Auto merge of #65733 - Centril:rollup-0zth66f, r=Centril

Rollup of 12 pull requests

Successful merges:

 - #64178 (More Clippy fixes for alloc, core and std)
 - #65144 (Add Cow::is_borrowed and Cow::is_owned)
 - #65193 (Lockless LintStore)
 - #65479 (Add the `matches!( $expr, $pat ) -> bool` macro)
 - #65518 (Avoid ICE when checking `Destination` of `break` inside a closure)
 - #65583 (rustc_metadata: use a table for super_predicates, fn_sig, impl_trait_ref.)
 - #65641 (Derive `Rustc{En,De}codable` for `TokenStream`.)
 - #65648 (Eliminate `intersect_opt`.)
 - #65657 (Remove `InternedString`)
 - #65691 (Update E0659 error code long explanation to 2018 edition)
 - #65696 (Fix an issue with const inference variables sticking around under Chalk + NLL)
 - #65704 (relax ExactSizeIterator bound on write_bytes)

Failed merges:

r? @ghost

Cargo.lock

@@ -3483,6 +3483,7 @@ dependencies = [
  "rustc_data_structures",
  "rustc_errors",
  "rustc_interface",
+ "rustc_lint",
  "rustc_metadata",
  "rustc_mir",
  "rustc_plugin",

src/liballoc/borrow.rs

@@ -207,6 +207,47 @@ impl<B: ?Sized + ToOwned> Clone for Cow<'_, B> {
 }
 
 impl<B: ?Sized + ToOwned> Cow<'_, B> {
+    /// Returns true if the data is borrowed, i.e. if `to_mut` would require additional work.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(cow_is_borrowed)]
+    /// use std::borrow::Cow;
+    ///
+    /// let cow = Cow::Borrowed("moo");
+    /// assert!(cow.is_borrowed());
+    ///
+    /// let bull: Cow<'_, str> = Cow::Owned("...moo?".to_string());
+    /// assert!(!bull.is_borrowed());
+    /// ```
+    #[unstable(feature = "cow_is_borrowed", issue = "65143")]
+    pub fn is_borrowed(&self) -> bool {
+        match *self {
+            Borrowed(_) => true,
+            Owned(_) => false,
+        }
+    }
+
+    /// Returns true if the data is owned, i.e. if `to_mut` would be a no-op.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(cow_is_borrowed)]
+    /// use std::borrow::Cow;
+    ///
+    /// let cow: Cow<'_, str> = Cow::Owned("moo".to_string());
+    /// assert!(cow.is_owned());
+    ///
+    /// let bull = Cow::Borrowed("...moo?");
+    /// assert!(!bull.is_owned());
+    /// ```
+    #[unstable(feature = "cow_is_borrowed", issue = "65143")]
+    pub fn is_owned(&self) -> bool {
+        !self.is_borrowed()
+    }
+
     /// Acquires a mutable reference to the owned form of the data.
     ///
     /// Clones the data if it is not already owned.

src/liballoc/collections/vec_deque.rs

@@ -1817,7 +1817,7 @@ impl<T> VecDeque<T> {
             }
         }
 
-        return elem;
+        elem
     }
 
     /// Splits the `VecDeque` into two at the given index.

src/liballoc/lib.rs

@@ -85,6 +85,7 @@
 #![feature(const_generic_impls_guard)]
 #![feature(const_generics)]
 #![feature(const_in_array_repeat_expressions)]
+#![feature(cow_is_borrowed)]
 #![feature(dispatch_from_dyn)]
 #![feature(core_intrinsics)]
 #![feature(container_error_extra)]

src/liballoc/str.rs

@@ -456,7 +456,7 @@ impl str {
                 }
             }
         }
-        return s;
+        s
     }
 
     /// Converts a [`Box<str>`] into a [`String`] without copying or allocating.

src/liballoc/sync.rs

@@ -1638,7 +1638,7 @@ impl<T: ?Sized> Clone for Weak<T> {
             }
         }
 
-        return Weak { ptr: self.ptr };
+        Weak { ptr: self.ptr }
     }
 }
 

src/libcore/fmt/mod.rs

@@ -2025,7 +2025,7 @@ impl<T: ?Sized> Pointer for *const T {
         if f.alternate() {
             f.flags |= 1 << (FlagV1::SignAwareZeroPad as u32);
 
-            if let None = f.width {
+            if f.width.is_none() {
                 f.width = Some(((mem::size_of::<usize>() * 8) / 4) + 2);
             }
         }

src/libcore/macros.rs

@@ -238,6 +238,33 @@ macro_rules! debug_assert_ne {
     ($($arg:tt)*) => (if $crate::cfg!(debug_assertions) { $crate::assert_ne!($($arg)*); })
 }
 
+/// Returns whether the given expression matches any of the given patterns.
+///
+/// Like in a `match` expression, the pattern can be optionally followed by `if`
+/// and a guard expression that has access to names bound by the pattern.
+///
+/// # Examples
+///
+/// ```
+/// #![feature(matches_macro)]
+///
+/// let foo = 'f';
+/// assert!(matches!(foo, 'A'..='Z' | 'a'..='z'));
+///
+/// let bar = Some(4);
+/// assert!(matches!(bar, Some(x) if x > 2));
+/// ```
+#[macro_export]
+#[unstable(feature = "matches_macro", issue = "65721")]
+macro_rules! matches {
+    ($expression:expr, $( $pattern:pat )|+ $( if $guard: expr )?) => {
+        match $expression {
+            $( $pattern )|+ $( if $guard )? => true,
+            _ => false
+        }
+    }
+}
+
 /// Unwraps a result or propagates its error.
 ///
 /// The `?` operator was added to replace `try!` and should be used instead.

