            // We changed the constraint set and so must recompute SCCs.
-            self.compute_sccs(fr_static, definitions)
-        } else {
-            // If we didn't add any back-edges; no more work needs doing
-            (sccs, annotations)
-        }
-    }
 }
 
 impl<'tcx> Index<OutlivesConstraintIndex> for OutlivesConstraintSet<'tcx> {

compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs

@@ -263,7 +263,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
                 // something that already has `Fn`-like bounds (or is a closure), so we can't
                 // restrict anyways.
             } else {
-                let copy_did = self.infcx.tcx.require_lang_item(LangItem::Copy, Some(span));
+                let copy_did = self.infcx.tcx.require_lang_item(LangItem::Copy, span);
                 self.suggest_adding_bounds(&mut err, ty, copy_did, span);
             }
 
@@ -1915,7 +1915,7 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
 
         let local_ty = self.body.local_decls[place.local].ty;
         let typeck_results = tcx.typeck(self.mir_def_id());
-        let clone = tcx.require_lang_item(LangItem::Clone, Some(body.span));
+        let clone = tcx.require_lang_item(LangItem::Clone, body.span);
         for expr in expr_finder.clones {
             if let hir::ExprKind::MethodCall(_, rcvr, _, span) = expr.kind
                 && let Some(rcvr_ty) = typeck_results.node_type_opt(rcvr.hir_id)
@@ -3314,7 +3314,13 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
                     "function parameter".to_string(),
                     "function parameter borrowed here".to_string(),
                 ),
-                LocalKind::Temp if self.body.local_decls[local].is_user_variable() => {
+                LocalKind::Temp
+                    if self.body.local_decls[local].is_user_variable()
+                        && !self.body.local_decls[local]
+                            .source_info
+                            .span
+                            .in_external_macro(self.infcx.tcx.sess.source_map()) =>
+                {
                     ("local binding".to_string(), "local binding introduced here".to_string())
                 }
                 LocalKind::ReturnPointer | LocalKind::Temp => {

compiler/rustc_borrowck/src/handle_placeholders.rs

@@ -0,0 +1,348 @@
+//! Logic for lowering higher-kinded outlives constraints
+//! (with placeholders and universes) and turn them into regular
+//! outlives constraints.
+
+use rustc_data_structures::frozen::Frozen;
+use rustc_data_structures::fx::FxIndexMap;
+use rustc_data_structures::graph::scc;
+use rustc_data_structures::graph::scc::Sccs;
+use rustc_index::IndexVec;
+use rustc_infer::infer::RegionVariableOrigin;
+use rustc_middle::mir::ConstraintCategory;
+use rustc_middle::ty::{RegionVid, UniverseIndex};
+use tracing::debug;
+
+use crate::constraints::{ConstraintSccIndex, OutlivesConstraintSet};
+use crate::consumers::OutlivesConstraint;
+use crate::diagnostics::UniverseInfo;
+use crate::member_constraints::MemberConstraintSet;
+use crate::region_infer::values::{LivenessValues, PlaceholderIndices};
+use crate::region_infer::{ConstraintSccs, RegionDefinition, Representative, TypeTest};
+use crate::ty::VarianceDiagInfo;
+use crate::type_check::free_region_relations::UniversalRegionRelations;
+use crate::type_check::{Locations, MirTypeckRegionConstraints};
+use crate::universal_regions::UniversalRegions;
+use crate::{BorrowckInferCtxt, NllRegionVariableOrigin};
+
+/// A set of outlives constraints after rewriting to remove
+/// higher-kinded constraints.
+pub(crate) struct LoweredConstraints<'tcx> {
+    pub(crate) constraint_sccs: Sccs<RegionVid, ConstraintSccIndex>,
+    pub(crate) definitions: Frozen<IndexVec<RegionVid, RegionDefinition<'tcx>>>,
+    pub(crate) scc_annotations: IndexVec<ConstraintSccIndex, RegionTracker>,
+    pub(crate) member_constraints: MemberConstraintSet<'tcx, RegionVid>,
+    pub(crate) outlives_constraints: Frozen<OutlivesConstraintSet<'tcx>>,
+    pub(crate) type_tests: Vec<TypeTest<'tcx>>,
+    pub(crate) liveness_constraints: LivenessValues,
+    pub(crate) universe_causes: FxIndexMap<UniverseIndex, UniverseInfo<'tcx>>,
+    pub(crate) placeholder_indices: PlaceholderIndices,
+}
+
+impl<'d, 'tcx, A: scc::Annotation> SccAnnotations<'d, 'tcx, A> {
+    pub(crate) fn init(definitions: &'d IndexVec<RegionVid, RegionDefinition<'tcx>>) -> Self {
+        Self { scc_to_annotation: IndexVec::new(), definitions }
+    }
+}
+
+/// A Visitor for SCC annotation construction.
+pub(crate) struct SccAnnotations<'d, 'tcx, A: scc::Annotation> {
+    pub(crate) scc_to_annotation: IndexVec<ConstraintSccIndex, A>,
+    definitions: &'d IndexVec<RegionVid, RegionDefinition<'tcx>>,
+}
+
+impl scc::Annotations<RegionVid> for SccAnnotations<'_, '_, RegionTracker> {
+    fn new(&self, element: RegionVid) -> RegionTracker {
+        RegionTracker::new(element, &self.definitions[element])
+    }
+
+    fn annotate_scc(&mut self, scc: ConstraintSccIndex, annotation: RegionTracker) {
+        let idx = self.scc_to_annotation.push(annotation);
+        assert!(idx == scc);
+    }
+
+    type Ann = RegionTracker;
+    type SccIdx = ConstraintSccIndex;
+}
+
+/// An annotation for region graph SCCs that tracks
+/// the values of its elements. This annotates a single SCC.
+#[derive(Copy, Debug, Clone)]
+pub(crate) struct RegionTracker {
+    /// The largest universe of a placeholder reached from this SCC.
+    /// This includes placeholders within this SCC.
+    max_placeholder_universe_reached: UniverseIndex,
+
+    /// The largest universe nameable from this SCC.
+    /// It is the smallest nameable universes of all
+    /// existential regions reachable from it.
+    max_nameable_universe: UniverseIndex,
+
+    /// The representative Region Variable Id for this SCC.
+    pub(crate) representative: Representative,
+}
+
+impl RegionTracker {
+    pub(crate) fn new(rvid: RegionVid, definition: &RegionDefinition<'_>) -> Self {
+        let placeholder_universe =
+            if matches!(definition.origin, NllRegionVariableOrigin::Placeholder(_)) {
+                definition.universe
+            } else {
+                UniverseIndex::ROOT
+            };
+
+        Self {
+            max_placeholder_universe_reached: placeholder_universe,
+            max_nameable_universe: definition.universe,
+            representative: Representative::new(rvid, definition),
+        }
+    }
+
+    /// The largest universe this SCC can name. It's the smallest
+    /// largest nameable uninverse of any reachable region.
+    pub(crate) fn max_nameable_universe(self) -> UniverseIndex {
+        self.max_nameable_universe
+    }
+
+    fn merge_min_max_seen(&mut self, other: &Self) {
+        self.max_placeholder_universe_reached = std::cmp::max(
+            self.max_placeholder_universe_reached,
+            other.max_placeholder_universe_reached,
+        );
+
+        self.max_nameable_universe =
+            std::cmp::min(self.max_nameable_universe, other.max_nameable_universe);
+    }
+
+    /// Returns `true` if during the annotated SCC reaches a placeholder
+    /// with a universe larger than the smallest nameable universe of any
+    /// reachable existential region.
+    pub(crate) fn has_incompatible_universes(&self) -> bool {
+        self.max_nameable_universe().cannot_name(self.max_placeholder_universe_reached)
+    }
+
+    /// Determine if the tracked universes of the two SCCs are compatible.
+    pub(crate) fn universe_compatible_with(&self, other: Self) -> bool {
+        self.max_nameable_universe().can_name(other.max_nameable_universe())
+            || self.max_nameable_universe().can_name(other.max_placeholder_universe_reached)
+    }
+}
+
+impl scc::Annotation for RegionTracker {
+    fn merge_scc(mut self, other: Self) -> Self {
+        self.representative = self.representative.merge_scc(other.representative);
+        self.merge_min_max_seen(&other);
+        self
+    }
+
+    fn merge_reached(mut self, other: Self) -> Self {
+        // No update to in-component values, only add seen values.
+        self.merge_min_max_seen(&other);
+        self
+    }
+}
+
+/// Determines if the region variable definitions contain
+/// placeholders, and compute them for later use.
+fn region_definitions<'tcx>(
+    universal_regions: &UniversalRegions<'tcx>,
+    infcx: &BorrowckInferCtxt<'tcx>,
+) -> (Frozen<IndexVec<RegionVid, RegionDefinition<'tcx>>>, bool) {
+    let var_infos = infcx.get_region_var_infos();
+    // Create a RegionDefinition for each inference variable. This happens here because
+    // it allows us to sneak in a cheap check for placeholders. Otherwise, its proper home
+    // is in `RegionInferenceContext::new()`, probably.
+    let mut definitions = IndexVec::with_capacity(var_infos.len());
+    let mut has_placeholders = false;
+
+    for info in var_infos.iter() {
+        let origin = match info.origin {
+            RegionVariableOrigin::Nll(origin) => origin,
+            _ => NllRegionVariableOrigin::Existential { from_forall: false },
+        };
+
+        let definition = RegionDefinition { origin, universe: info.universe, external_name: None };
+
+        has_placeholders |= matches!(origin, NllRegionVariableOrigin::Placeholder(_));
+        definitions.push(definition);
+    }
+
+    // Add external names from universal regions in fun function definitions.
+    // FIXME: this two-step method is annoying, but I don't know how to avoid it.
+    for (external_name, variable) in universal_regions.named_universal_regions_iter() {
+        debug!("region {:?} has external name {:?}", variable, external_name);
+        definitions[variable].external_name = Some(external_name);
+    }
+    (Frozen::freeze(definitions), has_placeholders)
+}
+
+/// This method handles placeholders by rewriting the constraint
+/// graph. For each strongly connected component in the constraint
+/// graph such that there is a series of constraints
+///    A: B: C: ... : X  where
+/// A contains a placeholder whose universe cannot be named by X,
+/// add a constraint that A: 'static. This is a safe upper bound
+/// in the face of borrow checker/trait solver limitations that will
+/// eventually go away.
+///
+/// For a more precise definition, see the documentation for
+/// [`RegionTracker`] and its methods!
+///
+/// This edge case used to be handled during constraint propagation.
+/// It was rewritten as part of the Polonius project with the goal of moving
+/// higher-kindedness concerns out of the path of the borrow checker,
+/// for two reasons:
+///
+/// 1. Implementing Polonius is difficult enough without also
+///     handling them.
+/// 2. The long-term goal is to handle higher-kinded concerns
+///     in the trait solver, where they belong. This avoids
+///     logic duplication and allows future trait solvers
+///     to compute better bounds than for example our
+///     "must outlive 'static" here.
+///
+/// This code is a stop-gap measure in preparation for the future trait solver.
+///
+/// Every constraint added by this method is an internal `IllegalUniverse` constraint.
+pub(crate) fn compute_sccs_applying_placeholder_outlives_constraints<'tcx>(
+    constraints: MirTypeckRegionConstraints<'tcx>,
+    universal_region_relations: &Frozen<UniversalRegionRelations<'tcx>>,
+    infcx: &BorrowckInferCtxt<'tcx>,
+) -> LoweredConstraints<'tcx> {
+    let universal_regions = &universal_region_relations.universal_regions;
+    let (definitions, has_placeholders) = region_definitions(universal_regions, infcx);
+
+    let MirTypeckRegionConstraints {
+        placeholder_indices,
+        placeholder_index_to_region: _,
+        liveness_constraints,
+        mut outlives_constraints,
+        mut member_constraints,
+        universe_causes,
+        type_tests,
+    } = constraints;
+
+    if let Some(guar) = universal_regions.tainted_by_errors() {
+        debug!("Universal regions tainted by errors; removing constraints!");
+        // Suppress unhelpful extra errors in `infer_opaque_types` by clearing out all
+        // outlives bounds that we may end up checking.
+        outlives_constraints = Default::default();
+        member_constraints = Default::default();
+
+        // Also taint the entire scope.
+        infcx.set_tainted_by_errors(guar);
+    }
+
+    let fr_static = universal_regions.fr_static;
+    let compute_sccs =
+        |constraints: &OutlivesConstraintSet<'tcx>,
+         annotations: &mut SccAnnotations<'_, 'tcx, RegionTracker>| {
+            ConstraintSccs::new_with_annotation(
+                &constraints.graph(definitions.len()).region_graph(constraints, fr_static),
+                annotations,
+            )
+        };
+
+    let mut scc_annotations = SccAnnotations::init(&definitions);
+    let constraint_sccs = compute_sccs(&outlives_constraints, &mut scc_annotations);
+
+    // This code structure is a bit convoluted because it allows for a planned
+    // future change where the early return here has a different type of annotation
+    // that does much less work.
+    if !has_placeholders {
+        debug!("No placeholder regions found; skipping rewriting logic!");
+
+        return LoweredConstraints {
+            type_tests,
+            member_constraints,
+            constraint_sccs,
+            scc_annotations: scc_annotations.scc_to_annotation,
+            definitions,
+            outlives_constraints: Frozen::freeze(outlives_constraints),
+            liveness_constraints,
+            universe_causes,
+            placeholder_indices,
+        };
+    }
+    debug!("Placeholders present; activating placeholder handling logic!");
+
+    let added_constraints = rewrite_placeholder_outlives(
+        &constraint_sccs,
+        &scc_annotations,
+        fr_static,
+        &mut outlives_constraints,
+    );
+
+    let (constraint_sccs, scc_annotations) = if added_constraints {
+        let mut annotations = SccAnnotations::init(&definitions);
+
+        // We changed the constraint set and so must recompute SCCs.
+        // Optimisation opportunity: if we can add them incrementally (and that's
+        // possible because edges to 'static always only merge SCCs into 'static),
+        // we would potentially save a lot of work here.
+        (compute_sccs(&outlives_constraints, &mut annotations), annotations.scc_to_annotation)
+    } else {
+        // If we didn't add any back-edges; no more work needs doing
+        debug!("No constraints rewritten!");
+        (constraint_sccs, scc_annotations.scc_to_annotation)
+    };
+
+    LoweredConstraints {
+        constraint_sccs,
+        definitions,
+        scc_annotations,
+        member_constraints,
+        outlives_constraints: Frozen::freeze(outlives_constraints),
+        type_tests,
+        liveness_constraints,
+        universe_causes,
+        placeholder_indices,
+    }
+}
+
+fn rewrite_placeholder_outlives<'tcx>(
+    sccs: &Sccs<RegionVid, ConstraintSccIndex>,
+    annotations: &SccAnnotations<'_, '_, RegionTracker>,
+    fr_static: RegionVid,
+    outlives_constraints: &mut OutlivesConstraintSet<'tcx>,
+) -> bool {
+    // Changed to `true` if we added any constraints and need to
+    // recompute SCCs.
+    let mut added_constraints = false;
+
+    let annotations = &annotations.scc_to_annotation;
+
+    for scc in sccs.all_sccs() {
+        // No point in adding 'static: 'static!
+        // This micro-optimisation makes somewhat sense
+        // because static outlives *everything*.
+        if scc == sccs.scc(fr_static) {
+            continue;
+        }
+
+        let annotation = annotations[scc];
+
+        // If this SCC participates in a universe violation,
+        // e.g. if it reaches a region with a universe smaller than
+        // the largest region reached, add a requirement that it must
+        // outlive `'static`.
+        if annotation.has_incompatible_universes() {
+            // Optimisation opportunity: this will add more constraints than
+            // needed for correctness, since an SCC upstream of another with
+            // a universe violation will "infect" its downstream SCCs to also
+            // outlive static.
+            let scc_representative_outlives_static = OutlivesConstraint {
+                sup: annotation.representative.rvid(),
+                sub: fr_static,
+                category: ConstraintCategory::IllegalUniverse,
+                locations: Locations::All(rustc_span::DUMMY_SP),
+                span: rustc_span::DUMMY_SP,
+                variance_info: VarianceDiagInfo::None,
+                from_closure: false,
+            };
+            outlives_constraints.push(scc_representative_outlives_static);
+            added_constraints = true;
+            debug!("Added {:?}: 'static!", annotation.representative.rvid());
+        }
+    }
+    added_constraints
+}

compiler/rustc_borrowck/src/lib.rs

@@ -72,6 +72,7 @@ mod constraints;
 mod dataflow;
 mod def_use;
 mod diagnostics;
+mod handle_placeholders;
 mod member_constraints;
 mod nll;
 mod path_utils;

compiler/rustc_borrowck/src/nll.rs

@@ -20,6 +20,7 @@ use tracing::{debug, instrument};
 use crate::borrow_set::BorrowSet;
 use crate::consumers::ConsumerOptions;
 use crate::diagnostics::RegionErrors;
+use crate::handle_placeholders::compute_sccs_applying_placeholder_outlives_constraints;
 use crate::polonius::PoloniusDiagnosticsContext;
 use crate::polonius::legacy::{
     PoloniusFacts, PoloniusFactsExt, PoloniusLocationTable, PoloniusOutput,
@@ -113,6 +114,12 @@ pub(crate) fn compute_regions<'tcx>(
         Rc::clone(&location_map),
     );
 
+    let lowered_constraints = compute_sccs_applying_placeholder_outlives_constraints(
+        constraints,
+        &universal_region_relations,
+        infcx,
+    );
+
     // If requested, emit legacy polonius facts.
     polonius::legacy::emit_facts(
         &mut polonius_facts,
@@ -122,11 +129,15 @@ pub(crate) fn compute_regions<'tcx>(
         borrow_set,
         move_data,
         &universal_region_relations,
-        &constraints,
+        &lowered_constraints,
     );
 
-    let mut regioncx =
-        RegionInferenceContext::new(infcx, constraints, universal_region_relations, location_map);
+    let mut regioncx = RegionInferenceContext::new(
+        infcx,
+        lowered_constraints,
+        universal_region_relations,
+        location_map,
+    );
 
     // If requested for `-Zpolonius=next`, convert NLL constraints to localized outlives constraints
     // and use them to compute loan liveness.

compiler/rustc_borrowck/src/polonius/legacy/mod.rs

@@ -13,7 +13,7 @@ use tracing::debug;
 
 use crate::borrow_set::BorrowSet;
 use crate::constraints::OutlivesConstraint;
-use crate::type_check::MirTypeckRegionConstraints;
+use crate::handle_placeholders::LoweredConstraints;
 use crate::type_check::free_region_relations::UniversalRegionRelations;
 use crate::universal_regions::UniversalRegions;
 
@@ -43,7 +43,7 @@ pub(crate) fn emit_facts<'tcx>(
     borrow_set: &BorrowSet<'tcx>,
     move_data: &MoveData<'tcx>,
     universal_region_relations: &UniversalRegionRelations<'tcx>,
-    constraints: &MirTypeckRegionConstraints<'tcx>,
+    constraints: &LoweredConstraints<'tcx>,
 ) {
     let Some(facts) = facts else {
         // We don't do anything if there are no facts to fill.
@@ -203,7 +203,7 @@ pub(crate) fn emit_drop_facts<'tcx>(
 fn emit_outlives_facts<'tcx>(
     facts: &mut PoloniusFacts,
     location_table: &PoloniusLocationTable,
-    constraints: &MirTypeckRegionConstraints<'tcx>,
+    constraints: &LoweredConstraints<'tcx>,
 ) {
     facts.subset_base.extend(constraints.outlives_constraints.outlives().iter().flat_map(
         |constraint: &OutlivesConstraint<'_>| {

compiler/rustc_borrowck/src/region_infer/dump_mir.rs

@@ -46,7 +46,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
                 "| {r:rw$?} | {ui:4?} | {v}",
                 r = region,
                 rw = REGION_WIDTH,
-                ui = self.region_universe(region),
+                ui = self.max_nameable_universe(self.constraint_sccs.scc(region)),
                 v = self.region_value_str(region),
             )?;
         }

compiler/rustc_borrowck/src/region_infer/mod.rs

@@ -11,7 +11,7 @@ use rustc_hir::def_id::CRATE_DEF_ID;
 use rustc_index::IndexVec;
 use rustc_infer::infer::outlives::test_type_match;
 use rustc_infer::infer::region_constraints::{GenericKind, VerifyBound, VerifyIfEq};
-use rustc_infer::infer::{InferCtxt, NllRegionVariableOrigin, RegionVariableOrigin};
+use rustc_infer::infer::{InferCtxt, NllRegionVariableOrigin};
 use rustc_middle::bug;
 use rustc_middle::mir::{
     AnnotationSource, BasicBlock, Body, ConstraintCategory, Local, Location, ReturnConstraint,
@@ -28,13 +28,14 @@ use crate::constraints::graph::{self, NormalConstraintGraph, RegionGraph};
 use crate::constraints::{ConstraintSccIndex, OutlivesConstraint, OutlivesConstraintSet};
 use crate::dataflow::BorrowIndex;
 use crate::diagnostics::{RegionErrorKind, RegionErrors, UniverseInfo};
+use crate::handle_placeholders::{LoweredConstraints, RegionTracker};
 use crate::member_constraints::{MemberConstraintSet, NllMemberConstraintIndex};
 use crate::polonius::LiveLoans;
 use crate::polonius::legacy::PoloniusOutput;
 use crate::region_infer::reverse_sccs::ReverseSccGraph;
 use crate::region_infer::values::{LivenessValues, RegionElement, RegionValues, ToElementIndex};
+use crate::type_check::Locations;
 use crate::type_check::free_region_relations::UniversalRegionRelations;
-use crate::type_check::{Locations, MirTypeckRegionConstraints};
 use crate::universal_regions::UniversalRegions;
 use crate::{
     BorrowckInferCtxt, ClosureOutlivesRequirement, ClosureOutlivesSubject,
@@ -48,125 +49,48 @@ mod reverse_sccs;
 
 pub(crate) mod values;
 
-pub(crate) type ConstraintSccs = Sccs<RegionVid, ConstraintSccIndex>;
-pub(crate) type AnnotatedSccs = (ConstraintSccs, IndexVec<ConstraintSccIndex, RegionTracker>);
-
-/// An annotation for region graph SCCs that tracks
-/// the values of its elements. This annotates a single SCC.
-#[derive(Copy, Debug, Clone)]
-pub(crate) struct RegionTracker {
-    /// The largest universe of a placeholder reached from this SCC.
-    /// This includes placeholders within this SCC.
-    max_placeholder_universe_reached: UniverseIndex,
-
-    /// The smallest universe index reachable form the nodes of this SCC.
-    min_reachable_universe: UniverseIndex,
-
-    /// The representative Region Variable Id for this SCC. We prefer
-    /// placeholders over existentially quantified variables, otherwise
-    ///  it's the one with the smallest Region Variable ID.
-    pub(crate) representative: RegionVid,
-
-    /// Is the current representative a placeholder?
-    representative_is_placeholder: bool,
-
-    /// Is the current representative existentially quantified?
-    representative_is_existential: bool,
+/// The representative region variable for an SCC, tagged by its origin.
+/// We prefer placeholders over existentially quantified variables, otherwise
+/// it's the one with the smallest Region Variable ID. In other words,
+/// the order of this enumeration really matters!
+#[derive(Copy, Debug, Clone, PartialEq, PartialOrd, Eq, Ord)]
+pub(crate) enum Representative {
+    FreeRegion(RegionVid),
+    Placeholder(RegionVid),
+    Existential(RegionVid),
 }
 
-impl scc::Annotation for RegionTracker {
-    fn merge_scc(mut self, mut other: Self) -> Self {
-        // Prefer any placeholder over any existential
-        if other.representative_is_placeholder && self.representative_is_existential {
-            other.merge_min_max_seen(&self);
-            return other;
+impl Representative {
+    pub(crate) fn rvid(self) -> RegionVid {
+        match self {
+            Representative::FreeRegion(region_vid)
+            | Representative::Placeholder(region_vid)
+            | Representative::Existential(region_vid) => region_vid,
         }
-
-        if self.representative_is_placeholder && other.representative_is_existential
-            || (self.representative <= other.representative)
-        {
-            self.merge_min_max_seen(&other);
-            return self;
-        }
-        other.merge_min_max_seen(&self);
-        other
     }
 
-    fn merge_reached(mut self, other: Self) -> Self {
-        // No update to in-component values, only add seen values.
-        self.merge_min_max_seen(&other);
+    pub(crate) fn new(r: RegionVid, definition: &RegionDefinition<'_>) -> Self {
+        match definition.origin {
+            NllRegionVariableOrigin::FreeRegion => Representative::FreeRegion(r),
+            NllRegionVariableOrigin::Placeholder(_) => Representative::Placeholder(r),
+            NllRegionVariableOrigin::Existential { .. } => Representative::Existential(r),
+        }
+    }
+}
+
+impl scc::Annotation for Representative {
+    fn merge_scc(self, other: Self) -> Self {
+        // Just pick the smallest one. Note that we order by tag first!
+        std::cmp::min(self, other)
+    }
+
+    // For reachability, we do nothing since the representative doesn't change.
+    fn merge_reached(self, _other: Self) -> Self {
         self
     }
 }
 
-/// A Visitor for SCC annotation construction.
-pub(crate) struct SccAnnotations<'d, 'tcx, A: scc::Annotation> {
-    pub(crate) scc_to_annotation: IndexVec<ConstraintSccIndex, A>,
-    definitions: &'d IndexVec<RegionVid, RegionDefinition<'tcx>>,
-}
-
-impl<'d, 'tcx, A: scc::Annotation> SccAnnotations<'d, 'tcx, A> {
-    pub(crate) fn new(definitions: &'d IndexVec<RegionVid, RegionDefinition<'tcx>>) -> Self {
-        Self { scc_to_annotation: IndexVec::new(), definitions }
-    }
-}
-
-impl scc::Annotations<RegionVid> for SccAnnotations<'_, '_, RegionTracker> {
-    fn new(&self, element: RegionVid) -> RegionTracker {
-        RegionTracker::new(element, &self.definitions[element])
-    }
-
-    fn annotate_scc(&mut self, scc: ConstraintSccIndex, annotation: RegionTracker) {
-        let idx = self.scc_to_annotation.push(annotation);
-        assert!(idx == scc);
-    }
-
-    type Ann = RegionTracker;
-    type SccIdx = ConstraintSccIndex;
-}
-
-impl RegionTracker {
-    pub(crate) fn new(rvid: RegionVid, definition: &RegionDefinition<'_>) -> Self {
-        let (representative_is_placeholder, representative_is_existential) = match definition.origin
-        {
-            NllRegionVariableOrigin::FreeRegion => (false, false),
-            NllRegionVariableOrigin::Placeholder(_) => (true, false),
-            NllRegionVariableOrigin::Existential { .. } => (false, true),
-        };
-
-        let placeholder_universe =
-            if representative_is_placeholder { definition.universe } else { UniverseIndex::ROOT };
-
-        Self {
-            max_placeholder_universe_reached: placeholder_universe,
-            min_reachable_universe: definition.universe,
-            representative: rvid,
-            representative_is_placeholder,
-            representative_is_existential,
-        }
-    }
-
-    /// The smallest-indexed universe reachable from and/or in this SCC.
-    fn min_universe(self) -> UniverseIndex {
-        self.min_reachable_universe
-    }
-
-    fn merge_min_max_seen(&mut self, other: &Self) {
-        self.max_placeholder_universe_reached = std::cmp::max(
-            self.max_placeholder_universe_reached,
-            other.max_placeholder_universe_reached,
-        );
-
-        self.min_reachable_universe =
-            std::cmp::min(self.min_reachable_universe, other.min_reachable_universe);
-    }
-
-    /// Returns `true` if during the annotated SCC reaches a placeholder
-    /// with a universe larger than the smallest reachable one, `false` otherwise.
-    pub(crate) fn has_incompatible_universes(&self) -> bool {
-        self.min_universe().cannot_name(self.max_placeholder_universe_reached)
-    }
-}
+pub(crate) type ConstraintSccs = Sccs<RegionVid, ConstraintSccIndex>;
 
 pub struct RegionInferenceContext<'tcx> {
     /// Contains the definition for every region variable. Region
@@ -414,26 +338,6 @@ fn sccs_info<'tcx>(infcx: &BorrowckInferCtxt<'tcx>, sccs: &ConstraintSccs) {
     debug!("SCC edges {:#?}", scc_node_to_edges);
 }
 
-fn create_definitions<'tcx>(
-    infcx: &BorrowckInferCtxt<'tcx>,
-    universal_regions: &UniversalRegions<'tcx>,
-) -> Frozen<IndexVec<RegionVid, RegionDefinition<'tcx>>> {
-    // Create a RegionDefinition for each inference variable.
-    let mut definitions: IndexVec<_, _> = infcx
-        .get_region_var_infos()
-        .iter()
-        .map(|info| RegionDefinition::new(info.universe, info.origin))
-        .collect();
-
-    // Add the external name for all universal regions.
-    for (external_name, variable) in universal_regions.named_universal_regions_iter() {
-        debug!("region {variable:?} has external name {external_name:?}");
-        definitions[variable].external_name = Some(external_name);
-    }
-
-    Frozen::freeze(definitions)
-}
-
 impl<'tcx> RegionInferenceContext<'tcx> {
     /// Creates a new region inference context with a total of
     /// `num_region_variables` valid inference variables; the first N
@@ -444,42 +348,30 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     /// of constraints produced by the MIR type check.
     pub(crate) fn new(
         infcx: &BorrowckInferCtxt<'tcx>,
-        constraints: MirTypeckRegionConstraints<'tcx>,
+        lowered_constraints: LoweredConstraints<'tcx>,
         universal_region_relations: Frozen<UniversalRegionRelations<'tcx>>,
         location_map: Rc<DenseLocationMap>,
     ) -> Self {
         let universal_regions = &universal_region_relations.universal_regions;
-        let MirTypeckRegionConstraints {
-            placeholder_indices,
-            placeholder_index_to_region: _,
-            liveness_constraints,
-            mut outlives_constraints,
-            mut member_constraints,
-            universe_causes,
+
+        let LoweredConstraints {
+            constraint_sccs,
+            definitions,
+            outlives_constraints,
+            scc_annotations,
             type_tests,
-        } = constraints;
+            liveness_constraints,
+            universe_causes,
+            placeholder_indices,
+            member_constraints,
+        } = lowered_constraints;
 
         debug!("universal_regions: {:#?}", universal_region_relations.universal_regions);
         debug!("outlives constraints: {:#?}", outlives_constraints);
         debug!("placeholder_indices: {:#?}", placeholder_indices);
         debug!("type tests: {:#?}", type_tests);
 
-        if let Some(guar) = universal_region_relations.universal_regions.tainted_by_errors() {
-            // Suppress unhelpful extra errors in `infer_opaque_types` by clearing out all
-            // outlives bounds that we may end up checking.
-            outlives_constraints = Default::default();
-            member_constraints = Default::default();
-
-            // Also taint the entire scope.
-            infcx.set_tainted_by_errors(guar);
-        }
-
-        let definitions = create_definitions(infcx, &universal_regions);
-
-        let (constraint_sccs, scc_annotations) =
-            outlives_constraints.add_outlives_static(&universal_regions, &definitions);
-        let constraints = Frozen::freeze(outlives_constraints);
-        let constraint_graph = Frozen::freeze(constraints.graph(definitions.len()));
+        let constraint_graph = Frozen::freeze(outlives_constraints.graph(definitions.len()));
 
         if cfg!(debug_assertions) {
             sccs_info(infcx, &constraint_sccs);
@@ -499,7 +391,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         let mut result = Self {
             definitions,
             liveness_constraints,
-            constraints,
+            constraints: outlives_constraints,
             constraint_graph,
             constraint_sccs,
             scc_annotations,
@@ -658,11 +550,6 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         self.scc_values.placeholders_contained_in(scc)
     }
 
-    /// Returns access to the value of `r` for debugging purposes.
-    pub(crate) fn region_universe(&self, r: RegionVid) -> ty::UniverseIndex {
-        self.scc_universe(self.constraint_sccs.scc(r))
-    }
-
     /// Once region solving has completed, this function will return the member constraints that
     /// were applied to the value of a given SCC `scc`. See `AppliedMemberConstraint`.
     pub(crate) fn applied_member_constraints(
@@ -826,7 +713,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
 
         // If the member region lives in a higher universe, we currently choose
         // the most conservative option by leaving it unchanged.
-        if !self.scc_universe(scc).is_root() {
+        if !self.max_nameable_universe(scc).is_root() {
             return;
         }
 
@@ -902,20 +789,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     /// in `scc_a`. Used during constraint propagation, and only once
     /// the value of `scc_b` has been computed.
     fn universe_compatible(&self, scc_b: ConstraintSccIndex, scc_a: ConstraintSccIndex) -> bool {
-        let a_annotation = self.scc_annotations[scc_a];
-        let b_annotation = self.scc_annotations[scc_b];
-        let a_universe = a_annotation.min_universe();
-
-        // If scc_b's declared universe is a subset of
-        // scc_a's declared universe (typically, both are ROOT), then
-        // it cannot contain any problematic universe elements.
-        if a_universe.can_name(b_annotation.min_universe()) {
-            return true;
-        }
-
-        // Otherwise, there can be no placeholder in `b` with a too high
-        // universe index to name from `a`.
-        a_universe.can_name(b_annotation.max_placeholder_universe_reached)
+        self.scc_annotations[scc_a].universe_compatible_with(self.scc_annotations[scc_b])
     }
 
     /// Once regions have been propagated, this method is used to see
@@ -1019,7 +893,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
             "lower_bound = {:?} r_scc={:?} universe={:?}",
             lower_bound,
             r_scc,
-            self.scc_universe(r_scc)
+            self.max_nameable_universe(r_scc)
         );
         // If the type test requires that `T: 'a` where `'a` is a
         // placeholder from another universe, that effectively requires
@@ -1497,10 +1371,9 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         }
     }
 
-    /// The minimum universe of any variable reachable from this
-    /// SCC, inside or outside of it.
-    fn scc_universe(&self, scc: ConstraintSccIndex) -> UniverseIndex {
-        self.scc_annotations[scc].min_universe()
+    /// The largest universe of any region nameable from this SCC.
+    fn max_nameable_universe(&self, scc: ConstraintSccIndex) -> UniverseIndex {
+        self.scc_annotations[scc].max_nameable_universe()
     }
 
     /// Checks the final value for the free region `fr` to see if it
@@ -1522,7 +1395,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
 
         // Because this free region must be in the ROOT universe, we
         // know it cannot contain any bound universes.
-        assert!(self.scc_universe(longer_fr_scc).is_root());
+        assert!(self.max_nameable_universe(longer_fr_scc).is_root());
 
         // Only check all of the relations for the main representative of each
         // SCC, otherwise just check that we outlive said representative. This
@@ -1913,7 +1786,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     #[instrument(skip(self), level = "trace", ret)]
     pub(crate) fn find_sub_region_live_at(&self, fr1: RegionVid, location: Location) -> RegionVid {
         trace!(scc = ?self.constraint_sccs.scc(fr1));
-        trace!(universe = ?self.region_universe(fr1));
+        trace!(universe = ?self.max_nameable_universe(self.constraint_sccs.scc(fr1)));
         self.find_constraint_paths_between_regions(fr1, |r| {
             // First look for some `r` such that `fr1: r` and `r` is live at `location`
             trace!(?r, liveness_constraints=?self.liveness_constraints.pretty_print_live_points(r));
@@ -2244,7 +2117,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     /// they *must* be equal (though not having the same repr does not
     /// mean they are unequal).
     fn scc_representative(&self, scc: ConstraintSccIndex) -> RegionVid {
-        self.scc_annotations[scc].representative
+        self.scc_annotations[scc].representative.rvid()
     }
 
     pub(crate) fn liveness_constraints(&self) -> &LivenessValues {
@@ -2266,21 +2139,6 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     }
 }
 
-impl<'tcx> RegionDefinition<'tcx> {
-    fn new(universe: ty::UniverseIndex, rv_origin: RegionVariableOrigin) -> Self {
-        // Create a new region definition. Note that, for free
-        // regions, the `external_name` field gets updated later in
-        // `init_free_and_bound_regions`.
-
-        let origin = match rv_origin {
-            RegionVariableOrigin::Nll(origin) => origin,
-            _ => NllRegionVariableOrigin::Existential { from_forall: false },
-        };
-
-        Self { origin, universe, external_name: None }
-    }
-}
-
 #[derive(Clone, Debug)]
 pub(crate) struct BlameConstraint<'tcx> {
     pub category: ConstraintCategory<'tcx>,

compiler/rustc_borrowck/src/region_infer/opaque_types.rs

@@ -191,7 +191,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
                 let scc = self.constraint_sccs.scc(vid);
 
                 // Special handling of higher-ranked regions.
-                if !self.scc_universe(scc).is_root() {
+                if !self.max_nameable_universe(scc).is_root() {
                     match self.scc_values.placeholders_contained_in(scc).enumerate().last() {
                         // If the region contains a single placeholder then they're equal.
                         Some((0, placeholder)) => {

compiler/rustc_borrowck/src/type_check/input_output.rs

@@ -52,7 +52,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
             assert_matches!(
                 self.tcx().coroutine_kind(self.tcx().coroutine_for_closure(mir_def_id)),
                 Some(hir::CoroutineKind::Desugared(
-                    hir::CoroutineDesugaring::Async,
+                    hir::CoroutineDesugaring::Async | hir::CoroutineDesugaring::Gen,
                     hir::CoroutineSource::Closure
                 )),
                 "this needs to be modified if we're lowering non-async closures"

compiler/rustc_borrowck/src/type_check/mod.rs

@@ -688,7 +688,7 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
                 if !self.unsized_feature_enabled() {
                     let trait_ref = ty::TraitRef::new(
                         tcx,
-                        tcx.require_lang_item(LangItem::Sized, Some(self.last_span)),
+                        tcx.require_lang_item(LangItem::Sized, self.last_span),
                         [place_ty],
                     );
                     self.prove_trait_ref(
@@ -1010,7 +1010,7 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
                             let ty = place.ty(self.body, tcx).ty;
                             let trait_ref = ty::TraitRef::new(
                                 tcx,
-                                tcx.require_lang_item(LangItem::Copy, Some(span)),
+                                tcx.require_lang_item(LangItem::Copy, span),
                                 [ty],
                             );
 
@@ -1025,11 +1025,8 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
             }
 
             &Rvalue::NullaryOp(NullOp::SizeOf | NullOp::AlignOf, ty) => {
-                let trait_ref = ty::TraitRef::new(
-                    tcx,
-                    tcx.require_lang_item(LangItem::Sized, Some(span)),
-                    [ty],
-                );
+                let trait_ref =
+                    ty::TraitRef::new(tcx, tcx.require_lang_item(LangItem::Sized, span), [ty]);
 
                 self.prove_trait_ref(
                     trait_ref,
@@ -1041,11 +1038,8 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
             &Rvalue::NullaryOp(NullOp::UbChecks, _) => {}
 
             Rvalue::ShallowInitBox(_operand, ty) => {
-                let trait_ref = ty::TraitRef::new(
-                    tcx,
-                    tcx.require_lang_item(LangItem::Sized, Some(span)),
-                    [*ty],
-                );
+                let trait_ref =
+                    ty::TraitRef::new(tcx, tcx.require_lang_item(LangItem::Sized, span), [*ty]);
 
                 self.prove_trait_ref(
                     trait_ref,
@@ -1222,7 +1216,7 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
                         let &ty = ty;
                         let trait_ref = ty::TraitRef::new(
                             tcx,
-                            tcx.require_lang_item(LangItem::CoerceUnsized, Some(span)),
+                            tcx.require_lang_item(LangItem::CoerceUnsized, span),
                             [op.ty(self.body, tcx), ty],
                         );
 