src/libcore/num/dec2flt/algorithm.rs

@@ -143,13 +143,12 @@ pub fn fast_path<T: RawFloat>(integral: &[u8], fractional: &[u8], e: i64) -> Opt
 /// > not a bound for the true error, but bounds the difference between the approximation z and
 /// > the best possible approximation that uses p bits of significand.)
 pub fn bellerophon<T: RawFloat>(f: &Big, e: i16) -> T {
-    let slop;
-    if f <= &Big::from_u64(T::MAX_SIG) {
+    let slop = if f <= &Big::from_u64(T::MAX_SIG) {
         // The cases abs(e) < log5(2^N) are in fast_path()
-        slop = if e >= 0 { 0 } else { 3 };
+        if e >= 0 { 0 } else { 3 }
     } else {
-        slop = if e >= 0 { 1 } else { 4 };
-    }
+        if e >= 0 { 1 } else { 4 }
+    };
     let z = rawfp::big_to_fp(f).mul(&power_of_ten(e)).normalize();
     let exp_p_n = 1 << (P - T::SIG_BITS as u32);
     let lowbits: i64 = (z.f % exp_p_n) as i64;

src/libcore/option.rs

@@ -837,9 +837,8 @@ impl<T> Option<T> {
     #[inline]
     #[stable(feature = "option_entry", since = "1.20.0")]
     pub fn get_or_insert_with<F: FnOnce() -> T>(&mut self, f: F) -> &mut T {
-        match *self {
-            None => *self = Some(f()),
-            _ => (),
+        if let None = *self {
+            *self = Some(f());
         }
 
         match *self {

src/libpanic_unwind/gcc.rs

@@ -156,21 +156,21 @@ unsafe extern "C" fn rust_eh_personality(version: c_int,
     if actions as i32 & uw::_UA_SEARCH_PHASE as i32 != 0 {
         match eh_action {
             EHAction::None |
-            EHAction::Cleanup(_) => return uw::_URC_CONTINUE_UNWIND,
-            EHAction::Catch(_) => return uw::_URC_HANDLER_FOUND,
-            EHAction::Terminate => return uw::_URC_FATAL_PHASE1_ERROR,
+            EHAction::Cleanup(_) => uw::_URC_CONTINUE_UNWIND,
+            EHAction::Catch(_) => uw::_URC_HANDLER_FOUND,
+            EHAction::Terminate => uw::_URC_FATAL_PHASE1_ERROR,
         }
     } else {
         match eh_action {
-            EHAction::None => return uw::_URC_CONTINUE_UNWIND,
+            EHAction::None => uw::_URC_CONTINUE_UNWIND,
             EHAction::Cleanup(lpad) |
             EHAction::Catch(lpad) => {
                 uw::_Unwind_SetGR(context, UNWIND_DATA_REG.0, exception_object as uintptr_t);
                 uw::_Unwind_SetGR(context, UNWIND_DATA_REG.1, 0);
                 uw::_Unwind_SetIP(context, lpad);
-                return uw::_URC_INSTALL_CONTEXT;
+                uw::_URC_INSTALL_CONTEXT
             }
-            EHAction::Terminate => return uw::_URC_FATAL_PHASE2_ERROR,
+            EHAction::Terminate => uw::_URC_FATAL_PHASE2_ERROR,
         }
     }
 }

src/libpanic_unwind/seh64_gnu.rs

@@ -46,7 +46,7 @@ pub fn payload() -> *mut u8 {
 
 pub unsafe fn cleanup(ptr: *mut u8) -> Box<dyn Any + Send> {
     let panic_ctx = Box::from_raw(ptr as *mut PanicData);
-    return panic_ctx.data;
+    panic_ctx.data
 }
 
 // SEH doesn't support resuming unwinds after calling a landing pad like

src/librustc/dep_graph/dep_node.rs

@@ -59,7 +59,7 @@ use crate::ich::{Fingerprint, StableHashingContext};
 use rustc_data_structures::stable_hasher::{StableHasher, HashStable};
 use std::fmt;
 use std::hash::Hash;
-use syntax_pos::symbol::InternedString;
+use syntax_pos::symbol::Symbol;
 use crate::traits;
 use crate::traits::query::{
     CanonicalProjectionGoal, CanonicalTyGoal, CanonicalTypeOpAscribeUserTypeGoal,
@@ -426,7 +426,7 @@ rustc_dep_node_append!([define_dep_nodes!][ <'tcx>
 
     [anon] TraitSelect,
 
-    [] CompileCodegenUnit(InternedString),
+    [] CompileCodegenUnit(Symbol),
 
     [eval_always] Analysis(CrateNum),
 ]);

src/librustc/hir/lowering.rs

@@ -792,15 +792,15 @@ impl<'a> LoweringContext<'a> {
         // really show up for end-user.
         let (str_name, kind) = match hir_name {
             ParamName::Plain(ident) => (
-                ident.as_interned_str(),
+                ident.name,
                 hir::LifetimeParamKind::InBand,
             ),
             ParamName::Fresh(_) => (
-                kw::UnderscoreLifetime.as_interned_str(),
+                kw::UnderscoreLifetime,
                 hir::LifetimeParamKind::Elided,
             ),
             ParamName::Error => (
-                kw::UnderscoreLifetime.as_interned_str(),
+                kw::UnderscoreLifetime,
                 hir::LifetimeParamKind::Error,
             ),
         };
@@ -1590,7 +1590,7 @@ impl<'a> LoweringContext<'a> {
                     self.context.resolver.definitions().create_def_with_parent(
                         self.parent,
                         def_node_id,
-                        DefPathData::LifetimeNs(name.ident().as_interned_str()),
+                        DefPathData::LifetimeNs(name.ident().name),
                         ExpnId::root(),
                         lifetime.span);
 

src/librustc/hir/map/collector.rs

@@ -186,13 +186,13 @@ impl<'a, 'hir> NodeCollector<'a, 'hir> {
             });
 
         let mut upstream_crates: Vec<_> = cstore.crates_untracked().iter().map(|&cnum| {
-            let name = cstore.crate_name_untracked(cnum).as_interned_str();
+            let name = cstore.crate_name_untracked(cnum);
             let disambiguator = cstore.crate_disambiguator_untracked(cnum).to_fingerprint();
             let hash = cstore.crate_hash_untracked(cnum);
             (name, disambiguator, hash)
         }).collect();
 