@@ -1811,7 +1805,7 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> {
         if let PlaceContext::NonMutatingUse(NonMutatingUseContext::Copy) = context {
             let trait_ref = ty::TraitRef::new(
                 tcx,
-                tcx.require_lang_item(LangItem::Copy, Some(self.last_span)),
+                tcx.require_lang_item(LangItem::Copy, self.last_span),
                 [place_ty.ty],
             );
 

compiler/rustc_borrowck/src/universal_regions.rs

@@ -544,10 +544,10 @@ impl<'cx, 'tcx> UniversalRegionsBuilder<'cx, 'tcx> {
         // (as it's created inside the body itself, not passed in from outside).
         if let DefiningTy::FnDef(def_id, _) = defining_ty {
             if self.infcx.tcx.fn_sig(def_id).skip_binder().c_variadic() {
-                let va_list_did = self.infcx.tcx.require_lang_item(
-                    LangItem::VaList,
-                    Some(self.infcx.tcx.def_span(self.mir_def)),
-                );
+                let va_list_did = self
+                    .infcx
+                    .tcx
+                    .require_lang_item(LangItem::VaList, self.infcx.tcx.def_span(self.mir_def));
 
                 let reg_vid = self
                     .infcx

compiler/rustc_builtin_macros/src/deriving/cmp/partial_eq.rs

@@ -8,6 +8,8 @@ use crate::deriving::generic::ty::*;
 use crate::deriving::generic::*;
 use crate::deriving::{path_local, path_std};
 
+/// Expands a `#[derive(PartialEq)]` attribute into an implementation for the
+/// target item.
 pub(crate) fn expand_deriving_partial_eq(
     cx: &ExtCtxt<'_>,
     span: Span,
@@ -16,62 +18,6 @@ pub(crate) fn expand_deriving_partial_eq(
     push: &mut dyn FnMut(Annotatable),
     is_const: bool,
 ) {
-    fn cs_eq(cx: &ExtCtxt<'_>, span: Span, substr: &Substructure<'_>) -> BlockOrExpr {
-        let base = true;
-        let expr = cs_fold(
-            true, // use foldl
-            cx,
-            span,
-            substr,
-            |cx, fold| match fold {
-                CsFold::Single(field) => {
-                    let [other_expr] = &field.other_selflike_exprs[..] else {
-                        cx.dcx()
-                            .span_bug(field.span, "not exactly 2 arguments in `derive(PartialEq)`");
-                    };
-
-                    // We received arguments of type `&T`. Convert them to type `T` by stripping
-                    // any leading `&`. This isn't necessary for type checking, but
-                    // it results in better error messages if something goes wrong.
-                    //
-                    // Note: for arguments that look like `&{ x }`, which occur with packed
-                    // structs, this would cause expressions like `{ self.x } == { other.x }`,
-                    // which isn't valid Rust syntax. This wouldn't break compilation because these
-                    // AST nodes are constructed within the compiler. But it would mean that code
-                    // printed by `-Zunpretty=expanded` (or `cargo expand`) would have invalid
-                    // syntax, which would be suboptimal. So we wrap these in parens, giving
-                    // `({ self.x }) == ({ other.x })`, which is valid syntax.
-                    let convert = |expr: &P<Expr>| {
-                        if let ExprKind::AddrOf(BorrowKind::Ref, Mutability::Not, inner) =
-                            &expr.kind
-                        {
-                            if let ExprKind::Block(..) = &inner.kind {
-                                // `&{ x }` form: remove the `&`, add parens.
-                                cx.expr_paren(field.span, inner.clone())
-                            } else {
-                                // `&x` form: remove the `&`.
-                                inner.clone()
-                            }
-                        } else {
-                            expr.clone()
-                        }
-                    };
-                    cx.expr_binary(
-                        field.span,
-                        BinOpKind::Eq,
-                        convert(&field.self_expr),
-                        convert(other_expr),
-                    )
-                }
-                CsFold::Combine(span, expr1, expr2) => {
-                    cx.expr_binary(span, BinOpKind::And, expr1, expr2)
-                }
-                CsFold::Fieldless => cx.expr_bool(span, base),
-            },
-        );
-        BlockOrExpr::new_expr(expr)
-    }
-
     let structural_trait_def = TraitDef {
         span,
         path: path_std!(marker::StructuralPartialEq),
@@ -97,7 +43,9 @@ pub(crate) fn expand_deriving_partial_eq(
         ret_ty: Path(path_local!(bool)),
         attributes: thin_vec![cx.attr_word(sym::inline, span)],
         fieldless_variants_strategy: FieldlessVariantsStrategy::Unify,
-        combine_substructure: combine_substructure(Box::new(|a, b, c| cs_eq(a, b, c))),
+        combine_substructure: combine_substructure(Box::new(|a, b, c| {
+            BlockOrExpr::new_expr(get_substructure_equality_expr(a, b, c))
+        })),
     }];
 
     let trait_def = TraitDef {
@@ -113,3 +61,156 @@ pub(crate) fn expand_deriving_partial_eq(
     };
     trait_def.expand(cx, mitem, item, push)
 }
+
+/// Generates the equality expression for a struct or enum variant when deriving
+/// `PartialEq`.
+///
+/// This function generates an expression that checks if all fields of a struct
+/// or enum variant are equal.
+/// - Scalar fields are compared first for efficiency, followed by compound
+///   fields.
+/// - If there are no fields, returns `true` (fieldless types are always equal).
+///
+/// Whether a field is considered "scalar" is determined by comparing the symbol
+/// of its type to a set of known scalar type symbols (e.g., `i32`, `u8`, etc).
+/// This check is based on the type's symbol.
+///
+/// ### Example 1
+/// ```
+/// #[derive(PartialEq)]
+/// struct i32;
+///
+/// // Here, `field_2` is of type `i32`, but since it's a user-defined type (not
+/// // the primitive), it will not be treated as scalar. The function will still
+/// // check equality of `field_2` first because the symbol matches `i32`.
+/// #[derive(PartialEq)]
+/// struct Struct {
+///     field_1: &'static str,
+///     field_2: i32,
+/// }
+/// ```
+///
+/// ### Example 2
+/// ```
+/// mod ty {
+///     pub type i32 = i32;
+/// }
+///
+/// // Here, `field_2` is of type `ty::i32`, which is a type alias for `i32`.
+/// // However, the function will not reorder the fields because the symbol for
+/// // `ty::i32` does not match the symbol for the primitive `i32`
+/// // ("ty::i32" != "i32").
+/// #[derive(PartialEq)]
+/// struct Struct {
+///     field_1: &'static str,
+///     field_2: ty::i32,
+/// }
+/// ```
+///
+/// For enums, the discriminant is compared first, then the rest of the fields.
+///
+/// # Panics
+///
+/// If called on static or all-fieldless enums/structs, which should not occur
+/// during derive expansion.
+fn get_substructure_equality_expr(
+    cx: &ExtCtxt<'_>,
+    span: Span,
+    substructure: &Substructure<'_>,
+) -> P<Expr> {
+    use SubstructureFields::*;
+
+    match substructure.fields {
+        EnumMatching(.., fields) | Struct(.., fields) => {
+            let combine = move |acc, field| {
+                let rhs = get_field_equality_expr(cx, field);
+                if let Some(lhs) = acc {
+                    // Combine the previous comparison with the current field
+                    // using logical AND.
+                    return Some(cx.expr_binary(field.span, BinOpKind::And, lhs, rhs));
+                }
+                // Start the chain with the first field's comparison.
+                Some(rhs)
+            };
+
+            // First compare scalar fields, then compound fields, combining all
+            // with logical AND.
+            return fields
+                .iter()
+                .filter(|field| !field.maybe_scalar)
+                .fold(fields.iter().filter(|field| field.maybe_scalar).fold(None, combine), combine)
+                // If there are no fields, treat as always equal.
+                .unwrap_or_else(|| cx.expr_bool(span, true));
+        }
+        EnumDiscr(disc, match_expr) => {
+            let lhs = get_field_equality_expr(cx, disc);
+            let Some(match_expr) = match_expr else {
+                return lhs;
+            };
+            // Compare the discriminant first (cheaper), then the rest of the
+            // fields.
+            return cx.expr_binary(disc.span, BinOpKind::And, lhs, match_expr.clone());
+        }
+        StaticEnum(..) => cx.dcx().span_bug(
+            span,
+            "unexpected static enum encountered during `derive(PartialEq)` expansion",
+        ),
+        StaticStruct(..) => cx.dcx().span_bug(
+            span,
+            "unexpected static struct encountered during `derive(PartialEq)` expansion",
+        ),
+        AllFieldlessEnum(..) => cx.dcx().span_bug(
+            span,
+            "unexpected all-fieldless enum encountered during `derive(PartialEq)` expansion",
+        ),
+    }
+}
+
+/// Generates an equality comparison expression for a single struct or enum
+/// field.
+///
+/// This function produces an AST expression that compares the `self` and
+/// `other` values for a field using `==`. It removes any leading references
+/// from both sides for readability. If the field is a block expression, it is
+/// wrapped in parentheses to ensure valid syntax.
+///
+/// # Panics
+///
+/// Panics if there are not exactly two arguments to compare (should be `self`
+/// and `other`).
+fn get_field_equality_expr(cx: &ExtCtxt<'_>, field: &FieldInfo) -> P<Expr> {
+    let [rhs] = &field.other_selflike_exprs[..] else {
+        cx.dcx().span_bug(field.span, "not exactly 2 arguments in `derive(PartialEq)`");
+    };
+
+    cx.expr_binary(
+        field.span,
+        BinOpKind::Eq,
+        wrap_block_expr(cx, peel_refs(&field.self_expr)),
+        wrap_block_expr(cx, peel_refs(rhs)),
+    )
+}
+
+/// Removes all leading immutable references from an expression.
+///
+/// This is used to strip away any number of leading `&` from an expression
+/// (e.g., `&&&T` becomes `T`). Only removes immutable references; mutable
+/// references are preserved.
+fn peel_refs(mut expr: &P<Expr>) -> P<Expr> {
+    while let ExprKind::AddrOf(BorrowKind::Ref, Mutability::Not, inner) = &expr.kind {
+        expr = &inner;
+    }
+    expr.clone()
+}
+
+/// Wraps a block expression in parentheses to ensure valid AST in macro
+/// expansion output.
+///
+/// If the given expression is a block, it is wrapped in parentheses; otherwise,
+/// it is returned unchanged.
+fn wrap_block_expr(cx: &ExtCtxt<'_>, expr: P<Expr>) -> P<Expr> {
+    if matches!(&expr.kind, ExprKind::Block(..)) {
+        return cx.expr_paren(expr.span, expr);
+    }
+    expr
+}

compiler/rustc_builtin_macros/src/deriving/generic/mod.rs

@@ -284,6 +284,7 @@ pub(crate) struct FieldInfo {
     /// The expressions corresponding to references to this field in
     /// the other selflike arguments.
     pub other_selflike_exprs: Vec<P<Expr>>,
+    pub maybe_scalar: bool,
 }
 
 #[derive(Copy, Clone)]
@@ -1220,7 +1221,8 @@ impl<'a> MethodDef<'a> {
 
             let self_expr = discr_exprs.remove(0);
             let other_selflike_exprs = discr_exprs;
-            let discr_field = FieldInfo { span, name: None, self_expr, other_selflike_exprs };
+            let discr_field =
+                FieldInfo { span, name: None, self_expr, other_selflike_exprs, maybe_scalar: true };
 
             let discr_let_stmts: ThinVec<_> = iter::zip(&discr_idents, &selflike_args)
                 .map(|(&ident, selflike_arg)| {
@@ -1533,6 +1535,7 @@ impl<'a> TraitDef<'a> {
                     name: struct_field.ident,
                     self_expr,
                     other_selflike_exprs,
+                    maybe_scalar: struct_field.ty.peel_refs().kind.maybe_scalar(),
                 }
             })
             .collect()

compiler/rustc_builtin_macros/src/deriving/mod.rs

@@ -57,7 +57,7 @@ impl MultiItemModifier for BuiltinDerive {
         let mut items = Vec::new();
         match item {
             Annotatable::Stmt(stmt) => {
-                if let ast::StmtKind::Item(item) = stmt.into_inner().kind {
+                if let ast::StmtKind::Item(item) = stmt.kind {
                     (self.0)(
                         ecx,
                         span,

compiler/rustc_builtin_macros/src/iter.rs

@@ -0,0 +1,53 @@
+use rustc_ast::ptr::P;
+use rustc_ast::tokenstream::TokenStream;
+use rustc_ast::{CoroutineKind, DUMMY_NODE_ID, Expr, ast, token};
+use rustc_errors::PResult;
+use rustc_expand::base::{self, DummyResult, ExpandResult, ExtCtxt, MacroExpanderResult};
+use rustc_span::Span;
+
+pub(crate) fn expand<'cx>(
+    cx: &'cx mut ExtCtxt<'_>,
+    sp: Span,
+    tts: TokenStream,
+) -> MacroExpanderResult<'cx> {
+    let closure = match parse_closure(cx, sp, tts) {
+        Ok(parsed) => parsed,
+        Err(err) => {
+            return ExpandResult::Ready(DummyResult::any(sp, err.emit()));
+        }
+    };
+
+    ExpandResult::Ready(base::MacEager::expr(closure))
+}
+
+fn parse_closure<'a>(
+    cx: &mut ExtCtxt<'a>,
+    span: Span,
+    stream: TokenStream,
+) -> PResult<'a, P<Expr>> {
+    let mut closure_parser = cx.new_parser_from_tts(stream);
+
+    let coroutine_kind = Some(CoroutineKind::Gen {
+        span,
+        closure_id: DUMMY_NODE_ID,
+        return_impl_trait_id: DUMMY_NODE_ID,
+    });
+
+    let mut closure = closure_parser.parse_expr()?;
+    match &mut closure.kind {
+        ast::ExprKind::Closure(c) => {
+            if let Some(kind) = c.coroutine_kind {
+                cx.dcx().span_err(kind.span(), "only plain closures allowed in `iter!`");
+            }
+            c.coroutine_kind = coroutine_kind;
+            if closure_parser.token != token::Eof {
+                closure_parser.unexpected()?;
+            }
+            Ok(closure)
+        }
+        _ => {
+            cx.dcx().span_err(closure.span, "`iter!` body must be a closure");
+            Err(closure_parser.unexpected().unwrap_err())
+        }
+    }
+}

compiler/rustc_builtin_macros/src/lib.rs

@@ -47,6 +47,7 @@ mod errors;
 mod format;
 mod format_foreign;
 mod global_allocator;
+mod iter;
 mod log_syntax;
 mod pattern_type;
 mod source_util;
@@ -95,6 +96,7 @@ pub fn register_builtin_macros(resolver: &mut dyn ResolverExpand) {
         include: source_util::expand_include,
         include_bytes: source_util::expand_include_bytes,
         include_str: source_util::expand_include_str,
+        iter: iter::expand,
         line: source_util::expand_line,
         log_syntax: log_syntax::expand_log_syntax,
         module_path: source_util::expand_mod,

compiler/rustc_builtin_macros/src/pattern_type.rs

@@ -30,14 +30,12 @@ fn parse_pat_ty<'a>(cx: &mut ExtCtxt<'a>, stream: TokenStream) -> PResult<'a, (P
 
     let pat = pat_to_ty_pat(
         cx,
-        parser
-            .parse_pat_no_top_guard(
-                None,
-                RecoverComma::No,
-                RecoverColon::No,
-                CommaRecoveryMode::EitherTupleOrPipe,
-            )?
-            .into_inner(),
+        *parser.parse_pat_no_top_guard(
+            None,
+            RecoverComma::No,
+            RecoverColon::No,
+            CommaRecoveryMode::EitherTupleOrPipe,
+        )?,
     );
 
     if parser.token != token::Eof {
@@ -58,9 +56,9 @@ fn pat_to_ty_pat(cx: &mut ExtCtxt<'_>, pat: ast::Pat) -> P<TyPat> {
             end.map(|value| P(AnonConst { id: DUMMY_NODE_ID, value })),
             include_end,
         ),
-        ast::PatKind::Or(variants) => TyPatKind::Or(
-            variants.into_iter().map(|pat| pat_to_ty_pat(cx, pat.into_inner())).collect(),
-        ),
+        ast::PatKind::Or(variants) => {
+            TyPatKind::Or(variants.into_iter().map(|pat| pat_to_ty_pat(cx, *pat)).collect())
+        }
         ast::PatKind::Err(guar) => TyPatKind::Err(guar),
         _ => TyPatKind::Err(cx.dcx().span_err(pat.span, "pattern not supported in pattern types")),
     };

compiler/rustc_builtin_macros/src/proc_macro_harness.rs

@@ -354,30 +354,28 @@ fn mk_decls(cx: &mut ExtCtxt<'_>, macros: &[ProcMacro]) -> P<ast::Item> {
         })
         .collect();
 
-    let decls_static = cx
-        .item_static(
+    let mut decls_static = cx.item_static(
+        span,
+        Ident::new(sym::_DECLS, span),
+        cx.ty_ref(
             span,
-            Ident::new(sym::_DECLS, span),
-            cx.ty_ref(
+            cx.ty(
                 span,
-                cx.ty(
-                    span,
-                    ast::TyKind::Slice(
-                        cx.ty_path(cx.path(span, vec![proc_macro, bridge, client, proc_macro_ty])),
-                    ),
+                ast::TyKind::Slice(
+                    cx.ty_path(cx.path(span, vec![proc_macro, bridge, client, proc_macro_ty])),
                 ),
-                None,
-                ast::Mutability::Not,
             ),
+            None,
             ast::Mutability::Not,
-            cx.expr_array_ref(span, decls),
-        )
-        .map(|mut i| {
-            i.attrs.push(cx.attr_word(sym::rustc_proc_macro_decls, span));
-            i.attrs.push(cx.attr_word(sym::used, span));
-            i.attrs.push(cx.attr_nested_word(sym::allow, sym::deprecated, span));
-            i
-        });
+        ),
+        ast::Mutability::Not,
+        cx.expr_array_ref(span, decls),
+    );
+    decls_static.attrs.extend([
+        cx.attr_word(sym::rustc_proc_macro_decls, span),
+        cx.attr_word(sym::used, span),
+        cx.attr_nested_word(sym::allow, sym::deprecated, span),
+    ]);
 
     let block = cx.expr_block(
         cx.block(span, thin_vec![cx.stmt_item(span, krate), cx.stmt_item(span, decls_static)]),

compiler/rustc_builtin_macros/src/test.rs

@@ -40,7 +40,7 @@ pub(crate) fn expand_test_case(
     let (mut item, is_stmt) = match anno_item {
         Annotatable::Item(item) => (item, false),
         Annotatable::Stmt(stmt) if let ast::StmtKind::Item(_) = stmt.kind => {
-            if let ast::StmtKind::Item(i) = stmt.into_inner().kind {
+            if let ast::StmtKind::Item(i) = stmt.kind {
                 (i, true)
             } else {
                 unreachable!()
@@ -120,11 +120,7 @@ pub(crate) fn expand_test_or_bench(
         Annotatable::Item(i) => (i, false),
         Annotatable::Stmt(stmt) if matches!(stmt.kind, ast::StmtKind::Item(_)) => {
             // FIXME: Use an 'if let' guard once they are implemented
-            if let ast::StmtKind::Item(i) = stmt.into_inner().kind {
-                (i, true)
-            } else {
-                unreachable!()
-            }
+            if let ast::StmtKind::Item(i) = stmt.kind { (i, true) } else { unreachable!() }
         }
         other => {
             not_testable_error(cx, attr_sp, None);
@@ -381,10 +377,7 @@ pub(crate) fn expand_test_or_bench(
                 .into(),
             ),
         );
-    test_const = test_const.map(|mut tc| {
-        tc.vis.kind = ast::VisibilityKind::Public;
-        tc
-    });
+    test_const.vis.kind = ast::VisibilityKind::Public;
 
     // extern crate test
     let test_extern =

compiler/rustc_codegen_cranelift/build_system/utils.rs

@@ -213,11 +213,13 @@ pub(crate) fn copy_dir_recursively(from: &Path, to: &Path) {
         if filename == "." || filename == ".." {
             continue;
         }
+        let src = from.join(&filename);
+        let dst = to.join(&filename);
         if entry.metadata().unwrap().is_dir() {
-            fs::create_dir(to.join(&filename)).unwrap();
-            copy_dir_recursively(&from.join(&filename), &to.join(&filename));
+            fs::create_dir(&dst).unwrap_or_else(|e| panic!("failed to create {dst:?}: {e}"));
+            copy_dir_recursively(&src, &dst);
         } else {
-            fs::copy(from.join(&filename), to.join(&filename)).unwrap();
+            fs::copy(&src, &dst).unwrap_or_else(|e| panic!("failed to copy {src:?}->{dst:?}: {e}"));
         }
     }
 }

compiler/rustc_codegen_cranelift/example/neon.rs

@@ -233,7 +233,7 @@ unsafe fn test_vaddvq_f32() {
 
 #[cfg(target_arch = "aarch64")]
 unsafe fn test_vrndnq_f32() {
-    // AArch64 llvm intrinsic: llvm.aarch64.neon.frintn.v4f32
+    // llvm intrinsic: llvm.roundeven.v4f32
     let a = f32x4::from([0.1, -1.9, 4.5, 5.5]);
     let e = f32x4::from([0., -2., 4., 6.]);
     let r: f32x4 = transmute(vrndnq_f32(transmute(a)));

compiler/rustc_codegen_cranelift/src/abi/mod.rs

@@ -10,7 +10,7 @@ use std::mem;
 use cranelift_codegen::ir::{ArgumentPurpose, SigRef};
 use cranelift_codegen::isa::CallConv;
 use cranelift_module::ModuleError;
-use rustc_abi::ExternAbi;
+use rustc_abi::{CanonAbi, ExternAbi, X86Call};
 use rustc_codegen_ssa::base::is_call_from_compiler_builtins_to_upstream_monomorphization;
 use rustc_codegen_ssa::errors::CompilerBuiltinsCannotCall;
 use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags;
@@ -19,7 +19,7 @@ use rustc_middle::ty::layout::FnAbiOf;
 use rustc_middle::ty::print::with_no_trimmed_paths;
 use rustc_session::Session;
 use rustc_span::source_map::Spanned;
-use rustc_target::callconv::{Conv, FnAbi, PassMode};
+use rustc_target::callconv::{FnAbi, PassMode};
 use smallvec::SmallVec;
 
 use self::pass_mode::*;
@@ -42,32 +42,27 @@ fn clif_sig_from_fn_abi<'tcx>(
     Signature { params, returns, call_conv }
 }
 
-pub(crate) fn conv_to_call_conv(sess: &Session, c: Conv, default_call_conv: CallConv) -> CallConv {
+pub(crate) fn conv_to_call_conv(
+    sess: &Session,
+    c: CanonAbi,
+    default_call_conv: CallConv,
+) -> CallConv {
     match c {
-        Conv::Rust | Conv::C => default_call_conv,
-        Conv::Cold | Conv::PreserveMost | Conv::PreserveAll => CallConv::Cold,
-        Conv::X86_64SysV => CallConv::SystemV,
-        Conv::X86_64Win64 => CallConv::WindowsFastcall,
+        CanonAbi::Rust | CanonAbi::C => default_call_conv,
+        CanonAbi::RustCold => CallConv::Cold,
 
-        // Should already get a back compat warning
-        Conv::X86Fastcall | Conv::X86Stdcall | Conv::X86ThisCall | Conv::X86VectorCall => {
-            default_call_conv
-        }
+        CanonAbi::X86(x86_call) => match x86_call {
+            X86Call::SysV64 => CallConv::SystemV,
+            X86Call::Win64 => CallConv::WindowsFastcall,
+            // Should already get a back compat warning
+            _ => default_call_conv,
+        },
 
-        Conv::X86Intr | Conv::RiscvInterrupt { .. } => {
-            sess.dcx().fatal(format!("interrupt call conv {c:?} not yet implemented"))
+        CanonAbi::Interrupt(_) | CanonAbi::Arm(_) => {
+            sess.dcx().fatal("call conv {c:?} is not yet implemented")
         }
-
-        Conv::ArmAapcs => sess.dcx().fatal("aapcs call conv not yet implemented"),
-        Conv::CCmseNonSecureCall => {
-            sess.dcx().fatal("C-cmse-nonsecure-call call conv is not yet implemented");
-        }
-        Conv::CCmseNonSecureEntry => {
-            sess.dcx().fatal("C-cmse-nonsecure-entry call conv is not yet implemented");
-        }
-
-        Conv::Msp430Intr | Conv::GpuKernel | Conv::AvrInterrupt | Conv::AvrNonBlockingInterrupt => {
-            unreachable!("tried to use {c:?} call conv which only exists on an unsupported target");
+        CanonAbi::GpuKernel => {
+            unreachable!("tried to use {c:?} call conv which only exists on an unsupported target")
         }
     }
 }
@@ -610,7 +605,7 @@ pub(crate) fn codegen_terminator_call<'tcx>(
         target: CallTarget,
         call_args: &mut Vec<Value>,
     ) {
-        if fn_abi.conv != Conv::C {
+        if fn_abi.conv != CanonAbi::C {
             fx.tcx.dcx().span_fatal(
                 source_info.span,
                 format!("Variadic call for non-C abi {:?}", fn_abi.conv),

compiler/rustc_codegen_cranelift/src/base.rs

@@ -380,7 +380,7 @@ fn codegen_fn_body(fx: &mut FunctionCx<'_, '_, '_>, start_block: Block) {
                             rustc_hir::LangItem::PanicBoundsCheck,
                             &[index, len, location],
                             *unwind,
-                            Some(source_info.span),
+                            source_info.span,
                         );
                     }
                     AssertKind::MisalignedPointerDereference { ref required, ref found } => {
@@ -393,7 +393,7 @@ fn codegen_fn_body(fx: &mut FunctionCx<'_, '_, '_>, start_block: Block) {
                             rustc_hir::LangItem::PanicMisalignedPointerDereference,
                             &[required, found, location],
                             *unwind,
-                            Some(source_info.span),
+                            source_info.span,
                         );
                     }
                     AssertKind::NullPointerDereference => {
@@ -404,7 +404,7 @@ fn codegen_fn_body(fx: &mut FunctionCx<'_, '_, '_>, start_block: Block) {
                             rustc_hir::LangItem::PanicNullPointerDereference,
                             &[location],
                             *unwind,
-                            Some(source_info.span),
+                            source_info.span,
                         )
                     }
                     _ => {
@@ -415,7 +415,7 @@ fn codegen_fn_body(fx: &mut FunctionCx<'_, '_, '_>, start_block: Block) {
                             msg.panic_function(),
                             &[location],
                             *unwind,
-                            Some(source_info.span),
+                            source_info.span,
                         );
                     }
                 }
@@ -531,7 +531,7 @@ fn codegen_fn_body(fx: &mut FunctionCx<'_, '_, '_>, start_block: Block) {
                 );
             }
             TerminatorKind::UnwindTerminate(reason) => {
-                codegen_unwind_terminate(fx, Some(source_info.span), *reason);
+                codegen_unwind_terminate(fx, source_info.span, *reason);
             }
             TerminatorKind::UnwindResume => {
                 // FIXME implement unwinding
@@ -1074,7 +1074,7 @@ pub(crate) fn codegen_operand<'tcx>(
 pub(crate) fn codegen_panic_nounwind<'tcx>(
     fx: &mut FunctionCx<'_, '_, 'tcx>,
     msg_str: &str,
-    span: Option<Span>,
+    span: Span,
 ) {
     let msg_ptr = fx.anonymous_str(msg_str);
     let msg_len = fx.bcx.ins().iconst(fx.pointer_type, i64::try_from(msg_str.len()).unwrap());
@@ -1091,7 +1091,7 @@ pub(crate) fn codegen_panic_nounwind<'tcx>(
 
 pub(crate) fn codegen_unwind_terminate<'tcx>(
     fx: &mut FunctionCx<'_, '_, 'tcx>,
-    span: Option<Span>,
+    span: Span,
     reason: UnwindTerminateReason,
 ) {
     codegen_panic_inner(fx, reason.lang_item(), &[], UnwindAction::Unreachable, span);
@@ -1102,7 +1102,7 @@ fn codegen_panic_inner<'tcx>(
     lang_item: rustc_hir::LangItem,
     args: &[Value],
     _unwind: UnwindAction,
-    span: Option<Span>,
+    span: Span,
 ) {
     fx.bcx.set_cold_block(fx.bcx.current_block().unwrap());
 

compiler/rustc_codegen_cranelift/src/discriminant.rs

@@ -28,7 +28,7 @@ pub(crate) fn codegen_set_discriminant<'tcx>(
             tag_encoding: TagEncoding::Direct,
             variants: _,
         } => {
-            let ptr = place.place_field(fx, FieldIdx::new(tag_field));
+            let ptr = place.place_field(fx, tag_field);
             let to = layout.ty.discriminant_for_variant(fx.tcx, variant_index).unwrap().val;
             let to = match ptr.layout().ty.kind() {
                 ty::Uint(UintTy::U128) | ty::Int(IntTy::I128) => {
@@ -53,7 +53,7 @@ pub(crate) fn codegen_set_discriminant<'tcx>(
             variants: _,
         } => {
             if variant_index != untagged_variant {
-                let niche = place.place_field(fx, FieldIdx::new(tag_field));
+                let niche = place.place_field(fx, tag_field);
                 let niche_type = fx.clif_type(niche.layout().ty).unwrap();
                 let niche_value = variant_index.as_u32() - niche_variants.start().as_u32();
                 let niche_value = (niche_value as u128).wrapping_add(niche_start);
@@ -118,7 +118,7 @@ pub(crate) fn codegen_get_discriminant<'tcx>(
     let cast_to = fx.clif_type(dest_layout.ty).unwrap();
 
     // Read the tag/niche-encoded discriminant from memory.
-    let tag = value.value_field(fx, FieldIdx::new(tag_field));
+    let tag = value.value_field(fx, tag_field);
     let tag = tag.load_scalar(fx);
 
     // Decode the discriminant (specifically if it's niche-encoded).

compiler/rustc_codegen_cranelift/src/inline_asm.rs

@@ -850,7 +850,7 @@ fn asm_clif_type<'tcx>(fx: &FunctionCx<'_, '_, 'tcx>, ty: Ty<'tcx>) -> Option<ty
         // Adapted from https://github.com/rust-lang/rust/blob/f3c66088610c1b80110297c2d9a8b5f9265b013f/compiler/rustc_hir_analysis/src/check/intrinsicck.rs#L136-L151
         ty::Adt(adt, args) if fx.tcx.is_lang_item(adt.did(), LangItem::MaybeUninit) => {
             let fields = &adt.non_enum_variant().fields;
-            let ty = fields[FieldIdx::from_u32(1)].ty(fx.tcx, args);
+            let ty = fields[FieldIdx::ONE].ty(fx.tcx, args);
             let ty::Adt(ty, args) = ty.kind() else {
                 unreachable!("expected first field of `MaybeUninit` to be an ADT")
             };

compiler/rustc_codegen_cranelift/src/intrinsics/llvm.rs

@@ -62,6 +62,14 @@ pub(crate) fn codegen_llvm_intrinsic_call<'tcx>(
             });
         }
 
+        _ if intrinsic.starts_with("llvm.roundeven.v") => {
+            intrinsic_args!(fx, args => (v); intrinsic);
+
+            simd_for_each_lane(fx, v, ret, &|fx, _lane_ty, _res_lane_ty, lane| {
+                fx.bcx.ins().nearest(lane)
+            });
+        }
+
         _ => {
             fx.tcx
                 .dcx()
@@ -71,7 +79,7 @@ pub(crate) fn codegen_llvm_intrinsic_call<'tcx>(
                  See https://github.com/rust-lang/rustc_codegen_cranelift/issues/171\n\
                  Please open an issue at https://github.com/rust-lang/rustc_codegen_cranelift/issues"
             );
-            crate::base::codegen_panic_nounwind(fx, &msg, None);
+            crate::base::codegen_panic_nounwind(fx, &msg, span);
             return;
         }
     }

compiler/rustc_codegen_cranelift/src/intrinsics/llvm_aarch64.rs

@@ -264,14 +264,6 @@ pub(super) fn codegen_aarch64_llvm_intrinsic_call<'tcx>(
             simd_reduce(fx, v, None, ret, &|fx, _ty, a, b| fx.bcx.ins().fadd(a, b));
         }
 
-        _ if intrinsic.starts_with("llvm.aarch64.neon.frintn.v") => {
-            intrinsic_args!(fx, args => (v); intrinsic);
-
-            simd_for_each_lane(fx, v, ret, &|fx, _lane_ty, _res_lane_ty, lane| {
-                fx.bcx.ins().nearest(lane)
-            });
-        }
-
         _ if intrinsic.starts_with("llvm.aarch64.neon.smaxv.i") => {
             intrinsic_args!(fx, args => (v); intrinsic);
 
@@ -512,7 +504,7 @@ pub(super) fn codegen_aarch64_llvm_intrinsic_call<'tcx>(
                  See https://github.com/rust-lang/rustc_codegen_cranelift/issues/171\n\
                  Please open an issue at https://github.com/rust-lang/rustc_codegen_cranelift/issues"
             );
-            crate::base::codegen_panic_nounwind(fx, &msg, None);
+            crate::base::codegen_panic_nounwind(fx, &msg, fx.mir.span);
             return;
         }
     }

compiler/rustc_codegen_cranelift/src/intrinsics/llvm_x86.rs

@@ -1321,7 +1321,7 @@ pub(super) fn codegen_x86_llvm_intrinsic_call<'tcx>(
                  See https://github.com/rust-lang/rustc_codegen_cranelift/issues/171\n\
                  Please open an issue at https://github.com/rust-lang/rustc_codegen_cranelift/issues"
             );
-            crate::base::codegen_panic_nounwind(fx, &msg, None);
+            crate::base::codegen_panic_nounwind(fx, &msg, span);
             return;
         }
     }

compiler/rustc_codegen_cranelift/src/intrinsics/mod.rs

@@ -785,7 +785,7 @@ fn codegen_regular_intrinsic_call<'tcx>(
                             }
                         })
                     });
-                    crate::base::codegen_panic_nounwind(fx, &msg_str, Some(source_info.span));
+                    crate::base::codegen_panic_nounwind(fx, &msg_str, source_info.span);
                     return Ok(());
                 }
             }
@@ -875,7 +875,6 @@ fn codegen_regular_intrinsic_call<'tcx>(
             let ptr = ptr.load_scalar(fx);
 
             let ty = generic_args.type_at(0);
-            let _ord = generic_args.const_at(1).to_value(); // FIXME: forward this to cranelift once they support that
             match ty.kind() {
                 ty::Uint(UintTy::U128) | ty::Int(IntTy::I128) => {
                     // FIXME implement 128bit atomics
@@ -884,7 +883,7 @@ fn codegen_regular_intrinsic_call<'tcx>(
                         crate::base::codegen_panic_nounwind(
                             fx,
                             "128bit atomics not yet supported",
-                            None,
+                            source_info.span,
                         );
                         return Ok(());
                     } else {
@@ -906,7 +905,7 @@ fn codegen_regular_intrinsic_call<'tcx>(
             let val = CValue::by_val(val, fx.layout_of(ty));
             ret.write_cvalue(fx, val);
         }
-        _ if intrinsic.as_str().starts_with("atomic_store") => {
+        sym::atomic_store => {
             intrinsic_args!(fx, args => (ptr, val); intrinsic);
             let ptr = ptr.load_scalar(fx);
 
@@ -919,7 +918,7 @@ fn codegen_regular_intrinsic_call<'tcx>(
                         crate::base::codegen_panic_nounwind(
                             fx,
                             "128bit atomics not yet supported",
-                            None,
+                            source_info.span,
                         );
                         return Ok(());
                     } else {
@@ -939,7 +938,7 @@ fn codegen_regular_intrinsic_call<'tcx>(
 
             fx.bcx.ins().atomic_store(MemFlags::trusted(), val, ptr);
         }
-        _ if intrinsic.as_str().starts_with("atomic_xchg") => {
+        sym::atomic_xchg => {
             intrinsic_args!(fx, args => (ptr, new); intrinsic);
             let ptr = ptr.load_scalar(fx);
 
@@ -960,8 +959,7 @@ fn codegen_regular_intrinsic_call<'tcx>(
             let old = CValue::by_val(old, layout);
             ret.write_cvalue(fx, old);
         }
-        _ if intrinsic.as_str().starts_with("atomic_cxchg") => {
-            // both atomic_cxchg_* and atomic_cxchgweak_*
+        sym::atomic_cxchg | sym::atomic_cxchgweak => {
             intrinsic_args!(fx, args => (ptr, test_old, new); intrinsic);
             let ptr = ptr.load_scalar(fx);
 
@@ -984,7 +982,7 @@ fn codegen_regular_intrinsic_call<'tcx>(
             ret.write_cvalue(fx, ret_val)
         }
 
-        _ if intrinsic.as_str().starts_with("atomic_xadd") => {
+        sym::atomic_xadd => {
             intrinsic_args!(fx, args => (ptr, amount); intrinsic);
             let ptr = ptr.load_scalar(fx);
 
@@ -1006,7 +1004,7 @@ fn codegen_regular_intrinsic_call<'tcx>(
             let old = CValue::by_val(old, layout);
             ret.write_cvalue(fx, old);
         }
-        _ if intrinsic.as_str().starts_with("atomic_xsub") => {
+        sym::atomic_xsub => {
             intrinsic_args!(fx, args => (ptr, amount); intrinsic);
             let ptr = ptr.load_scalar(fx);
 
@@ -1028,7 +1026,7 @@ fn codegen_regular_intrinsic_call<'tcx>(
             let old = CValue::by_val(old, layout);
             ret.write_cvalue(fx, old);
         }
-        _ if intrinsic.as_str().starts_with("atomic_and") => {
+        sym::atomic_and => {
             intrinsic_args!(fx, args => (ptr, src); intrinsic);
             let ptr = ptr.load_scalar(fx);
 
@@ -1049,7 +1047,7 @@ fn codegen_regular_intrinsic_call<'tcx>(
             let old = CValue::by_val(old, layout);
             ret.write_cvalue(fx, old);
         }
-        _ if intrinsic.as_str().starts_with("atomic_or") => {
+        sym::atomic_or => {
             intrinsic_args!(fx, args => (ptr, src); intrinsic);
             let ptr = ptr.load_scalar(fx);
 
@@ -1070,7 +1068,7 @@ fn codegen_regular_intrinsic_call<'tcx>(
             let old = CValue::by_val(old, layout);
             ret.write_cvalue(fx, old);
         }
-        _ if intrinsic.as_str().starts_with("atomic_xor") => {
+        sym::atomic_xor => {
             intrinsic_args!(fx, args => (ptr, src); intrinsic);
             let ptr = ptr.load_scalar(fx);
 
@@ -1091,7 +1089,7 @@ fn codegen_regular_intrinsic_call<'tcx>(
             let old = CValue::by_val(old, layout);
             ret.write_cvalue(fx, old);
         }
-        _ if intrinsic.as_str().starts_with("atomic_nand") => {
+        sym::atomic_nand => {
             intrinsic_args!(fx, args => (ptr, src); intrinsic);
             let ptr = ptr.load_scalar(fx);
 
@@ -1112,7 +1110,7 @@ fn codegen_regular_intrinsic_call<'tcx>(
             let old = CValue::by_val(old, layout);
             ret.write_cvalue(fx, old);
         }
-        _ if intrinsic.as_str().starts_with("atomic_max") => {
+        sym::atomic_max => {
             intrinsic_args!(fx, args => (ptr, src); intrinsic);
             let ptr = ptr.load_scalar(fx);
 