-        upstream_crates.sort_unstable_by_key(|&(name, dis, _)| (name, dis));
+        upstream_crates.sort_unstable_by_key(|&(name, dis, _)| (name.as_str(), dis));
 
         // We hash the final, remapped names of all local source files so we
         // don't have to include the path prefix remapping commandline args.

src/librustc/hir/map/def_collector.rs

@@ -57,7 +57,7 @@ impl<'a> DefCollector<'a> {
 
         // For async functions, we need to create their inner defs inside of a
         // closure to match their desugared representation.
-        let fn_def_data = DefPathData::ValueNs(name.as_interned_str());
+        let fn_def_data = DefPathData::ValueNs(name);
         let fn_def = self.create_def(id, fn_def_data, span);
         return self.with_parent(fn_def, |this| {
             this.create_def(return_impl_trait_id, DefPathData::ImplTrait, span);
@@ -83,8 +83,7 @@ impl<'a> DefCollector<'a> {
                 .unwrap_or_else(|| {
                     let node_id = NodeId::placeholder_from_expn_id(self.expansion);
                     sym::integer(self.definitions.placeholder_field_indices[&node_id])
-                })
-                .as_interned_str();
+                });
             let def = self.create_def(field.id, DefPathData::ValueNs(name), field.span);
             self.with_parent(def, |this| visit::walk_struct_field(this, field));
         }
@@ -109,7 +108,7 @@ impl<'a> visit::Visitor<'a> for DefCollector<'a> {
             ItemKind::Mod(..) | ItemKind::Trait(..) | ItemKind::TraitAlias(..) |
             ItemKind::Enum(..) | ItemKind::Struct(..) | ItemKind::Union(..) |
             ItemKind::OpaqueTy(..) | ItemKind::ExternCrate(..) | ItemKind::ForeignMod(..) |
-            ItemKind::TyAlias(..) => DefPathData::TypeNs(i.ident.as_interned_str()),
+            ItemKind::TyAlias(..) => DefPathData::TypeNs(i.ident.name),
             ItemKind::Fn(
                 ref decl,
                 ref header,
@@ -127,8 +126,8 @@ impl<'a> visit::Visitor<'a> for DefCollector<'a> {
                 )
             }
             ItemKind::Static(..) | ItemKind::Const(..) | ItemKind::Fn(..) =>
-                DefPathData::ValueNs(i.ident.as_interned_str()),
-            ItemKind::MacroDef(..) => DefPathData::MacroNs(i.ident.as_interned_str()),
+                DefPathData::ValueNs(i.ident.name),
+            ItemKind::MacroDef(..) => DefPathData::MacroNs(i.ident.name),
             ItemKind::Mac(..) => return self.visit_macro_invoc(i.id),
             ItemKind::GlobalAsm(..) => DefPathData::Misc,
             ItemKind::Use(..) => {
@@ -162,7 +161,7 @@ impl<'a> visit::Visitor<'a> for DefCollector<'a> {
         }
 
         let def = self.create_def(foreign_item.id,
-                                  DefPathData::ValueNs(foreign_item.ident.as_interned_str()),
+                                  DefPathData::ValueNs(foreign_item.ident.name),
                                   foreign_item.span);
 
         self.with_parent(def, |this| {
@@ -175,7 +174,7 @@ impl<'a> visit::Visitor<'a> for DefCollector<'a> {
             return self.visit_macro_invoc(v.id);
         }
         let def = self.create_def(v.id,
-                                  DefPathData::TypeNs(v.ident.as_interned_str()),
+                                  DefPathData::TypeNs(v.ident.name),
                                   v.span);
         self.with_parent(def, |this| {
             if let Some(ctor_hir_id) = v.data.ctor_id() {
@@ -202,7 +201,7 @@ impl<'a> visit::Visitor<'a> for DefCollector<'a> {
             self.visit_macro_invoc(param.id);
             return;
         }
-        let name = param.ident.as_interned_str();
+        let name = param.ident.name;
         let def_path_data = match param.kind {
             GenericParamKind::Lifetime { .. } => DefPathData::LifetimeNs(name),
             GenericParamKind::Type { .. } => DefPathData::TypeNs(name),
@@ -216,9 +215,9 @@ impl<'a> visit::Visitor<'a> for DefCollector<'a> {
     fn visit_trait_item(&mut self, ti: &'a TraitItem) {
         let def_data = match ti.kind {
             TraitItemKind::Method(..) | TraitItemKind::Const(..) =>
-                DefPathData::ValueNs(ti.ident.as_interned_str()),
+                DefPathData::ValueNs(ti.ident.name),
             TraitItemKind::Type(..) => {
-                DefPathData::TypeNs(ti.ident.as_interned_str())
+                DefPathData::TypeNs(ti.ident.name)
             },
             TraitItemKind::Macro(..) => return self.visit_macro_invoc(ti.id),
         };
@@ -243,12 +242,10 @@ impl<'a> visit::Visitor<'a> for DefCollector<'a> {
                     body,
                 )
             }
-            ImplItemKind::Method(..) | ImplItemKind::Const(..) =>
-                DefPathData::ValueNs(ii.ident.as_interned_str()),
+            ImplItemKind::Method(..) |
+            ImplItemKind::Const(..) => DefPathData::ValueNs(ii.ident.name),
             ImplItemKind::TyAlias(..) |
-            ImplItemKind::OpaqueTy(..) => {
-                DefPathData::TypeNs(ii.ident.as_interned_str())
-            },
+            ImplItemKind::OpaqueTy(..) => DefPathData::TypeNs(ii.ident.name),
             ImplItemKind::Macro(..) => return self.visit_macro_invoc(ii.id),
         };
 

src/librustc/hir/map/definitions.rs

@@ -18,7 +18,7 @@ use std::fmt::Write;
 use std::hash::Hash;
 use syntax::ast;
 use syntax_expand::hygiene::ExpnId;
-use syntax::symbol::{Symbol, sym, InternedString};
+use syntax::symbol::{Symbol, sym};
 use syntax_pos::{Span, DUMMY_SP};
 
 /// The `DefPathTable` maps `DefIndex`es to `DefKey`s and vice versa.
@@ -136,7 +136,9 @@ impl DefKey {
 
         ::std::mem::discriminant(data).hash(&mut hasher);
         if let Some(name) = data.get_opt_name() {
-            name.hash(&mut hasher);
+            // Get a stable hash by considering the symbol chars rather than
+            // the symbol index.
+            name.as_str().hash(&mut hasher);
         }
 
         disambiguator.hash(&mut hasher);
@@ -218,7 +220,7 @@ impl DefPath {
         for component in &self.data {
             write!(s,
                    "::{}[{}]",
-                   component.data.as_interned_str(),
+                   component.data.as_symbol(),
                    component.disambiguator)
                 .unwrap();
         }
@@ -238,11 +240,11 @@ impl DefPath {
 
         for component in &self.data {
             if component.disambiguator == 0 {
-                write!(s, "::{}", component.data.as_interned_str()).unwrap();
+                write!(s, "::{}", component.data.as_symbol()).unwrap();
             } else {
                 write!(s,
                        "{}[{}]",
-                       component.data.as_interned_str(),
+                       component.data.as_symbol(),
                        component.disambiguator)
                        .unwrap();
             }
@@ -262,11 +264,11 @@ impl DefPath {
             opt_delimiter.map(|d| s.push(d));
             opt_delimiter = Some('-');
             if component.disambiguator == 0 {
-                write!(s, "{}", component.data.as_interned_str()).unwrap();
+                write!(s, "{}", component.data.as_symbol()).unwrap();
             } else {
                 write!(s,
                        "{}[{}]",
-                       component.data.as_interned_str(),
+                       component.data.as_symbol(),
                        component.disambiguator)
                        .unwrap();
             }
@@ -290,13 +292,13 @@ pub enum DefPathData {
     /// An impl.
     Impl,
     /// Something in the type namespace.
-    TypeNs(InternedString),
+    TypeNs(Symbol),
     /// Something in the value namespace.
-    ValueNs(InternedString),
+    ValueNs(Symbol),
     /// Something in the macro namespace.
-    MacroNs(InternedString),
+    MacroNs(Symbol),
     /// Something in the lifetime namespace.
-    LifetimeNs(InternedString),
+    LifetimeNs(Symbol),
     /// A closure expression.
     ClosureExpr,
 
@@ -311,7 +313,7 @@ pub enum DefPathData {
     /// Identifies a piece of crate metadata that is global to a whole crate
     /// (as opposed to just one item). `GlobalMetaData` components are only
     /// supposed to show up right below the crate root.
-    GlobalMetaData(InternedString),
+    GlobalMetaData(Symbol),
 }
 
 #[derive(Copy, Clone, Hash, PartialEq, Eq, PartialOrd, Ord, Debug,
@@ -545,7 +547,7 @@ impl Definitions {
 }
 
 impl DefPathData {
-    pub fn get_opt_name(&self) -> Option<InternedString> {
+    pub fn get_opt_name(&self) -> Option<Symbol> {
         use self::DefPathData::*;
         match *self {
             TypeNs(name) |
@@ -564,15 +566,15 @@ impl DefPathData {
         }
     }
 
-    pub fn as_interned_str(&self) -> InternedString {
+    pub fn as_symbol(&self) -> Symbol {
         use self::DefPathData::*;
-        let s = match *self {
+        match *self {
             TypeNs(name) |
             ValueNs(name) |
             MacroNs(name) |
             LifetimeNs(name) |
             GlobalMetaData(name) => {
-                return name
+                name
             }
             // Note that this does not show up in user print-outs.
             CrateRoot => sym::double_braced_crate,
@@ -582,13 +584,11 @@ impl DefPathData {
             Ctor => sym::double_braced_constructor,
             AnonConst => sym::double_braced_constant,
             ImplTrait => sym::double_braced_opaque,
-        };
-
-        s.as_interned_str()
+        }
     }
 
     pub fn to_string(&self) -> String {
-        self.as_interned_str().to_string()
+        self.as_symbol().to_string()
     }
 }
 