@@ -1133,7 +1131,7 @@ fn codegen_regular_intrinsic_call<'tcx>(
             let old = CValue::by_val(old, layout);
             ret.write_cvalue(fx, old);
         }
-        _ if intrinsic.as_str().starts_with("atomic_umax") => {
+        sym::atomic_umax => {
             intrinsic_args!(fx, args => (ptr, src); intrinsic);
             let ptr = ptr.load_scalar(fx);
 
@@ -1154,7 +1152,7 @@ fn codegen_regular_intrinsic_call<'tcx>(
             let old = CValue::by_val(old, layout);
             ret.write_cvalue(fx, old);
         }
-        _ if intrinsic.as_str().starts_with("atomic_min") => {
+        sym::atomic_min => {
             intrinsic_args!(fx, args => (ptr, src); intrinsic);
             let ptr = ptr.load_scalar(fx);
 
@@ -1175,7 +1173,7 @@ fn codegen_regular_intrinsic_call<'tcx>(
             let old = CValue::by_val(old, layout);
             ret.write_cvalue(fx, old);
         }
-        _ if intrinsic.as_str().starts_with("atomic_umin") => {
+        sym::atomic_umin => {
             intrinsic_args!(fx, args => (ptr, src); intrinsic);
             let ptr = ptr.load_scalar(fx);
 

compiler/rustc_codegen_cranelift/src/main_shim.rs

@@ -101,7 +101,7 @@ pub(crate) fn maybe_create_entry_wrapper(
                 let call_inst = bcx.ins().call(main_func_ref, &[]);
                 let call_results = bcx.func.dfg.inst_results(call_inst).to_owned();
 
-                let termination_trait = tcx.require_lang_item(LangItem::Termination, None);
+                let termination_trait = tcx.require_lang_item(LangItem::Termination, DUMMY_SP);
                 let report = tcx
                     .associated_items(termination_trait)
                     .find_by_ident_and_kind(
@@ -136,7 +136,7 @@ pub(crate) fn maybe_create_entry_wrapper(
                 }
             } else {
                 // Regular main fn invoked via start lang item.
-                let start_def_id = tcx.require_lang_item(LangItem::Start, None);
+                let start_def_id = tcx.require_lang_item(LangItem::Start, DUMMY_SP);
                 let start_instance = Instance::expect_resolve(
                     tcx,
                     ty::TypingEnv::fully_monomorphized(),

compiler/rustc_codegen_cranelift/src/num.rs

@@ -54,7 +54,7 @@ fn codegen_three_way_compare<'tcx>(
     let gt = fx.bcx.ins().icmp(gt_cc, lhs, rhs);
     let lt = fx.bcx.ins().icmp(lt_cc, lhs, rhs);
     let val = fx.bcx.ins().isub(gt, lt);
-    CValue::by_val(val, fx.layout_of(fx.tcx.ty_ordering_enum(Some(fx.mir.span))))
+    CValue::by_val(val, fx.layout_of(fx.tcx.ty_ordering_enum(fx.mir.span)))
 }
 
 fn codegen_compare_bin_op<'tcx>(

compiler/rustc_codegen_cranelift/src/unsize.rs

@@ -240,7 +240,7 @@ pub(crate) fn size_and_align_of<'tcx>(
                 })
             });
 
-            codegen_panic_nounwind(fx, &msg_str, None);
+            codegen_panic_nounwind(fx, &msg_str, fx.mir.span);
 
             fx.bcx.switch_to_block(next_block);
 

compiler/rustc_codegen_cranelift/src/vtable.rs

@@ -53,7 +53,7 @@ pub(crate) fn get_ptr_and_method_ref<'tcx>(
                     .layout()
                     .non_1zst_field(fx)
                     .expect("not exactly one non-1-ZST field in a `DispatchFromDyn` type");
-                arg = arg.value_field(fx, FieldIdx::new(idx));
+                arg = arg.value_field(fx, idx);
             }
         }
 
@@ -62,8 +62,7 @@ pub(crate) fn get_ptr_and_method_ref<'tcx>(
                 let inner_layout = fx.layout_of(arg.layout().ty.builtin_deref(true).unwrap());
                 let dyn_star = CPlace::for_ptr(Pointer::new(arg.load_scalar(fx)), inner_layout);
                 let ptr = dyn_star.place_field(fx, FieldIdx::ZERO).to_ptr();
-                let vtable =
-                    dyn_star.place_field(fx, FieldIdx::new(1)).to_cvalue(fx).load_scalar(fx);
+                let vtable = dyn_star.place_field(fx, FieldIdx::ONE).to_cvalue(fx).load_scalar(fx);
                 break 'block (ptr, vtable);
             }
         }

compiler/rustc_codegen_gcc/src/abi.rs

@@ -1,7 +1,7 @@
 #[cfg(feature = "master")]
 use gccjit::FnAttribute;
 use gccjit::{ToLValue, ToRValue, Type};
-use rustc_abi::{Reg, RegKind};
+use rustc_abi::{ArmCall, CanonAbi, InterruptKind, Reg, RegKind, X86Call};
 use rustc_codegen_ssa::traits::{AbiBuilderMethods, BaseTypeCodegenMethods};
 use rustc_data_structures::fx::FxHashSet;
 use rustc_middle::bug;
@@ -10,8 +10,6 @@ use rustc_middle::ty::layout::LayoutOf;
 #[cfg(feature = "master")]
 use rustc_session::config;
 use rustc_target::callconv::{ArgAttributes, CastTarget, FnAbi, PassMode};
-#[cfg(feature = "master")]
-use rustc_target::callconv::{Conv, RiscvInterruptKind};
 
 use crate::builder::Builder;
 use crate::context::CodegenCx;
@@ -238,29 +236,16 @@ impl<'gcc, 'tcx> FnAbiGccExt<'gcc, 'tcx> for FnAbi<'tcx, Ty<'tcx>> {
 }
 
 #[cfg(feature = "master")]
-pub fn conv_to_fn_attribute<'gcc>(conv: Conv, arch: &str) -> Option<FnAttribute<'gcc>> {
+pub fn conv_to_fn_attribute<'gcc>(conv: CanonAbi, arch: &str) -> Option<FnAttribute<'gcc>> {
     let attribute = match conv {
-        Conv::C | Conv::Rust => return None,
-        Conv::CCmseNonSecureCall => {
-            if arch == "arm" {
-                FnAttribute::ArmCmseNonsecureCall
-            } else {
-                return None;
-            }
-        }
-        Conv::CCmseNonSecureEntry => {
-            if arch == "arm" {
-                FnAttribute::ArmCmseNonsecureEntry
-            } else {
-                return None;
-            }
-        }
-        Conv::Cold => FnAttribute::Cold,
-        // NOTE: the preserve attributes are not yet implemented in GCC:
-        // https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110899
-        Conv::PreserveMost => return None,
-        Conv::PreserveAll => return None,
-        Conv::GpuKernel => {
+        CanonAbi::C | CanonAbi::Rust => return None,
+        CanonAbi::Arm(arm_call) => match arm_call {
+            ArmCall::CCmseNonSecureCall => FnAttribute::ArmCmseNonsecureCall,
+            ArmCall::CCmseNonSecureEntry => FnAttribute::ArmCmseNonsecureEntry,
+            ArmCall::Aapcs => FnAttribute::ArmPcs("aapcs"),
+        },
+        CanonAbi::RustCold => FnAttribute::Cold,
+        CanonAbi::GpuKernel => {
             if arch == "amdgpu" {
                 FnAttribute::GcnAmdGpuHsaKernel
             } else if arch == "nvptx64" {
@@ -270,26 +255,24 @@ pub fn conv_to_fn_attribute<'gcc>(conv: Conv, arch: &str) -> Option<FnAttribute<
             }
         }
         // TODO(antoyo): check if those AVR attributes are mapped correctly.
-        Conv::AvrInterrupt => FnAttribute::AvrSignal,
-        Conv::AvrNonBlockingInterrupt => FnAttribute::AvrInterrupt,
-        Conv::ArmAapcs => FnAttribute::ArmPcs("aapcs"),
-        Conv::Msp430Intr => FnAttribute::Msp430Interrupt,
-        Conv::RiscvInterrupt { kind } => {
-            let kind = match kind {
-                RiscvInterruptKind::Machine => "machine",
-                RiscvInterruptKind::Supervisor => "supervisor",
-            };
-            FnAttribute::RiscvInterrupt(kind)
-        }
-        Conv::X86Fastcall => FnAttribute::X86FastCall,
-        Conv::X86Intr => FnAttribute::X86Interrupt,
-        Conv::X86Stdcall => FnAttribute::X86Stdcall,
-        Conv::X86ThisCall => FnAttribute::X86ThisCall,
-        // NOTE: the vectorcall calling convention is not yet implemented in GCC:
-        // https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89485
-        Conv::X86VectorCall => return None,
-        Conv::X86_64SysV => FnAttribute::X86SysvAbi,
-        Conv::X86_64Win64 => FnAttribute::X86MsAbi,
+        CanonAbi::Interrupt(interrupt_kind) => match interrupt_kind {
+            InterruptKind::Avr => FnAttribute::AvrSignal,
+            InterruptKind::AvrNonBlocking => FnAttribute::AvrInterrupt,
+            InterruptKind::Msp430 => FnAttribute::Msp430Interrupt,
+            InterruptKind::RiscvMachine => FnAttribute::RiscvInterrupt("machine"),
+            InterruptKind::RiscvSupervisor => FnAttribute::RiscvInterrupt("supervisor"),
+            InterruptKind::X86 => FnAttribute::X86Interrupt,
+        },
+        CanonAbi::X86(x86_call) => match x86_call {
+            X86Call::Fastcall => FnAttribute::X86FastCall,
+            X86Call::Stdcall => FnAttribute::X86Stdcall,
+            X86Call::Thiscall => FnAttribute::X86ThisCall,
+            // // NOTE: the vectorcall calling convention is not yet implemented in GCC:
+            // // https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89485
+            X86Call::Vectorcall => return None,
+            X86Call::SysV64 => FnAttribute::X86SysvAbi,
+            X86Call::Win64 => FnAttribute::X86MsAbi,
+        },
     };
     Some(attribute)
 }

compiler/rustc_codegen_gcc/src/debuginfo.rs

@@ -52,10 +52,6 @@ impl<'a, 'gcc, 'tcx> DebugInfoBuilderMethods for Builder<'a, 'gcc, 'tcx> {
     fn clear_dbg_loc(&mut self) {
         self.location = None;
     }
-
-    fn get_dbg_loc(&self) -> Option<Self::DILocation> {
-        self.location
-    }
 }
 
 /// Generate the `debug_context` in an MIR Body.

compiler/rustc_codegen_gcc/src/int.rs

@@ -3,11 +3,11 @@
 //! 128-bit integers on 32-bit platforms and thus require to be handled manually.
 
 use gccjit::{BinaryOp, ComparisonOp, FunctionType, Location, RValue, ToRValue, Type, UnaryOp};
-use rustc_abi::{Endian, ExternAbi};
+use rustc_abi::{CanonAbi, Endian, ExternAbi};
 use rustc_codegen_ssa::common::{IntPredicate, TypeKind};
 use rustc_codegen_ssa::traits::{BackendTypes, BaseTypeCodegenMethods, BuilderMethods, OverflowOp};
 use rustc_middle::ty::{self, Ty};
-use rustc_target::callconv::{ArgAbi, ArgAttributes, Conv, FnAbi, PassMode};
+use rustc_target::callconv::{ArgAbi, ArgAttributes, FnAbi, PassMode};
 
 use crate::builder::{Builder, ToGccComp};
 use crate::common::{SignType, TypeReflection};
@@ -397,7 +397,7 @@ impl<'a, 'gcc, 'tcx> Builder<'a, 'gcc, 'tcx> {
             ret: arg_abi,
             c_variadic: false,
             fixed_count: 3,
-            conv: Conv::C,
+            conv: CanonAbi::C,
             can_unwind: false,
         };
         fn_abi.adjust_for_foreign_abi(self.cx, ExternAbi::C { unwind: false });

compiler/rustc_codegen_gcc/src/intrinsic/mod.rs

@@ -524,11 +524,6 @@ impl<'a, 'gcc, 'tcx> IntrinsicCallBuilderMethods<'tcx> for Builder<'a, 'gcc, 'tc
         cond
     }
 
-    fn type_test(&mut self, _pointer: Self::Value, _typeid: Self::Value) -> Self::Value {
-        // Unsupported.
-        self.context.new_rvalue_from_int(self.int_type, 0)
-    }
-
     fn type_checked_load(
         &mut self,
         _llvtable: Self::Value,

compiler/rustc_codegen_llvm/src/abi.rs

@@ -2,7 +2,10 @@ use std::borrow::Borrow;
 use std::cmp;
 
 use libc::c_uint;
-use rustc_abi::{BackendRepr, HasDataLayout, Primitive, Reg, RegKind, Size};
+use rustc_abi::{
+    ArmCall, BackendRepr, CanonAbi, HasDataLayout, InterruptKind, Primitive, Reg, RegKind, Size,
+    X86Call,
+};
 use rustc_codegen_ssa::MemFlags;
 use rustc_codegen_ssa::mir::operand::{OperandRef, OperandValue};
 use rustc_codegen_ssa::mir::place::{PlaceRef, PlaceValue};
@@ -12,7 +15,7 @@ use rustc_middle::ty::layout::LayoutOf;
 use rustc_middle::{bug, ty};
 use rustc_session::config;
 use rustc_target::callconv::{
-    ArgAbi, ArgAttribute, ArgAttributes, ArgExtension, CastTarget, Conv, FnAbi, PassMode,
+    ArgAbi, ArgAttribute, ArgAttributes, ArgExtension, CastTarget, FnAbi, PassMode,
 };
 use rustc_target::spec::SanitizerSet;
 use smallvec::SmallVec;
@@ -409,11 +412,17 @@ impl<'ll, 'tcx> FnAbiLlvmExt<'ll, 'tcx> for FnAbi<'tcx, Ty<'tcx>> {
         if !self.can_unwind {
             func_attrs.push(llvm::AttributeKind::NoUnwind.create_attr(cx.llcx));
         }
-        if let Conv::RiscvInterrupt { kind } = self.conv {
-            func_attrs.push(llvm::CreateAttrStringValue(cx.llcx, "interrupt", kind.as_str()));
-        }
-        if let Conv::CCmseNonSecureEntry = self.conv {
-            func_attrs.push(llvm::CreateAttrString(cx.llcx, "cmse_nonsecure_entry"))
+        match self.conv {
+            CanonAbi::Interrupt(InterruptKind::RiscvMachine) => {
+                func_attrs.push(llvm::CreateAttrStringValue(cx.llcx, "interrupt", "machine"))
+            }
+            CanonAbi::Interrupt(InterruptKind::RiscvSupervisor) => {
+                func_attrs.push(llvm::CreateAttrStringValue(cx.llcx, "interrupt", "supervisor"))
+            }
+            CanonAbi::Arm(ArmCall::CCmseNonSecureEntry) => {
+                func_attrs.push(llvm::CreateAttrString(cx.llcx, "cmse_nonsecure_entry"))
+            }
+            _ => (),
         }
         attributes::apply_to_llfn(llfn, llvm::AttributePlace::Function, &{ func_attrs });
 
@@ -600,7 +609,7 @@ impl<'ll, 'tcx> FnAbiLlvmExt<'ll, 'tcx> for FnAbi<'tcx, Ty<'tcx>> {
             llvm::SetInstructionCallConv(callsite, cconv);
         }
 
-        if self.conv == Conv::CCmseNonSecureCall {
+        if self.conv == CanonAbi::Arm(ArmCall::CCmseNonSecureCall) {
             // This will probably get ignored on all targets but those supporting the TrustZone-M
             // extension (thumbv8m targets).
             let cmse_nonsecure_call = llvm::CreateAttrString(bx.cx.llcx, "cmse_nonsecure_call");
@@ -636,17 +645,11 @@ impl AbiBuilderMethods for Builder<'_, '_, '_> {
 }
 
 impl llvm::CallConv {
-    pub(crate) fn from_conv(conv: Conv, arch: &str) -> Self {
+    pub(crate) fn from_conv(conv: CanonAbi, arch: &str) -> Self {
         match conv {
-            Conv::C
-            | Conv::Rust
-            | Conv::CCmseNonSecureCall
-            | Conv::CCmseNonSecureEntry
-            | Conv::RiscvInterrupt { .. } => llvm::CCallConv,
-            Conv::Cold => llvm::ColdCallConv,
-            Conv::PreserveMost => llvm::PreserveMost,
-            Conv::PreserveAll => llvm::PreserveAll,
-            Conv::GpuKernel => {
+            CanonAbi::C | CanonAbi::Rust => llvm::CCallConv,
+            CanonAbi::RustCold => llvm::PreserveMost,
+            CanonAbi::GpuKernel => {
                 if arch == "amdgpu" {
                     llvm::AmdgpuKernel
                 } else if arch == "nvptx64" {
@@ -655,17 +658,25 @@ impl llvm::CallConv {
                     panic!("Architecture {arch} does not support GpuKernel calling convention");
                 }
             }
-            Conv::AvrInterrupt => llvm::AvrInterrupt,
-            Conv::AvrNonBlockingInterrupt => llvm::AvrNonBlockingInterrupt,
-            Conv::ArmAapcs => llvm::ArmAapcsCallConv,
-            Conv::Msp430Intr => llvm::Msp430Intr,
-            Conv::X86Fastcall => llvm::X86FastcallCallConv,
-            Conv::X86Intr => llvm::X86_Intr,
-            Conv::X86Stdcall => llvm::X86StdcallCallConv,
-            Conv::X86ThisCall => llvm::X86_ThisCall,
-            Conv::X86VectorCall => llvm::X86_VectorCall,
-            Conv::X86_64SysV => llvm::X86_64_SysV,
-            Conv::X86_64Win64 => llvm::X86_64_Win64,
+            CanonAbi::Interrupt(interrupt_kind) => match interrupt_kind {
+                InterruptKind::Avr => llvm::AvrInterrupt,
+                InterruptKind::AvrNonBlocking => llvm::AvrNonBlockingInterrupt,
+                InterruptKind::Msp430 => llvm::Msp430Intr,
+                InterruptKind::RiscvMachine | InterruptKind::RiscvSupervisor => llvm::CCallConv,
+                InterruptKind::X86 => llvm::X86_Intr,
+            },
+            CanonAbi::Arm(arm_call) => match arm_call {
+                ArmCall::Aapcs => llvm::ArmAapcsCallConv,
+                ArmCall::CCmseNonSecureCall | ArmCall::CCmseNonSecureEntry => llvm::CCallConv,
+            },
+            CanonAbi::X86(x86_call) => match x86_call {
+                X86Call::Fastcall => llvm::X86FastcallCallConv,
+                X86Call::Stdcall => llvm::X86StdcallCallConv,
+                X86Call::SysV64 => llvm::X86_64_SysV,
+                X86Call::Thiscall => llvm::X86_ThisCall,
+                X86Call::Vectorcall => llvm::X86_VectorCall,
+                X86Call::Win64 => llvm::X86_64_Win64,
+            },
         }
     }
 }

compiler/rustc_codegen_llvm/src/builder.rs

@@ -1815,8 +1815,11 @@ impl<'a, 'll, 'tcx> Builder<'a, 'll, 'tcx> {
             let typeid_metadata = self.cx.typeid_metadata(typeid).unwrap();
             let dbg_loc = self.get_dbg_loc();
 