@@ -610,7 +610,7 @@ macro_rules! define_global_metadata_kind {
                     definitions.create_def_with_parent(
                         CRATE_DEF_INDEX,
                         ast::DUMMY_NODE_ID,
-                        DefPathData::GlobalMetaData(instance.name().as_interned_str()),
+                        DefPathData::GlobalMetaData(instance.name()),
                         ExpnId::root(),
                         DUMMY_SP
                     );
@@ -624,7 +624,7 @@ macro_rules! define_global_metadata_kind {
                 let def_key = DefKey {
                     parent: Some(CRATE_DEF_INDEX),
                     disambiguated_data: DisambiguatedDefPathData {
-                        data: DefPathData::GlobalMetaData(self.name().as_interned_str()),
+                        data: DefPathData::GlobalMetaData(self.name()),
                         disambiguator: 0,
                     }
                 };

src/librustc/hir/mod.rs

@@ -19,7 +19,7 @@ use crate::ty::query::Providers;
 use crate::util::nodemap::{NodeMap, FxHashSet};
 
 use errors::FatalError;
-use syntax_pos::{Span, DUMMY_SP, symbol::InternedString, MultiSpan};
+use syntax_pos::{Span, DUMMY_SP, MultiSpan};
 use syntax::source_map::Spanned;
 use syntax::ast::{self, CrateSugar, Ident, Name, NodeId, AsmDialect};
 use syntax::ast::{Attribute, Label, LitKind, StrStyle, FloatTy, IntTy, UintTy};
@@ -628,9 +628,9 @@ impl Generics {
         own_counts
     }
 
-    pub fn get_named(&self, name: InternedString) -> Option<&GenericParam> {
+    pub fn get_named(&self, name: Symbol) -> Option<&GenericParam> {
         for param in &self.params {
-            if name == param.name.ident().as_interned_str() {
+            if name == param.name.ident().name {
                 return Some(param);
             }
         }

src/librustc/ich/impls_syntax.rs

@@ -9,7 +9,7 @@ use std::mem;
 use syntax::ast;
 use syntax::feature_gate;
 use syntax::parse::token;
-use syntax::symbol::InternedString;
+use syntax::symbol::LocalInternedString;
 use syntax::tokenstream;
 use syntax_pos::SourceFile;
 
@@ -18,20 +18,21 @@ use crate::hir::def_id::{DefId, CrateNum, CRATE_DEF_INDEX};
 use smallvec::SmallVec;
 use rustc_data_structures::stable_hasher::{HashStable, ToStableHashKey, StableHasher};
 
-impl<'a> HashStable<StableHashingContext<'a>> for InternedString {
+impl<'a> HashStable<StableHashingContext<'a>> for LocalInternedString {
     #[inline]
     fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
-        self.with(|s| s.hash_stable(hcx, hasher))
+        let str = self as &str;
+        str.hash_stable(hcx, hasher)
     }
 }
 
-impl<'a> ToStableHashKey<StableHashingContext<'a>> for InternedString {
-    type KeyType = InternedString;
+impl<'a> ToStableHashKey<StableHashingContext<'a>> for LocalInternedString {
+    type KeyType = LocalInternedString;
 
     #[inline]
     fn to_stable_hash_key(&self,
                           _: &StableHashingContext<'a>)
-                          -> InternedString {
+                          -> LocalInternedString {
         self.clone()
     }
 }
@@ -44,13 +45,13 @@ impl<'a> HashStable<StableHashingContext<'a>> for ast::Name {
 }
 
 impl<'a> ToStableHashKey<StableHashingContext<'a>> for ast::Name {
-    type KeyType = InternedString;
+    type KeyType = LocalInternedString;
 
     #[inline]
     fn to_stable_hash_key(&self,
                           _: &StableHashingContext<'a>)
-                          -> InternedString {
-        self.as_interned_str()
+                          -> LocalInternedString {
+        self.as_str()
     }
 }
 

src/librustc/infer/combine.rs

@@ -494,7 +494,7 @@ impl TypeRelation<'tcx> for Generalizer<'_, 'tcx> {
                 if sub_vid == self.for_vid_sub_root {
                     // If sub-roots are equal, then `for_vid` and
                     // `vid` are related via subtyping.
-                    return Err(TypeError::CyclicTy(self.root_ty));
+                    Err(TypeError::CyclicTy(self.root_ty))
                 } else {
                     match variables.probe(vid) {
                         TypeVariableValue::Known { value: u } => {
@@ -527,7 +527,7 @@ impl TypeRelation<'tcx> for Generalizer<'_, 'tcx> {
                             let u = self.tcx().mk_ty_var(new_var_id);
                             debug!("generalize: replacing original vid={:?} with new={:?}",
                                    vid, u);
-                            return Ok(u);
+                            Ok(u)
                         }
                     }
                 }
@@ -602,19 +602,26 @@ impl TypeRelation<'tcx> for Generalizer<'_, 'tcx> {
     ) -> RelateResult<'tcx, &'tcx ty::Const<'tcx>> {
         assert_eq!(c, c2); // we are abusing TypeRelation here; both LHS and RHS ought to be ==
 
-        match c {
-            ty::Const { val: ConstValue::Infer(InferConst::Var(vid)), .. } => {
+        match c.val {
+            ConstValue::Infer(InferConst::Var(vid)) => {
                 let mut variable_table = self.infcx.const_unification_table.borrow_mut();
-                match variable_table.probe_value(*vid).val.known() {
-                    Some(u) => {
-                        self.relate(&u, &u)
+                let var_value = variable_table.probe_value(vid);
+                match var_value.val {
+                    ConstVariableValue::Known { value: u } => self.relate(&u, &u),
+                    ConstVariableValue::Unknown { universe } => {
+                        if self.for_universe.can_name(universe) {
+                            Ok(c)
+                        } else {
+                            let new_var_id = variable_table.new_key(ConstVarValue {
+                                origin: var_value.origin,
+                                val: ConstVariableValue::Unknown { universe: self.for_universe },
+                            });
+                            Ok(self.tcx().mk_const_var(new_var_id, c.ty))
+                        }
                     }
-                    None => Ok(c),
                 }
             }
-            _ => {
-                relate::super_relate_consts(self, c, c)
-            }
+            _ => relate::super_relate_consts(self, c, c),
         }
     }
 }