-            // Test whether the function pointer is associated with the type identifier.
-            let cond = self.type_test(llfn, typeid_metadata);
+            // Test whether the function pointer is associated with the type identifier using the
+            // llvm.type.test intrinsic. The LowerTypeTests link-time optimization pass replaces
+            // calls to this intrinsic with code to test type membership.
+            let typeid = self.get_metadata_value(typeid_metadata);
+            let cond = self.call_intrinsic("llvm.type.test", &[llfn, typeid]);
             let bb_pass = self.append_sibling_block("type_test.pass");
             let bb_fail = self.append_sibling_block("type_test.fail");
             self.cond_br(cond, bb_pass, bb_fail);

compiler/rustc_codegen_llvm/src/consts.rs

@@ -541,12 +541,12 @@ impl<'ll> CodegenCx<'ll, '_> {
                 // in the handling of `.init_array` (the static constructor list) in versions of
                 // the gold linker (prior to the one released with binutils 2.36).
                 //
-                // That said, we only ever emit these when compiling for ELF targets, unless
-                // `#[used(compiler)]` is explicitly requested. This is to avoid similar breakage
-                // on other targets, in particular MachO targets have *their* static constructor
-                // lists broken if `llvm.compiler.used` is emitted rather than `llvm.used`. However,
-                // that check happens when assigning the `CodegenFnAttrFlags` in
-                // `rustc_hir_analysis`, so we don't need to take care of it here.
+                // That said, we only ever emit these when `#[used(compiler)]` is explicitly
+                // requested. This is to avoid similar breakage on other targets, in particular
+                // MachO targets have *their* static constructor lists broken if `llvm.compiler.used`
+                // is emitted rather than `llvm.used`. However, that check happens when assigning
+                // the `CodegenFnAttrFlags` in the `codegen_fn_attrs` query, so we don't need to
+                // take care of it here.
                 self.add_compiler_used_global(g);
             }
             if attrs.flags.contains(CodegenFnAttrFlags::USED_LINKER) {

compiler/rustc_codegen_llvm/src/debuginfo/metadata/enums/cpp_like.rs

@@ -1,7 +1,7 @@
 use std::borrow::Cow;
 
 use libc::c_uint;
-use rustc_abi::{Align, Endian, Size, TagEncoding, VariantIdx, Variants};
+use rustc_abi::{Align, Endian, FieldIdx, Size, TagEncoding, VariantIdx, Variants};
 use rustc_codegen_ssa::debuginfo::type_names::compute_debuginfo_type_name;
 use rustc_codegen_ssa::debuginfo::{tag_base_type, wants_c_like_enum_debuginfo};
 use rustc_codegen_ssa::traits::{ConstCodegenMethods, MiscCodegenMethods};
@@ -401,7 +401,7 @@ fn build_union_fields_for_enum<'ll, 'tcx>(
     enum_type_and_layout: TyAndLayout<'tcx>,
     enum_type_di_node: &'ll DIType,
     variant_indices: impl Iterator<Item = VariantIdx> + Clone,
-    tag_field: usize,
+    tag_field: FieldIdx,
     untagged_variant_index: Option<VariantIdx>,
 ) -> SmallVec<&'ll DIType> {
     let tag_base_type = tag_base_type(cx.tcx, enum_type_and_layout);
@@ -805,7 +805,7 @@ fn build_union_fields_for_direct_tag_enum_or_coroutine<'ll, 'tcx>(
     variant_field_infos: &[VariantFieldInfo<'ll>],
     discr_type_di_node: &'ll DIType,
     tag_base_type: Ty<'tcx>,
-    tag_field: usize,
+    tag_field: FieldIdx,
     untagged_variant_index: Option<VariantIdx>,
     di_flags: DIFlags,
 ) -> SmallVec<&'ll DIType> {
@@ -858,7 +858,7 @@ fn build_union_fields_for_direct_tag_enum_or_coroutine<'ll, 'tcx>(
     }));
 
     assert_eq!(
-        cx.size_and_align_of(enum_type_and_layout.field(cx, tag_field).ty),
+        cx.size_and_align_of(enum_type_and_layout.field(cx, tag_field.as_usize()).ty),
         cx.size_and_align_of(self::tag_base_type(cx.tcx, enum_type_and_layout))
     );
 
@@ -875,7 +875,7 @@ fn build_union_fields_for_direct_tag_enum_or_coroutine<'ll, 'tcx>(
             Endian::Big => (8, 0),
         };
 
-        let tag_field_offset = enum_type_and_layout.fields.offset(tag_field).bytes();
+        let tag_field_offset = enum_type_and_layout.fields.offset(tag_field.as_usize()).bytes();
         let lo_offset = Size::from_bytes(tag_field_offset + lo_offset);
         let hi_offset = Size::from_bytes(tag_field_offset + hi_offset);
 
@@ -905,8 +905,8 @@ fn build_union_fields_for_direct_tag_enum_or_coroutine<'ll, 'tcx>(
             cx,
             enum_type_di_node,
             TAG_FIELD_NAME,
-            enum_type_and_layout.field(cx, tag_field),
-            enum_type_and_layout.fields.offset(tag_field),
+            enum_type_and_layout.field(cx, tag_field.as_usize()),
+            enum_type_and_layout.fields.offset(tag_field.as_usize()),
             di_flags,
             tag_base_type_di_node,
             None,

compiler/rustc_codegen_llvm/src/debuginfo/metadata/enums/native.rs

@@ -373,7 +373,7 @@ fn build_discr_member_di_node<'ll, 'tcx>(
                 file,
                 UNKNOWN_LINE_NUMBER,
                 layout,
-                enum_or_coroutine_type_and_layout.fields.offset(tag_field),
+                enum_or_coroutine_type_and_layout.fields.offset(tag_field.as_usize()),
                 DIFlags::FlagArtificial,
                 ty,
             ))

compiler/rustc_codegen_llvm/src/debuginfo/mod.rs

@@ -147,6 +147,12 @@ pub(crate) fn finalize(cx: &CodegenCx<'_, '_>) {
     }
 }
 
+impl<'ll> Builder<'_, 'll, '_> {
+    pub(crate) fn get_dbg_loc(&self) -> Option<&'ll DILocation> {
+        unsafe { llvm::LLVMGetCurrentDebugLocation2(self.llbuilder) }
+    }
+}
+
 impl<'ll> DebugInfoBuilderMethods for Builder<'_, 'll, '_> {
     // FIXME(eddyb) find a common convention for all of the debuginfo-related
     // names (choose between `dbg`, `debug`, `debuginfo`, `debug_info` etc.).
@@ -209,10 +215,6 @@ impl<'ll> DebugInfoBuilderMethods for Builder<'_, 'll, '_> {
         }
     }
 
-    fn get_dbg_loc(&self) -> Option<&'ll DILocation> {
-        unsafe { llvm::LLVMGetCurrentDebugLocation2(self.llbuilder) }
-    }
-
     fn insert_reference_to_gdb_debug_scripts_section_global(&mut self) {
         gdb::insert_reference_to_gdb_debug_scripts_section_global(self)
     }

compiler/rustc_codegen_llvm/src/intrinsic.rs

@@ -636,13 +636,6 @@ impl<'ll, 'tcx> IntrinsicCallBuilderMethods<'tcx> for Builder<'_, 'll, 'tcx> {
         }
     }
 
-    fn type_test(&mut self, pointer: Self::Value, typeid: Self::Metadata) -> Self::Value {
-        // Test the called operand using llvm.type.test intrinsic. The LowerTypeTests link-time
-        // optimization pass replaces calls to this intrinsic with code to test type membership.
-        let typeid = self.get_metadata_value(typeid);
-        self.call_intrinsic("llvm.type.test", &[pointer, typeid])
-    }
-
     fn type_checked_load(
         &mut self,
         llvtable: &'ll Value,

compiler/rustc_codegen_llvm/src/llvm_util.rs

@@ -282,6 +282,14 @@ pub(crate) fn to_llvm_features<'a>(sess: &Session, s: &'a str) -> Option<LLVMFea
         }
         // Filter out features that are not supported by the current LLVM version
         ("riscv32" | "riscv64", "zacas") if get_version().0 < 20 => None,
+        (
+            "s390x",
+            "message-security-assist-extension12"
+            | "concurrent-functions"
+            | "miscellaneous-extensions-4"
+            | "vector-enhancements-3"
+            | "vector-packed-decimal-enhancement-3",
+        ) if get_version().0 < 20 => None,
         // Enable the evex512 target feature if an avx512 target feature is enabled.
         ("x86", s) if s.starts_with("avx512") => Some(LLVMFeature::with_dependencies(
             s,

compiler/rustc_codegen_ssa/messages.ftl

@@ -8,8 +8,6 @@ codegen_ssa_aix_strip_not_used = using host's `strip` binary to cross-compile to
 
 codegen_ssa_archive_build_failure = failed to build archive at `{$path}`: {$error}
 
-codegen_ssa_atomic_compare_exchange = Atomic compare-exchange intrinsic missing failure memory ordering
-
 codegen_ssa_autodiff_without_lto = using the autodiff feature requires using fat-lto
 
 codegen_ssa_bare_instruction_set = `#[instruction_set]` requires an argument
@@ -206,8 +204,6 @@ codegen_ssa_missing_cpp_build_tool_component = or a necessary component may be m
 
 codegen_ssa_missing_features = add the missing features in a `target_feature` attribute
 
-codegen_ssa_missing_memory_ordering = Atomic intrinsic missing memory ordering
-
 codegen_ssa_missing_query_depgraph =
     found CGU-reuse attribute but `-Zquery-dep-graph` was not specified
 
@@ -374,10 +370,6 @@ codegen_ssa_unexpected_parameter_name = unexpected parameter name
 codegen_ssa_unknown_archive_kind =
     Don't know how to build archive of type: {$kind}
 
-codegen_ssa_unknown_atomic_operation = unknown atomic operation
-
-codegen_ssa_unknown_atomic_ordering = unknown ordering in atomic intrinsic
-
 codegen_ssa_unknown_reuse_kind = unknown cgu-reuse-kind `{$kind}` specified
 
 codegen_ssa_unsupported_instruction_set = target does not support `#[instruction_set]`

compiler/rustc_codegen_ssa/src/back/link.rs

@@ -1961,7 +1961,7 @@ fn add_post_link_args(cmd: &mut dyn Linker, sess: &Session, flavor: LinkerFlavor
 /// This method creates a synthetic object file, which contains undefined references to all symbols
 /// that are necessary for the linking. They are only present in symbol table but not actually
 /// used in any sections, so the linker will therefore pick relevant rlibs for linking, but
-/// unused `#[no_mangle]` or `#[used]` can still be discard by GC sections.
+/// unused `#[no_mangle]` or `#[used(compiler)]` can still be discard by GC sections.
 ///
 /// There's a few internal crates in the standard library (aka libcore and
 /// libstd) which actually have a circular dependence upon one another. This
@@ -1995,7 +1995,8 @@ fn add_linked_symbol_object(
 
     if file.format() == object::BinaryFormat::MachO {
         // Divide up the sections into sub-sections via symbols for dead code stripping.
-        // Without this flag, unused `#[no_mangle]` or `#[used]` cannot be discard on MachO targets.
+        // Without this flag, unused `#[no_mangle]` or `#[used(compiler)]` cannot be
+        // discard on MachO targets.
         file.set_subsections_via_symbols();
     }
 

compiler/rustc_codegen_ssa/src/back/symbol_export.rs

@@ -1,5 +1,6 @@
 use std::collections::hash_map::Entry::*;
 
+use rustc_abi::{CanonAbi, X86Call};
 use rustc_ast::expand::allocator::{ALLOCATOR_METHODS, NO_ALLOC_SHIM_IS_UNSTABLE, global_fn_name};
 use rustc_data_structures::unord::UnordMap;
 use rustc_hir::def::DefKind;
@@ -14,7 +15,6 @@ use rustc_middle::ty::{self, GenericArgKind, GenericArgsRef, Instance, SymbolNam
 use rustc_middle::util::Providers;
 use rustc_session::config::{CrateType, OomStrategy};
 use rustc_symbol_mangling::mangle_internal_symbol;
-use rustc_target::callconv::Conv;
 use rustc_target::spec::{SanitizerSet, TlsModel};
 use tracing::debug;
 
@@ -652,7 +652,7 @@ pub(crate) fn symbol_name_for_instance_in_crate<'tcx>(
 fn calling_convention_for_symbol<'tcx>(
     tcx: TyCtxt<'tcx>,
     symbol: ExportedSymbol<'tcx>,
-) -> (Conv, &'tcx [rustc_target::callconv::ArgAbi<'tcx, Ty<'tcx>>]) {
+) -> (CanonAbi, &'tcx [rustc_target::callconv::ArgAbi<'tcx, Ty<'tcx>>]) {
     let instance = match symbol {
         ExportedSymbol::NonGeneric(def_id) | ExportedSymbol::Generic(def_id, _)
             if tcx.is_static(def_id) =>
@@ -683,7 +683,7 @@ fn calling_convention_for_symbol<'tcx>(
         })
         .map(|fnabi| (fnabi.conv, &fnabi.args[..]))
         // FIXME(workingjubilee): why don't we know the convention here?
-        .unwrap_or((Conv::Rust, &[]))
+        .unwrap_or((CanonAbi::Rust, &[]))
 }
 
 /// This is the symbol name of the given instance as seen by the linker.
@@ -717,14 +717,14 @@ pub(crate) fn linking_symbol_name_for_instance_in_crate<'tcx>(
         _ => return undecorated,
     };
 
-    let (conv, args) = calling_convention_for_symbol(tcx, symbol);
+    let (callconv, args) = calling_convention_for_symbol(tcx, symbol);
 
     // Decorate symbols with prefixes, suffixes and total number of bytes of arguments.
     // Reference: https://docs.microsoft.com/en-us/cpp/build/reference/decorated-names?view=msvc-170
-    let (prefix, suffix) = match conv {
-        Conv::X86Fastcall => ("@", "@"),
-        Conv::X86Stdcall => ("_", "@"),
-        Conv::X86VectorCall => ("", "@@"),
+    let (prefix, suffix) = match callconv {
+        CanonAbi::X86(X86Call::Fastcall) => ("@", "@"),
+        CanonAbi::X86(X86Call::Stdcall) => ("_", "@"),
+        CanonAbi::X86(X86Call::Vectorcall) => ("", "@@"),
         _ => {
             if let Some(prefix) = prefix {
                 undecorated.insert(0, prefix);
@@ -758,9 +758,9 @@ pub(crate) fn extend_exported_symbols<'tcx>(
     symbol: ExportedSymbol<'tcx>,
     instantiating_crate: CrateNum,
 ) {
-    let (conv, _) = calling_convention_for_symbol(tcx, symbol);
+    let (callconv, _) = calling_convention_for_symbol(tcx, symbol);
 
-    if conv != Conv::GpuKernel || tcx.sess.target.os != "amdhsa" {
+    if callconv != CanonAbi::GpuKernel || tcx.sess.target.os != "amdhsa" {
         return;
     }
 

compiler/rustc_codegen_ssa/src/base.rs

@@ -561,7 +561,7 @@ pub fn maybe_create_entry_wrapper<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
 
         let EntryFnType::Main { sigpipe } = entry_type;
         let (start_fn, start_ty, args, instance) = {
-            let start_def_id = cx.tcx().require_lang_item(LangItem::Start, None);
+            let start_def_id = cx.tcx().require_lang_item(LangItem::Start, DUMMY_SP);
             let start_instance = ty::Instance::expect_resolve(
                 cx.tcx(),
                 cx.typing_env(),

compiler/rustc_codegen_ssa/src/codegen_attrs.rs

@@ -195,35 +195,10 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
                         tcx.dcx().emit_err(errors::ExpectedUsedSymbol { span: attr.span() });
                     }
                     None => {
-                        // Unfortunately, unconditionally using `llvm.used` causes
-                        // issues in handling `.init_array` with the gold linker,
-                        // but using `llvm.compiler.used` caused a nontrivial amount
-                        // of unintentional ecosystem breakage -- particularly on
-                        // Mach-O targets.
-                        //
-                        // As a result, we emit `llvm.compiler.used` only on ELF
-                        // targets. This is somewhat ad-hoc, but actually follows
-                        // our pre-LLVM 13 behavior (prior to the ecosystem
-                        // breakage), and seems to match `clang`'s behavior as well
-                        // (both before and after LLVM 13), possibly because they
-                        // have similar compatibility concerns to us. See
-                        // https://github.com/rust-lang/rust/issues/47384#issuecomment-1019080146
-                        // and following comments for some discussion of this, as
-                        // well as the comments in `rustc_codegen_llvm` where these
-                        // flags are handled.
-                        //
-                        // Anyway, to be clear: this is still up in the air
-                        // somewhat, and is subject to change in the future (which
-                        // is a good thing, because this would ideally be a bit
-                        // more firmed up).
-                        let is_like_elf = !(tcx.sess.target.is_like_darwin
-                            || tcx.sess.target.is_like_windows
-                            || tcx.sess.target.is_like_wasm);
-                        codegen_fn_attrs.flags |= if is_like_elf {
-                            CodegenFnAttrFlags::USED_COMPILER
-                        } else {
-                            CodegenFnAttrFlags::USED_LINKER
-                        };
+                        // Unconditionally using `llvm.used` causes issues in handling
+                        // `.init_array` with the gold linker. Luckily gold has been
+                        // deprecated with GCC 15 and rustc now warns about using gold.
+                        codegen_fn_attrs.flags |= CodegenFnAttrFlags::USED_LINKER
                     }
                 }
             }

compiler/rustc_codegen_ssa/src/common.rs

@@ -110,7 +110,7 @@ mod temp_stable_hash_impls {
 
 pub(crate) fn build_langcall<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
     bx: &Bx,
-    span: Option<Span>,
+    span: Span,
     li: LangItem,
 ) -> (Bx::FnAbiOfResult, Bx::Value, Instance<'tcx>) {
     let tcx = bx.tcx();

compiler/rustc_codegen_ssa/src/errors.rs

@@ -796,22 +796,6 @@ pub(crate) struct ShuffleIndicesEvaluation {
     pub span: Span,
 }
 
-#[derive(Diagnostic)]
-#[diag(codegen_ssa_missing_memory_ordering)]
-pub(crate) struct MissingMemoryOrdering;
-
-#[derive(Diagnostic)]
-#[diag(codegen_ssa_unknown_atomic_ordering)]
-pub(crate) struct UnknownAtomicOrdering;
-
-#[derive(Diagnostic)]
-#[diag(codegen_ssa_atomic_compare_exchange)]
-pub(crate) struct AtomicCompareExchange;
-
-#[derive(Diagnostic)]
-#[diag(codegen_ssa_unknown_atomic_operation)]
-pub(crate) struct UnknownAtomicOperation;
-
 #[derive(Diagnostic)]
 pub enum InvalidMonomorphization<'tcx> {
     #[diag(codegen_ssa_invalid_monomorphization_basic_integer_type, code = E0511)]

compiler/rustc_codegen_ssa/src/mir/block.rs

@@ -783,7 +783,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
             }
         };
 
-        let (fn_abi, llfn, instance) = common::build_langcall(bx, Some(span), lang_item);
+        let (fn_abi, llfn, instance) = common::build_langcall(bx, span, lang_item);
 
         // Codegen the actual panic invoke/call.
         let merging_succ =
@@ -803,7 +803,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         self.set_debug_loc(bx, terminator.source_info);
 
         // Obtain the panic entry point.
-        let (fn_abi, llfn, instance) = common::build_langcall(bx, Some(span), reason.lang_item());
+        let (fn_abi, llfn, instance) = common::build_langcall(bx, span, reason.lang_item());
 
         // Codegen the actual panic invoke/call.
         let merging_succ = helper.do_call(
@@ -871,7 +871,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
 
         // Obtain the panic entry point.
         let (fn_abi, llfn, instance) =
-            common::build_langcall(bx, Some(source_info.span), LangItem::PanicNounwind);
+            common::build_langcall(bx, source_info.span, LangItem::PanicNounwind);
 
         // Codegen the actual panic invoke/call.
         Some(helper.do_call(
@@ -1077,7 +1077,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                             let (idx, _) = op.layout.non_1zst_field(bx).expect(
                                 "not exactly one non-1-ZST field in a `DispatchFromDyn` type",
                             );
-                            op = op.extract_field(self, bx, idx);
+                            op = op.extract_field(self, bx, idx.as_usize());
                         }
 
                         // Now that we have `*dyn Trait` or `&dyn Trait`, split it up into its
@@ -1109,7 +1109,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                             let (idx, _) = op.layout.non_1zst_field(bx).expect(
                                 "not exactly one non-1-ZST field in a `DispatchFromDyn` type",
                             );
-                            op = op.extract_field(self, bx, idx);
+                            op = op.extract_field(self, bx, idx.as_usize());
                         }
 
                         // Make sure that we've actually unwrapped the rcvr down
@@ -1830,7 +1830,8 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
 
         self.set_debug_loc(&mut bx, mir::SourceInfo::outermost(self.mir.span));
 
-        let (fn_abi, fn_ptr, instance) = common::build_langcall(&bx, None, reason.lang_item());
+        let (fn_abi, fn_ptr, instance) =
+            common::build_langcall(&bx, self.mir.span, reason.lang_item());
         if is_call_from_compiler_builtins_to_upstream_monomorphization(bx.tcx(), instance) {
             bx.abort();
         } else {

compiler/rustc_codegen_ssa/src/mir/intrinsic.rs

@@ -8,9 +8,10 @@ use rustc_span::sym;
 use super::FunctionCx;
 use super::operand::OperandRef;
 use super::place::PlaceRef;
+use crate::common::{AtomicRmwBinOp, SynchronizationScope};
 use crate::errors::InvalidMonomorphization;
 use crate::traits::*;
-use crate::{MemFlags, errors, meth, size_of_val};
+use crate::{MemFlags, meth, size_of_val};
 
 fn copy_intrinsic<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
     bx: &mut Bx,
@@ -62,7 +63,6 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
         let span = source_info.span;
 
         let name = bx.tcx().item_name(instance.def_id());
-        let name_str = name.as_str();
         let fn_args = instance.args;
 
         // If we're swapping something that's *not* an `OperandValue::Ref`,
@@ -89,14 +89,13 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
             }
         }
 
-        let ret_llval = |bx: &mut Bx, llval| {
-            if result.layout.ty.is_bool() {
-                let val = bx.from_immediate(llval);
-                bx.store_to_place(val, result.val);
-            } else if !result.layout.ty.is_unit() {
-                bx.store_to_place(llval, result.val);
-            }
-            Ok(())
+        let invalid_monomorphization_int_type = |ty| {
+            bx.tcx().dcx().emit_err(InvalidMonomorphization::BasicIntegerType { span, name, ty });
+        };
+
+        let parse_atomic_ordering = |ord: ty::Value<'tcx>| {
+            let discr = ord.valtree.unwrap_branch()[0].unwrap_leaf();
+            discr.to_atomic_ordering()
         };
 
         let llval = match name {
@@ -336,183 +335,144 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                 }
             }
 
-            // This requires that atomic intrinsics follow a specific naming pattern:
-            // "atomic_<operation>[_<ordering>]"
-            name if let Some(atomic) = name_str.strip_prefix("atomic_") => {
-                use rustc_middle::ty::AtomicOrdering::*;
-
-                use crate::common::{AtomicRmwBinOp, SynchronizationScope};
-
-                let invalid_monomorphization = |ty| {
-                    bx.tcx().dcx().emit_err(InvalidMonomorphization::BasicIntegerType {
-                        span,
-                        name,
-                        ty,
-                    });
-                };
-
-                let parse_const_generic_ordering = |ord: ty::Value<'tcx>| {
-                    let discr = ord.valtree.unwrap_branch()[0].unwrap_leaf();
-                    discr.to_atomic_ordering()
-                };
-
-                // Some intrinsics have the ordering already converted to a const generic parameter, we handle those first.
-                match name {
-                    sym::atomic_load => {
-                        let ty = fn_args.type_at(0);
-                        let ordering = fn_args.const_at(1).to_value();
-                        if !(int_type_width_signed(ty, bx.tcx()).is_some() || ty.is_raw_ptr()) {
-                            invalid_monomorphization(ty);
-                            return Ok(());
-                        }
-                        let layout = bx.layout_of(ty);
-                        let source = args[0].immediate();
-                        let llval = bx.atomic_load(
-                            bx.backend_type(layout),
-                            source,
-                            parse_const_generic_ordering(ordering),
-                            layout.size,
-                        );
-
-                        return ret_llval(bx, llval);
-                    }
-
-                    // The rest falls back to below.
-                    _ => {}
+            sym::atomic_load => {
+                let ty = fn_args.type_at(0);
+                if !(int_type_width_signed(ty, bx.tcx()).is_some() || ty.is_raw_ptr()) {
+                    invalid_monomorphization_int_type(ty);
+                    return Ok(());
                 }
-
-                let Some((instruction, ordering)) = atomic.split_once('_') else {
-                    bx.sess().dcx().emit_fatal(errors::MissingMemoryOrdering);
-                };
-
-                let parse_ordering = |bx: &Bx, s| match s {
-                    "relaxed" => Relaxed,
-                    "acquire" => Acquire,
-                    "release" => Release,
-                    "acqrel" => AcqRel,
-                    "seqcst" => SeqCst,
-                    _ => bx.sess().dcx().emit_fatal(errors::UnknownAtomicOrdering),
-                };
-
-                match instruction {
-                    "cxchg" | "cxchgweak" => {
-                        let Some((success, failure)) = ordering.split_once('_') else {
-                            bx.sess().dcx().emit_fatal(errors::AtomicCompareExchange);
-                        };
-                        let ty = fn_args.type_at(0);
-                        if int_type_width_signed(ty, bx.tcx()).is_some() || ty.is_raw_ptr() {
-                            let weak = instruction == "cxchgweak";
-                            let dst = args[0].immediate();
-                            let cmp = args[1].immediate();
-                            let src = args[2].immediate();
-                            let (val, success) = bx.atomic_cmpxchg(
-                                dst,
-                                cmp,
-                                src,
-                                parse_ordering(bx, success),
-                                parse_ordering(bx, failure),
-                                weak,
-                            );
-                            let val = bx.from_immediate(val);
-                            let success = bx.from_immediate(success);
-
-                            let dest = result.project_field(bx, 0);
-                            bx.store_to_place(val, dest.val);
-                            let dest = result.project_field(bx, 1);
-                            bx.store_to_place(success, dest.val);
-                        } else {
-                            invalid_monomorphization(ty);
-                        }
-                        return Ok(());
-                    }
-
-                    "store" => {
-                        let ty = fn_args.type_at(0);
-                        if int_type_width_signed(ty, bx.tcx()).is_some() || ty.is_raw_ptr() {
-                            let size = bx.layout_of(ty).size;
-                            let val = args[1].immediate();
-                            let ptr = args[0].immediate();
-                            bx.atomic_store(val, ptr, parse_ordering(bx, ordering), size);
-                        } else {
-                            invalid_monomorphization(ty);
-                        }
-                        return Ok(());
-                    }
-
-                    "fence" => {
-                        bx.atomic_fence(
-                            parse_ordering(bx, ordering),
-                            SynchronizationScope::CrossThread,
-                        );
-                        return Ok(());
-                    }
-
-                    "singlethreadfence" => {
-                        bx.atomic_fence(
-                            parse_ordering(bx, ordering),
-                            SynchronizationScope::SingleThread,
-                        );
-                        return Ok(());
-                    }
-
-                    // These are all AtomicRMW ops
-                    "max" | "min" => {
-                        let atom_op = if instruction == "max" {
-                            AtomicRmwBinOp::AtomicMax
-                        } else {
-                            AtomicRmwBinOp::AtomicMin
-                        };
-
-                        let ty = fn_args.type_at(0);
-                        if matches!(ty.kind(), ty::Int(_)) {
-                            let ptr = args[0].immediate();
-                            let val = args[1].immediate();
-                            bx.atomic_rmw(atom_op, ptr, val, parse_ordering(bx, ordering))
-                        } else {
-                            invalid_monomorphization(ty);
-                            return Ok(());
-                        }
-                    }
-                    "umax" | "umin" => {
-                        let atom_op = if instruction == "umax" {
-                            AtomicRmwBinOp::AtomicUMax
-                        } else {
-                            AtomicRmwBinOp::AtomicUMin
-                        };
-
-                        let ty = fn_args.type_at(0);
-                        if matches!(ty.kind(), ty::Uint(_)) {
-                            let ptr = args[0].immediate();
-                            let val = args[1].immediate();
-                            bx.atomic_rmw(atom_op, ptr, val, parse_ordering(bx, ordering))
-                        } else {
-                            invalid_monomorphization(ty);
-                            return Ok(());
-                        }
-                    }
-                    op => {
-                        let atom_op = match op {
-                            "xchg" => AtomicRmwBinOp::AtomicXchg,
-                            "xadd" => AtomicRmwBinOp::AtomicAdd,
-                            "xsub" => AtomicRmwBinOp::AtomicSub,
-                            "and" => AtomicRmwBinOp::AtomicAnd,
-                            "nand" => AtomicRmwBinOp::AtomicNand,
-                            "or" => AtomicRmwBinOp::AtomicOr,
-                            "xor" => AtomicRmwBinOp::AtomicXor,
-                            _ => bx.sess().dcx().emit_fatal(errors::UnknownAtomicOperation),
-                        };
-
-                        let ty = fn_args.type_at(0);
-                        if int_type_width_signed(ty, bx.tcx()).is_some() || ty.is_raw_ptr() {
-                            let ptr = args[0].immediate();
-                            let val = args[1].immediate();
-                            bx.atomic_rmw(atom_op, ptr, val, parse_ordering(bx, ordering))
-                        } else {
-                            invalid_monomorphization(ty);
-                            return Ok(());
-                        }
-                    }
+                let ordering = fn_args.const_at(1).to_value();
+                let layout = bx.layout_of(ty);
+                let source = args[0].immediate();
+                bx.atomic_load(
+                    bx.backend_type(layout),
+                    source,
+                    parse_atomic_ordering(ordering),
+                    layout.size,
+                )
+            }
+            sym::atomic_store => {
+                let ty = fn_args.type_at(0);
+                if !(int_type_width_signed(ty, bx.tcx()).is_some() || ty.is_raw_ptr()) {
+                    invalid_monomorphization_int_type(ty);
+                    return Ok(());
                 }
+                let ordering = fn_args.const_at(1).to_value();
+                let size = bx.layout_of(ty).size;
+                let val = args[1].immediate();
+                let ptr = args[0].immediate();
+                bx.atomic_store(val, ptr, parse_atomic_ordering(ordering), size);
+                return Ok(());
+            }
+            sym::atomic_cxchg | sym::atomic_cxchgweak => {
+                let ty = fn_args.type_at(0);
+                if !(int_type_width_signed(ty, bx.tcx()).is_some() || ty.is_raw_ptr()) {
+                    invalid_monomorphization_int_type(ty);
+                    return Ok(());
+                }
+                let succ_ordering = fn_args.const_at(1).to_value();
+                let fail_ordering = fn_args.const_at(2).to_value();
+                let weak = name == sym::atomic_cxchgweak;
+                let dst = args[0].immediate();
+                let cmp = args[1].immediate();
+                let src = args[2].immediate();
+                let (val, success) = bx.atomic_cmpxchg(
+                    dst,
+                    cmp,
+                    src,
+                    parse_atomic_ordering(succ_ordering),
+                    parse_atomic_ordering(fail_ordering),
+                    weak,
+                );
+                let val = bx.from_immediate(val);
+                let success = bx.from_immediate(success);
+
+                let dest = result.project_field(bx, 0);
+                bx.store_to_place(val, dest.val);
+                let dest = result.project_field(bx, 1);
+                bx.store_to_place(success, dest.val);
+
+                return Ok(());
+            }
+            // These are all AtomicRMW ops
+            sym::atomic_max | sym::atomic_min => {
+                let atom_op = if name == sym::atomic_max {
+                    AtomicRmwBinOp::AtomicMax
+                } else {
+                    AtomicRmwBinOp::AtomicMin
+                };
+
+                let ty = fn_args.type_at(0);
+                if matches!(ty.kind(), ty::Int(_)) {
+                    let ordering = fn_args.const_at(1).to_value();
+                    let ptr = args[0].immediate();
+                    let val = args[1].immediate();
+                    bx.atomic_rmw(atom_op, ptr, val, parse_atomic_ordering(ordering))
+                } else {
+                    invalid_monomorphization_int_type(ty);
+                    return Ok(());
+                }
+            }
+            sym::atomic_umax | sym::atomic_umin => {
+                let atom_op = if name == sym::atomic_umax {
+                    AtomicRmwBinOp::AtomicUMax
+                } else {
+                    AtomicRmwBinOp::AtomicUMin
+                };
+
+                let ty = fn_args.type_at(0);
+                if matches!(ty.kind(), ty::Uint(_)) {
+                    let ordering = fn_args.const_at(1).to_value();
+                    let ptr = args[0].immediate();
+                    let val = args[1].immediate();
+                    bx.atomic_rmw(atom_op, ptr, val, parse_atomic_ordering(ordering))
+                } else {
+                    invalid_monomorphization_int_type(ty);
+                    return Ok(());
+                }
+            }
+            sym::atomic_xchg
+            | sym::atomic_xadd
+            | sym::atomic_xsub
+            | sym::atomic_and
+            | sym::atomic_nand
+            | sym::atomic_or
+            | sym::atomic_xor => {
+                let atom_op = match name {
+                    sym::atomic_xchg => AtomicRmwBinOp::AtomicXchg,
+                    sym::atomic_xadd => AtomicRmwBinOp::AtomicAdd,
+                    sym::atomic_xsub => AtomicRmwBinOp::AtomicSub,
+                    sym::atomic_and => AtomicRmwBinOp::AtomicAnd,
+                    sym::atomic_nand => AtomicRmwBinOp::AtomicNand,
+                    sym::atomic_or => AtomicRmwBinOp::AtomicOr,
+                    sym::atomic_xor => AtomicRmwBinOp::AtomicXor,
+                    _ => unreachable!(),
+                };
+
+                let ty = fn_args.type_at(0);
+                if int_type_width_signed(ty, bx.tcx()).is_some() || ty.is_raw_ptr() {
+                    let ordering = fn_args.const_at(1).to_value();
+                    let ptr = args[0].immediate();
+                    let val = args[1].immediate();
+                    bx.atomic_rmw(atom_op, ptr, val, parse_atomic_ordering(ordering))
+                } else {
+                    invalid_monomorphization_int_type(ty);
+                    return Ok(());
+                }
+            }
+            sym::atomic_fence => {
+                let ordering = fn_args.const_at(0).to_value();
+                bx.atomic_fence(parse_atomic_ordering(ordering), SynchronizationScope::CrossThread);
+                return Ok(());
+            }
+
+            sym::atomic_singlethreadfence => {
+                let ordering = fn_args.const_at(0).to_value();
+                bx.atomic_fence(
+                    parse_atomic_ordering(ordering),
+                    SynchronizationScope::SingleThread,
+                );
+                return Ok(());
             }
 
             sym::nontemporal_store => {
@@ -556,7 +516,13 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
             }
         };
 
-        ret_llval(bx, llval)
+        if result.layout.ty.is_bool() {
+            let val = bx.from_immediate(llval);
+            bx.store_to_place(val, result.val);
+        } else if !result.layout.ty.is_unit() {
+            bx.store_to_place(llval, result.val);
+        }
+        Ok(())
     }
 }
 

compiler/rustc_codegen_ssa/src/mir/operand.rs

@@ -45,9 +45,15 @@ pub enum OperandValue<V> {
     Immediate(V),
     /// A pair of immediate LLVM values. Used by wide pointers too.
     ///
-    /// An `OperandValue` *must* be this variant for any type for which
+    /// # Invariants
+    /// - For `Pair(a, b)`, `a` is always at offset 0, but may have `FieldIdx(1..)`
+    /// - `b` is not at offset 0, because `V` is not a 1ZST type.
+    /// - `a` and `b` will have a different FieldIdx, but otherwise `b`'s may be lower
+    ///   or they may not be adjacent, due to arbitrary numbers of 1ZST fields that
+    ///   will not affect the shape of the data which determines if `Pair` will be used.
+    /// - An `OperandValue` *must* be this variant for any type for which
     /// [`LayoutTypeCodegenMethods::is_backend_scalar_pair`] returns `true`.
-    /// The backend values in this variant must be the *immediate* backend types,
+    /// - The backend values in this variant must be the *immediate* backend types,
     /// as returned by [`LayoutTypeCodegenMethods::scalar_pair_element_backend_type`]
     /// with `immediate: true`.
     Pair(V, V),
@@ -462,10 +468,10 @@ impl<'a, 'tcx, V: CodegenObject> OperandRef<'tcx, V> {
         let tag_op = match self.val {
             OperandValue::ZeroSized => bug!(),
             OperandValue::Immediate(_) | OperandValue::Pair(_, _) => {
-                self.extract_field(fx, bx, tag_field)
+                self.extract_field(fx, bx, tag_field.as_usize())
             }
             OperandValue::Ref(place) => {
-                let tag = place.with_type(self.layout).project_field(bx, tag_field);
+                let tag = place.with_type(self.layout).project_field(bx, tag_field.as_usize());
                 bx.load_operand(tag)
             }
         };

compiler/rustc_codegen_ssa/src/mir/place.rs

@@ -250,7 +250,7 @@ impl<'a, 'tcx, V: CodegenObject> PlaceRef<'tcx, V> {
             Variants::Single { index } => assert_eq!(index, variant_index),
 
             Variants::Multiple { tag_encoding: TagEncoding::Direct, tag_field, .. } => {
-                let ptr = self.project_field(bx, tag_field);
+                let ptr = self.project_field(bx, tag_field.as_usize());
                 let to =
                     self.layout.ty.discriminant_for_variant(bx.tcx(), variant_index).unwrap().val;
                 bx.store_to_place(
@@ -265,7 +265,7 @@ impl<'a, 'tcx, V: CodegenObject> PlaceRef<'tcx, V> {
                 ..
             } => {
                 if variant_index != untagged_variant {
-                    let niche = self.project_field(bx, tag_field);
+                    let niche = self.project_field(bx, tag_field.as_usize());
                     let niche_llty = bx.cx().immediate_backend_type(niche.layout);
                     let BackendRepr::Scalar(scalar) = niche.layout.backend_repr else {
                         bug!("expected a scalar placeref for the niche");

compiler/rustc_codegen_ssa/src/size_of_val.rs

@@ -5,6 +5,7 @@ use rustc_hir::LangItem;
 use rustc_middle::bug;
 use rustc_middle::ty::print::{with_no_trimmed_paths, with_no_visible_paths};
 use rustc_middle::ty::{self, Ty};
+use rustc_span::DUMMY_SP;
 use tracing::{debug, trace};
 
 use crate::common::IntPredicate;
@@ -62,7 +63,7 @@ pub fn size_and_align_of_dst<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
 
             // Obtain the panic entry point.
             let (fn_abi, llfn, _instance) =
-                common::build_langcall(bx, None, LangItem::PanicNounwind);
+                common::build_langcall(bx, DUMMY_SP, LangItem::PanicNounwind);
 
             // Generate the call. Cannot use `do_call` since we don't have a MIR terminator so we
             // can't create a `TerminationCodegenHelper`. (But we are in good company, this code is

compiler/rustc_codegen_ssa/src/traits/debuginfo.rs

@@ -81,7 +81,6 @@ pub trait DebugInfoBuilderMethods: BackendTypes {
     );
     fn set_dbg_loc(&mut self, dbg_loc: Self::DILocation);
     fn clear_dbg_loc(&mut self);
-    fn get_dbg_loc(&self) -> Option<Self::DILocation>;
     fn insert_reference_to_gdb_debug_scripts_section_global(&mut self);
     fn set_var_name(&mut self, value: Self::Value, name: &str);
 }

compiler/rustc_codegen_ssa/src/traits/intrinsic.rs

@@ -22,8 +22,6 @@ pub trait IntrinsicCallBuilderMethods<'tcx>: BackendTypes {
     fn abort(&mut self);
     fn assume(&mut self, val: Self::Value);
     fn expect(&mut self, cond: Self::Value, expected: bool) -> Self::Value;
-    /// Trait method used to test whether a given pointer is associated with a type identifier.
-    fn type_test(&mut self, pointer: Self::Value, typeid: Self::Metadata) -> Self::Value;
     /// Trait method used to load a function while testing if it is associated with a type
     /// identifier.
     fn type_checked_load(

compiler/rustc_const_eval/messages.ftl

@@ -88,11 +88,9 @@ const_eval_division_overflow =
 const_eval_dyn_call_not_a_method =
     `dyn` call trying to call something that is not a method
 