src/librustc/infer/error_reporting/mod.rs

@@ -542,7 +542,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
                 disambiguated_data: &DisambiguatedDefPathData,
             ) -> Result<Self::Path, Self::Error> {
                 let mut path = print_prefix(self)?;
-                path.push(disambiguated_data.data.as_interned_str().to_string());
+                path.push(disambiguated_data.data.as_symbol().to_string());
                 Ok(path)
             }
             fn path_generic_args(

src/librustc/infer/mod.rs

@@ -32,7 +32,7 @@ use std::cell::{Cell, Ref, RefCell, RefMut};
 use std::collections::BTreeMap;
 use std::fmt;
 use syntax::ast;
-use syntax_pos::symbol::InternedString;
+use syntax_pos::symbol::Symbol;
 use syntax_pos::Span;
 
 use self::combine::CombineFields;
@@ -392,7 +392,7 @@ pub enum RegionVariableOrigin {
     Coercion(Span),
 
     /// Region variables created as the values for early-bound regions
-    EarlyBoundRegion(Span, InternedString),
+    EarlyBoundRegion(Span, Symbol),
 
     /// Region variables created for bound regions
     /// in a function or method that is called

src/librustc/infer/nll_relate/mod.rs

@@ -27,7 +27,8 @@ use crate::ty::error::TypeError;
 use crate::ty::fold::{TypeFoldable, TypeVisitor};
 use crate::ty::relate::{self, Relate, RelateResult, TypeRelation};
 use crate::ty::subst::GenericArg;
-use crate::ty::{self, Ty, TyCtxt};
+use crate::ty::{self, Ty, TyCtxt, InferConst};
+use crate::infer::{ConstVariableValue, ConstVarValue};
 use crate::mir::interpret::ConstValue;
 use rustc_data_structures::fx::FxHashMap;
 use std::fmt::Debug;
@@ -324,7 +325,7 @@ where
         let vid = pair.vid();
         let value_ty = pair.value_ty();
 
-        // FIXME -- this logic assumes invariance, but that is wrong.
+        // FIXME(invariance) -- this logic assumes invariance, but that is wrong.
         // This only presently applies to chalk integration, as NLL
         // doesn't permit type variables to appear on both sides (and
         // doesn't use lazy norm).
@@ -616,15 +617,21 @@ where
     fn consts(
         &mut self,
         a: &'tcx ty::Const<'tcx>,
-        b: &'tcx ty::Const<'tcx>,
+        mut b: &'tcx ty::Const<'tcx>,
     ) -> RelateResult<'tcx, &'tcx ty::Const<'tcx>> {
-        if let ty::Const { val: ConstValue::Bound(..), .. } = a {
-            // FIXME(const_generics): I'm unsure how this branch should actually be handled,
-            // so this is probably not correct.
-            self.infcx.super_combine_consts(self, a, b)
-        } else {
-            debug!("consts(a={:?}, b={:?}, variance={:?})", a, b, self.ambient_variance);
-            relate::super_relate_consts(self, a, b)
+        let a = self.infcx.shallow_resolve(a);
+
+        if !D::forbid_inference_vars() {
+            b = self.infcx.shallow_resolve(b);
+        }
+
+        match b.val {
+            ConstValue::Infer(InferConst::Var(_)) if D::forbid_inference_vars() => {
+                // Forbid inference variables in the RHS.
+                bug!("unexpected inference var {:?}", b)
+            }
+            // FIXME(invariance): see the related FIXME above.
+            _ => self.infcx.super_combine_consts(self, a, b)
         }
     }
 
@@ -991,15 +998,28 @@ where
         a: &'tcx ty::Const<'tcx>,
         _: &'tcx ty::Const<'tcx>,
     ) -> RelateResult<'tcx, &'tcx ty::Const<'tcx>> {
-        debug!("TypeGeneralizer::consts(a={:?})", a);
-
-        if let ty::Const { val: ConstValue::Bound(..), .. } = a {
-            bug!(
-                "unexpected inference variable encountered in NLL generalization: {:?}",
-                a
-            );
-        } else {
-            relate::super_relate_consts(self, a, a)
+        match a.val {
+            ConstValue::Infer(InferConst::Var(_)) if D::forbid_inference_vars() => {
+                bug!(
+                    "unexpected inference variable encountered in NLL generalization: {:?}",
+                    a
+                );
+            }
+            ConstValue::Infer(InferConst::Var(vid)) => {
+                let mut variable_table = self.infcx.const_unification_table.borrow_mut();
+                let var_value = variable_table.probe_value(vid);
+                match var_value.val.known() {
+                    Some(u) => self.relate(&u, &u),
+                    None => {
+                        let new_var_id = variable_table.new_key(ConstVarValue {
+                            origin: var_value.origin,
+                            val: ConstVariableValue::Unknown { universe: self.universe },
+                        });
+                        Ok(self.tcx().mk_const_var(new_var_id, a.ty))
+                    }
+                }
+            }
+            _ => relate::super_relate_consts(self, a, a),
         }
     }
 

src/librustc/infer/type_variable.rs

@@ -1,4 +1,4 @@
-use syntax::symbol::InternedString;
+use syntax::symbol::Symbol;
 use syntax_pos::Span;
 use crate::ty::{self, Ty, TyVid};
 
@@ -49,7 +49,7 @@ pub enum TypeVariableOriginKind {
     MiscVariable,
     NormalizeProjectionType,
     TypeInference,
-    TypeParameterDefinition(InternedString),
+    TypeParameterDefinition(Symbol),
 
     /// One of the upvars or closure kind parameters in a `ClosureSubsts`
     /// (before it has been determined).

src/librustc/infer/unify_key.rs

@@ -3,7 +3,7 @@ use crate::mir::interpret::ConstValue;
 use rustc_data_structures::unify::{NoError, EqUnifyValue, UnifyKey, UnifyValue, UnificationTable};
 use rustc_data_structures::unify::InPlace;
 use syntax_pos::{Span, DUMMY_SP};
-use syntax::symbol::InternedString;
+use syntax::symbol::Symbol;
 
 use std::cmp;
 use std::marker::PhantomData;
@@ -90,7 +90,7 @@ pub struct ConstVariableOrigin {
 pub enum ConstVariableOriginKind {
     MiscVariable,
     ConstInference,
-    ConstParameterDefinition(InternedString),
+    ConstParameterDefinition(Symbol),
     SubstitutionPlaceholder,
 }
 

src/librustc/lint/builtin.rs

@@ -4,11 +4,12 @@
 //! compiler code, rather than using their own custom pass. Those
 //! lints are all available in `rustc_lint::builtin`.
 
-use crate::lint::{LintPass, LateLintPass, LintArray};
+use crate::lint::{LintPass, LateLintPass, LintArray, FutureIncompatibleInfo};
 use crate::middle::stability;
 use crate::session::Session;
 use errors::{Applicability, DiagnosticBuilder, pluralise};
 use syntax::ast;
+use syntax::edition::Edition;
 use syntax::source_map::Span;
 use syntax::symbol::Symbol;
 
@@ -22,7 +23,7 @@ declare_lint! {
     pub CONST_ERR,
     Deny,
     "constant evaluation detected erroneous expression",
-    report_in_external_macro: true
+    report_in_external_macro
 }
 
 declare_lint! {
@@ -71,7 +72,7 @@ declare_lint! {
     pub UNREACHABLE_CODE,
     Warn,
     "detects unreachable code paths",
-    report_in_external_macro: true
+    report_in_external_macro
 }
 
 declare_lint! {
@@ -131,7 +132,11 @@ declare_lint! {
 declare_lint! {
     pub PRIVATE_IN_PUBLIC,
     Warn,
-    "detect private items in public interfaces not caught by the old implementation"
+    "detect private items in public interfaces not caught by the old implementation",
+    @future_incompatible = FutureIncompatibleInfo {
+        reference: "issue #34537 <https://github.com/rust-lang/rust/issues/34537>",
+        edition: None,
+    };
 }
 
 declare_lint! {
@@ -143,13 +148,21 @@ declare_lint! {
 declare_lint! {
     pub PUB_USE_OF_PRIVATE_EXTERN_CRATE,
     Deny,
-    "detect public re-exports of private extern crates"
+    "detect public re-exports of private extern crates",
+    @future_incompatible = FutureIncompatibleInfo {
+        reference: "issue #34537 <https://github.com/rust-lang/rust/issues/34537>",
+        edition: None,
+    };
 }
 
 declare_lint! {
     pub INVALID_TYPE_PARAM_DEFAULT,
     Deny,
-    "type parameter default erroneously allowed in invalid location"
+    "type parameter default erroneously allowed in invalid location",
+    @future_incompatible = FutureIncompatibleInfo {
+        reference: "issue #36887 <https://github.com/rust-lang/rust/issues/36887>",
+        edition: None,
+    };
 }
 
 declare_lint! {
@@ -161,63 +174,99 @@ declare_lint! {
 declare_lint! {
     pub SAFE_EXTERN_STATICS,
     Deny,
-    "safe access to extern statics was erroneously allowed"
+    "safe access to extern statics was erroneously allowed",
+    @future_incompatible = FutureIncompatibleInfo {
+        reference: "issue #36247 <https://github.com/rust-lang/rust/issues/36247>",
+        edition: None,
+    };
 }
 
 declare_lint! {
     pub SAFE_PACKED_BORROWS,
     Warn,
-    "safe borrows of fields of packed structs were was erroneously allowed"
+    "safe borrows of fields of packed structs were was erroneously allowed",
+    @future_incompatible = FutureIncompatibleInfo {
+        reference: "issue #46043 <https://github.com/rust-lang/rust/issues/46043>",
+        edition: None,
+    };
 }
 
 declare_lint! {
     pub PATTERNS_IN_FNS_WITHOUT_BODY,
     Warn,
-    "patterns in functions without body were erroneously allowed"
+    "patterns in functions without body were erroneously allowed",
+    @future_incompatible = FutureIncompatibleInfo {
+        reference: "issue #35203 <https://github.com/rust-lang/rust/issues/35203>",
+        edition: None,
+    };
 }
 
 declare_lint! {
     pub LEGACY_DIRECTORY_OWNERSHIP,
     Deny,
     "non-inline, non-`#[path]` modules (e.g., `mod foo;`) were erroneously allowed in some files \
-     not named `mod.rs`"
+     not named `mod.rs`",
+     @future_incompatible = FutureIncompatibleInfo {
+         reference: "issue #37872 <https://github.com/rust-lang/rust/issues/37872>",
+         edition: None,
+     };
 }
 
 declare_lint! {
     pub LEGACY_CONSTRUCTOR_VISIBILITY,
     Deny,
-    "detects use of struct constructors that would be invisible with new visibility rules"
+    "detects use of struct constructors that would be invisible with new visibility rules",
+    @future_incompatible = FutureIncompatibleInfo {
+        reference: "issue #39207 <https://github.com/rust-lang/rust/issues/39207>",
+        edition: None,
+    };
 }
 