-const_eval_error = {$error_kind ->
-    [static] could not evaluate static initializer
-    [const] evaluation of constant value failed
-    [const_with_path] evaluation of `{$instance}` failed
-    *[other] {""}
+const_eval_error = evaluation of `{$instance}` failed {$num_frames ->
+    [0] here
+    *[other] inside this call
 }
 
 const_eval_exact_div_has_remainder =
@@ -118,7 +116,7 @@ const_eval_frame_note_inner = inside {$where_ ->
 const_eval_frame_note_last = the failure occurred here
 
 const_eval_incompatible_calling_conventions =
-    calling a function with calling convention {$callee_conv} using calling convention {$caller_conv}
+    calling a function with calling convention "{$callee_conv}" using calling convention "{$caller_conv}"
 
 const_eval_incompatible_return_types =
     calling a function with return type {$callee_ty} passing return place of type {$caller_ty}

compiler/rustc_const_eval/src/check_consts/check.rs

@@ -589,12 +589,7 @@ impl<'tcx> Visitor<'tcx> for Checker<'_, 'tcx> {
 
             Rvalue::Aggregate(kind, ..) => {
                 if let AggregateKind::Coroutine(def_id, ..) = kind.as_ref()
-                    && let Some(
-                        coroutine_kind @ hir::CoroutineKind::Desugared(
-                            hir::CoroutineDesugaring::Async,
-                            _,
-                        ),
-                    ) = self.tcx.coroutine_kind(def_id)
+                    && let Some(coroutine_kind) = self.tcx.coroutine_kind(def_id)
                 {
                     self.check_op(ops::Coroutine(coroutine_kind));
                 }

compiler/rustc_const_eval/src/check_consts/ops.rs

@@ -345,11 +345,7 @@ fn build_error_for_const_call<'tcx>(
                 non_or_conditionally,
             });
 
-            note_trait_if_possible(
-                &mut err,
-                self_ty,
-                tcx.require_lang_item(LangItem::Deref, Some(span)),
-            );
+            note_trait_if_possible(&mut err, self_ty, tcx.require_lang_item(LangItem::Deref, span));
             err
         }
         _ if tcx.opt_parent(callee) == tcx.get_diagnostic_item(sym::FmtArgumentsNew) => {
@@ -486,24 +482,25 @@ impl<'tcx> NonConstOp<'tcx> for IntrinsicUnstable {
 pub(crate) struct Coroutine(pub hir::CoroutineKind);
 impl<'tcx> NonConstOp<'tcx> for Coroutine {
     fn status_in_item(&self, _: &ConstCx<'_, 'tcx>) -> Status {
-        if let hir::CoroutineKind::Desugared(
-            hir::CoroutineDesugaring::Async,
-            hir::CoroutineSource::Block,
-        ) = self.0
-        {
-            Status::Unstable {
+        match self.0 {
+            hir::CoroutineKind::Desugared(
+                hir::CoroutineDesugaring::Async,
+                hir::CoroutineSource::Block,
+            )
+            // FIXME(coroutines): eventually we want to gate const coroutine coroutines behind a
+            // different feature.
+            | hir::CoroutineKind::Coroutine(_) => Status::Unstable {
                 gate: sym::const_async_blocks,
                 gate_already_checked: false,
                 safe_to_expose_on_stable: false,
                 is_function_call: false,
-            }
-        } else {
-            Status::Forbidden
+            },
+            _ => Status::Forbidden,
         }
     }
 
     fn build_error(&self, ccx: &ConstCx<'_, 'tcx>, span: Span) -> Diag<'tcx> {
-        let msg = format!("{:#}s are not allowed in {}s", self.0, ccx.const_kind());
+        let msg = format!("{} are not allowed in {}s", self.0.to_plural_string(), ccx.const_kind());
         if let Status::Unstable { gate, .. } = self.status_in_item(ccx) {
             ccx.tcx.sess.create_feature_err(errors::UnallowedOpInConstContext { span, msg }, gate)
         } else {

compiler/rustc_const_eval/src/check_consts/qualifs.rs

@@ -99,7 +99,7 @@ impl Qualif for HasMutInterior {
         // requires borrowck, which in turn will invoke mir_const_qualifs again, causing a cycle error.
         // Instead we invoke an obligation context manually, and provide the opaque type inference settings
         // that allow the trait solver to just error out instead of cycling.
-        let freeze_def_id = cx.tcx.require_lang_item(LangItem::Freeze, Some(cx.body.span));
+        let freeze_def_id = cx.tcx.require_lang_item(LangItem::Freeze, cx.body.span);
         // FIXME(#132279): Once we've got a typing mode which reveals opaque types using the HIR
         // typeck results without causing query cycles, we should use this here instead of defining
         // opaque types.
@@ -180,7 +180,7 @@ impl Qualif for NeedsNonConstDrop {
         // that the components of this type are also `~const Destruct`. This
         // amounts to verifying that there are no values in this ADT that may have
         // a non-const drop.
-        let destruct_def_id = cx.tcx.require_lang_item(LangItem::Destruct, Some(cx.body.span));
+        let destruct_def_id = cx.tcx.require_lang_item(LangItem::Destruct, cx.body.span);
         let (infcx, param_env) = cx.tcx.infer_ctxt().build_with_typing_env(cx.typing_env);
         let ocx = ObligationCtxt::new(&infcx);
         ocx.register_obligation(Obligation::new(

compiler/rustc_const_eval/src/const_eval/error.rs

@@ -1,6 +1,6 @@
 use std::mem;
 
-use rustc_errors::{DiagArgName, DiagArgValue, DiagMessage, Diagnostic, IntoDiagArg};
+use rustc_errors::{Diag, DiagArgName, DiagArgValue, DiagMessage, IntoDiagArg};
 use rustc_middle::mir::AssertKind;
 use rustc_middle::mir::interpret::{Provenance, ReportedErrorInfo};
 use rustc_middle::query::TyCtxtAt;
@@ -131,10 +131,10 @@ pub fn get_span_and_frames<'tcx>(
 
 /// Create a diagnostic for a const eval error.
 ///
-/// This will use the `mk` function for creating the error which will get passed labels according to
-/// the `InterpError` and the span and a stacktrace of current execution according to
-/// `get_span_and_frames`.
-pub(super) fn report<'tcx, C, F, E>(
+/// This will use the `mk` function for adding more information to the error.
+/// You can use it to add a stacktrace of current execution according to
+/// `get_span_and_frames` or just give context on where the const eval error happened.
+pub(super) fn report<'tcx, C, F>(
     tcx: TyCtxt<'tcx>,
     error: InterpErrorKind<'tcx>,
     span: Span,
@@ -143,8 +143,7 @@ pub(super) fn report<'tcx, C, F, E>(
 ) -> ErrorHandled
 where
     C: FnOnce() -> (Span, Vec<FrameNote>),
-    F: FnOnce(Span, Vec<FrameNote>) -> E,
-    E: Diagnostic<'tcx>,
+    F: FnOnce(&mut Diag<'_>, Span, Vec<FrameNote>),
 {
     // Special handling for certain errors
     match error {
@@ -163,8 +162,7 @@ where
         _ => {
             let (our_span, frames) = get_span_and_frames();
             let span = span.substitute_dummy(our_span);
-            let err = mk(span, frames);
-            let mut err = tcx.dcx().create_err(err);
+            let mut err = tcx.dcx().struct_span_err(our_span, error.diagnostic_message());
             // We allow invalid programs in infallible promoteds since invalid layouts can occur
             // anyway (e.g. due to size overflow). And we allow OOM as that can happen any time.
             let allowed_in_infallible = matches!(
@@ -172,11 +170,9 @@ where
                 InterpErrorKind::ResourceExhaustion(_) | InterpErrorKind::InvalidProgram(_)
             );
 
-            let msg = error.diagnostic_message();
             error.add_args(&mut err);
 
-            // Use *our* span to label the interp error
-            err.span_label(our_span, msg);
+            mk(&mut err, span, frames);
             let g = err.emit();
             let reported = if allowed_in_infallible {
                 ReportedErrorInfo::allowed_in_infallible(g)

compiler/rustc_const_eval/src/const_eval/eval_queries.rs

@@ -2,6 +2,7 @@ use std::sync::atomic::Ordering::Relaxed;
 
 use either::{Left, Right};
 use rustc_abi::{self as abi, BackendRepr};
+use rustc_errors::E0080;
 use rustc_hir::def::DefKind;
 use rustc_middle::mir::interpret::{AllocId, ErrorHandled, InterpErrorInfo, ReportedErrorInfo};
 use rustc_middle::mir::{self, ConstAlloc, ConstValue};
@@ -290,12 +291,18 @@ pub fn eval_to_const_value_raw_provider<'tcx>(
             |error| {
                 let span = tcx.def_span(def_id);
 
+                // FIXME(oli-obk): why don't we have any tests for this code path?
                 super::report(
                     tcx,
                     error.into_kind(),
                     span,
                     || (span, vec![]),
-                    |span, _| errors::NullaryIntrinsicError { span },
+                    |diag, span, _| {
+                        diag.span_label(
+                            span,
+                            crate::fluent_generated::const_eval_nullary_intrinsic_fail,
+                        );
+                    },
                 )
             },
         );
@@ -423,31 +430,24 @@ fn report_eval_error<'tcx>(
     let (error, backtrace) = error.into_parts();
     backtrace.print_backtrace();
 
-    let (kind, instance) = if ecx.tcx.is_static(cid.instance.def_id()) {
-        ("static", String::new())
-    } else {
-        // If the current item has generics, we'd like to enrich the message with the
-        // instance and its args: to show the actual compile-time values, in addition to
-        // the expression, leading to the const eval error.
-        let instance = &cid.instance;
-        if !instance.args.is_empty() {
-            let instance = with_no_trimmed_paths!(instance.to_string());
-            ("const_with_path", instance)
-        } else {
-            ("const", String::new())
-        }
-    };
+    let instance = with_no_trimmed_paths!(cid.instance.to_string());
 
     super::report(
         *ecx.tcx,
         error,
         DUMMY_SP,
         || super::get_span_and_frames(ecx.tcx, ecx.stack()),
-        |span, frames| errors::ConstEvalError {
-            span,
-            error_kind: kind,
-            instance,
-            frame_notes: frames,
+        |diag, span, frames| {
+            let num_frames = frames.len();
+            // FIXME(oli-obk): figure out how to use structured diagnostics again.
+            diag.code(E0080);
+            diag.span_label(span, crate::fluent_generated::const_eval_error);
+            for frame in frames {
+                diag.subdiagnostic(frame);
+            }
+            // Add after the frame rendering above, as it adds its own `instance` args.
+            diag.arg("instance", instance);
+            diag.arg("num_frames", num_frames);
         },
     )
 }
@@ -477,6 +477,15 @@ fn report_validation_error<'tcx>(
         error,
         DUMMY_SP,
         || crate::const_eval::get_span_and_frames(ecx.tcx, ecx.stack()),
-        move |span, frames| errors::ValidationFailure { span, ub_note: (), frames, raw_bytes },
+        move |diag, span, frames| {
+            // FIXME(oli-obk): figure out how to use structured diagnostics again.
+            diag.code(E0080);
+            diag.span_label(span, crate::fluent_generated::const_eval_validation_failure);
+            diag.note(crate::fluent_generated::const_eval_validation_failure_note);
+            for frame in frames {
+                diag.subdiagnostic(frame);
+            }
+            diag.subdiagnostic(raw_bytes);
+        },
     )
 }

compiler/rustc_const_eval/src/const_eval/machine.rs

@@ -249,7 +249,7 @@ impl<'tcx> CompileTimeInterpCx<'tcx> {
             return Err(ConstEvalErrKind::Panic { msg, file, line, col }).into();
         } else if self.tcx.is_lang_item(def_id, LangItem::PanicFmt) {
             // For panic_fmt, call const_panic_fmt instead.
-            let const_def_id = self.tcx.require_lang_item(LangItem::ConstPanicFmt, None);
+            let const_def_id = self.tcx.require_lang_item(LangItem::ConstPanicFmt, self.tcx.span);
             let new_instance = ty::Instance::expect_resolve(
                 *self.tcx,
                 self.typing_env(),

compiler/rustc_const_eval/src/const_eval/mod.rs

@@ -1,6 +1,6 @@
 // Not in interpret to make sure we do not use private implementation details
 
-use rustc_abi::VariantIdx;
+use rustc_abi::{FieldIdx, VariantIdx};
 use rustc_middle::query::Key;
 use rustc_middle::ty::layout::LayoutOf;
 use rustc_middle::ty::{self, Ty, TyCtxt};
@@ -60,7 +60,7 @@ pub(crate) fn try_destructure_mir_constant_for_user_output<'tcx>(
 
     let fields_iter = (0..field_count)
         .map(|i| {
-            let field_op = ecx.project_field(&down, i).discard_err()?;
+            let field_op = ecx.project_field(&down, FieldIdx::from_usize(i)).discard_err()?;
             let val = op_to_const(&ecx, &field_op, /* for diagnostics */ true);
             Some((val, field_op.layout.ty))
         })

compiler/rustc_const_eval/src/const_eval/valtrees.rs

@@ -1,4 +1,4 @@
-use rustc_abi::{BackendRepr, VariantIdx};
+use rustc_abi::{BackendRepr, FieldIdx, VariantIdx};
 use rustc_data_structures::stack::ensure_sufficient_stack;
 use rustc_middle::mir::interpret::{EvalToValTreeResult, GlobalId, ReportedErrorInfo};
 use rustc_middle::ty::layout::{LayoutCx, LayoutOf, TyAndLayout};
@@ -40,7 +40,7 @@ fn branches<'tcx>(
     }
 
     for i in 0..field_count {
-        let field = ecx.project_field(&place, i).unwrap();
+        let field = ecx.project_field(&place, FieldIdx::from_usize(i)).unwrap();
         let valtree = const_to_valtree_inner(ecx, &field, num_nodes)?;
         branches.push(valtree);
     }
@@ -437,7 +437,7 @@ fn valtree_into_mplace<'tcx>(
                     ty::Str | ty::Slice(_) | ty::Array(..) => {
                         ecx.project_index(place, i as u64).unwrap()
                     }
-                    _ => ecx.project_field(&place_adjusted, i).unwrap(),
+                    _ => ecx.project_field(&place_adjusted, FieldIdx::from_usize(i)).unwrap(),
                 };
 
                 debug!(?place_inner);

compiler/rustc_const_eval/src/errors.rs

@@ -439,38 +439,6 @@ pub struct LiveDrop<'tcx> {
     pub dropped_at: Span,
 }
 
-#[derive(Diagnostic)]
-#[diag(const_eval_error, code = E0080)]
-pub struct ConstEvalError {
-    #[primary_span]
-    pub span: Span,
-    /// One of "const", "const_with_path", and "static"
-    pub error_kind: &'static str,
-    pub instance: String,
-    #[subdiagnostic]
-    pub frame_notes: Vec<FrameNote>,
-}
-
-#[derive(Diagnostic)]
-#[diag(const_eval_nullary_intrinsic_fail)]
-pub struct NullaryIntrinsicError {
-    #[primary_span]
-    pub span: Span,
-}
-
-#[derive(Diagnostic)]
-#[diag(const_eval_validation_failure, code = E0080)]
-pub struct ValidationFailure {
-    #[primary_span]
-    pub span: Span,
-    #[note(const_eval_validation_failure_note)]
-    pub ub_note: (),
-    #[subdiagnostic]
-    pub frames: Vec<FrameNote>,
-    #[subdiagnostic]
-    pub raw_bytes: RawBytesNote,
-}
-
 pub trait ReportErrorExt {
     /// Returns the diagnostic message for this error.
     fn diagnostic_message(&self) -> DiagMessage;

compiler/rustc_const_eval/src/interpret/call.rs

@@ -62,7 +62,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
     pub(super) fn fn_arg_field(
         &self,
         arg: &FnArg<'tcx, M::Provenance>,
-        field: usize,
+        field: FieldIdx,
     ) -> InterpResult<'tcx, FnArg<'tcx, M::Provenance>> {
         interp_ok(match arg {
             FnArg::Copy(op) => FnArg::Copy(self.project_field(op, field)?),
@@ -600,10 +600,9 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
                         Cow::from(
                             args.iter()
                                 .map(|a| interp_ok(a.clone()))
-                                .chain(
-                                    (0..untuple_arg.layout().fields.count())
-                                        .map(|i| self.fn_arg_field(untuple_arg, i)),
-                                )
+                                .chain((0..untuple_arg.layout().fields.count()).map(|i| {
+                                    self.fn_arg_field(untuple_arg, FieldIdx::from_usize(i))
+                                }))
                                 .collect::<InterpResult<'_, Vec<_>>>()?,
                         )
                     } else {

compiler/rustc_const_eval/src/interpret/cast.rs

@@ -1,6 +1,6 @@
 use std::assert_matches::assert_matches;
 
-use rustc_abi::Integer;
+use rustc_abi::{FieldIdx, Integer};
 use rustc_apfloat::ieee::{Double, Half, Quad, Single};
 use rustc_apfloat::{Float, FloatConvert};
 use rustc_middle::mir::CastKind;
@@ -484,6 +484,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
                 let mut found_cast_field = false;
                 for i in 0..src.layout.fields.count() {
                     let cast_ty_field = cast_ty.field(self, i);
+                    let i = FieldIdx::from_usize(i);
                     let src_field = self.project_field(src, i)?;
                     let dst_field = self.project_field(dest, i)?;
                     if src_field.layout.is_1zst() && cast_ty_field.is_1zst() {

compiler/rustc_const_eval/src/interpret/discriminant.rs

@@ -1,6 +1,6 @@
 //! Functions for reading and writing discriminants of multi-variant layouts (enums and coroutines).
 
-use rustc_abi::{self as abi, TagEncoding, VariantIdx, Variants};
+use rustc_abi::{self as abi, FieldIdx, TagEncoding, VariantIdx, Variants};
 use rustc_middle::ty::layout::{LayoutOf, PrimitiveExt, TyAndLayout};
 use rustc_middle::ty::{self, CoroutineArgsExt, ScalarInt, Ty};
 use rustc_middle::{mir, span_bug};
@@ -231,7 +231,7 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
         &self,
         layout: TyAndLayout<'tcx>,
         variant_index: VariantIdx,
-    ) -> InterpResult<'tcx, Option<(ScalarInt, usize)>> {
+    ) -> InterpResult<'tcx, Option<(ScalarInt, FieldIdx)>> {
         // Layout computation excludes uninhabited variants from consideration.
         // Therefore, there's no way to represent those variants in the given layout.
         // Essentially, uninhabited variants do not have a tag that corresponds to their

compiler/rustc_const_eval/src/interpret/operand.rs

@@ -12,6 +12,7 @@ use rustc_middle::ty::layout::{HasTyCtxt, HasTypingEnv, LayoutOf, TyAndLayout};
 use rustc_middle::ty::print::{FmtPrinter, PrettyPrinter};
 use rustc_middle::ty::{ConstInt, ScalarInt, Ty, TyCtxt};
 use rustc_middle::{bug, mir, span_bug, ty};
+use rustc_span::DUMMY_SP;
 use tracing::trace;
 
 use super::{
@@ -307,7 +308,7 @@ impl<'tcx, Prov: Provenance> ImmTy<'tcx, Prov> {
     #[inline]
     pub fn from_ordering(c: std::cmp::Ordering, tcx: TyCtxt<'tcx>) -> Self {
         // Can use any typing env, since `Ordering` is always monomorphic.
-        let ty = tcx.ty_ordering_enum(None);
+        let ty = tcx.ty_ordering_enum(DUMMY_SP);
         let layout =
             tcx.layout_of(ty::TypingEnv::fully_monomorphized().as_query_input(ty)).unwrap();
         Self::from_scalar(Scalar::Int(c.into()), layout)