 declare_lint! {
     pub MISSING_FRAGMENT_SPECIFIER,
     Deny,
-    "detects missing fragment specifiers in unused `macro_rules!` patterns"
+    "detects missing fragment specifiers in unused `macro_rules!` patterns",
+    @future_incompatible = FutureIncompatibleInfo {
+        reference: "issue #40107 <https://github.com/rust-lang/rust/issues/40107>",
+        edition: None,
+    };
 }
 
 declare_lint! {
     pub PARENTHESIZED_PARAMS_IN_TYPES_AND_MODULES,
     Deny,
-    "detects parenthesized generic parameters in type and module names"
+    "detects parenthesized generic parameters in type and module names",
+    @future_incompatible = FutureIncompatibleInfo {
+        reference: "issue #42238 <https://github.com/rust-lang/rust/issues/42238>",
+        edition: None,
+    };
 }
 
 declare_lint! {
     pub LATE_BOUND_LIFETIME_ARGUMENTS,
     Warn,
-    "detects generic lifetime arguments in path segments with late bound lifetime parameters"
+    "detects generic lifetime arguments in path segments with late bound lifetime parameters",
+    @future_incompatible = FutureIncompatibleInfo {
+        reference: "issue #42868 <https://github.com/rust-lang/rust/issues/42868>",
+        edition: None,
+    };
 }
 
 declare_lint! {
     pub ORDER_DEPENDENT_TRAIT_OBJECTS,
     Deny,
-    "trait-object types were treated as different depending on marker-trait order"
+    "trait-object types were treated as different depending on marker-trait order",
+    @future_incompatible = FutureIncompatibleInfo {
+        reference: "issue #56484 <https://github.com/rust-lang/rust/issues/56484>",
+        edition: None,
+    };
 }
 
 declare_lint! {
     pub DEPRECATED,
     Warn,
     "detects use of deprecated items",
-    report_in_external_macro: true
+    report_in_external_macro
 }
 
 declare_lint! {
@@ -253,7 +302,11 @@ declare_lint! {
 declare_lint! {
     pub TYVAR_BEHIND_RAW_POINTER,
     Warn,
-    "raw pointer to an inference variable"
+    "raw pointer to an inference variable",
+    @future_incompatible = FutureIncompatibleInfo {
+        reference: "issue #46906 <https://github.com/rust-lang/rust/issues/46906>",
+        edition: Some(Edition::Edition2018),
+    };
 }
 
 declare_lint! {
@@ -272,19 +325,33 @@ declare_lint! {
     pub ABSOLUTE_PATHS_NOT_STARTING_WITH_CRATE,
     Allow,
     "fully qualified paths that start with a module name \
-     instead of `crate`, `self`, or an extern crate name"
+     instead of `crate`, `self`, or an extern crate name",
+     @future_incompatible = FutureIncompatibleInfo {
+        reference: "issue #53130 <https://github.com/rust-lang/rust/issues/53130>",
+        edition: Some(Edition::Edition2018),
+     };
 }
 
 declare_lint! {
     pub ILLEGAL_FLOATING_POINT_LITERAL_PATTERN,
     Warn,
-    "floating-point literals cannot be used in patterns"
+    "floating-point literals cannot be used in patterns",
+    @future_incompatible = FutureIncompatibleInfo {
+        reference: "issue #41620 <https://github.com/rust-lang/rust/issues/41620>",
+        edition: None,
+    };
 }
 
 declare_lint! {
     pub UNSTABLE_NAME_COLLISIONS,
     Warn,
-    "detects name collision with an existing but unstable method"
+    "detects name collision with an existing but unstable method",
+    @future_incompatible = FutureIncompatibleInfo {
+        reference: "issue #48919 <https://github.com/rust-lang/rust/issues/48919>",
+        edition: None,
+        // Note: this item represents future incompatibility of all unstable functions in the
+        //       standard library, and thus should never be removed or changed to an error.
+    };
 }
 
 declare_lint! {
@@ -302,7 +369,11 @@ declare_lint! {
 declare_lint! {
     pub DUPLICATE_MACRO_EXPORTS,
     Deny,
-    "detects duplicate macro exports"
+    "detects duplicate macro exports",
+    @future_incompatible = FutureIncompatibleInfo {
+        reference: "issue #35896 <https://github.com/rust-lang/rust/issues/35896>",
+        edition: Some(Edition::Edition2018),
+    };
 }
 
 declare_lint! {
@@ -326,13 +397,21 @@ declare_lint! {
 declare_lint! {
     pub WHERE_CLAUSES_OBJECT_SAFETY,
     Warn,
-    "checks the object safety of where clauses"
+    "checks the object safety of where clauses",
+    @future_incompatible = FutureIncompatibleInfo {
+        reference: "issue #51443 <https://github.com/rust-lang/rust/issues/51443>",
+        edition: None,
+    };
 }
 
 declare_lint! {
     pub PROC_MACRO_DERIVE_RESOLUTION_FALLBACK,
     Warn,
-    "detects proc macro derives using inaccessible names from parent modules"
+    "detects proc macro derives using inaccessible names from parent modules",
+    @future_incompatible = FutureIncompatibleInfo {
+        reference: "issue #50504 <https://github.com/rust-lang/rust/issues/50504>",
+        edition: None,
+    };
 }
 
 declare_lint! {
@@ -346,7 +425,11 @@ declare_lint! {
     pub MACRO_EXPANDED_MACRO_EXPORTS_ACCESSED_BY_ABSOLUTE_PATHS,
     Deny,
     "macro-expanded `macro_export` macros from the current crate \
-     cannot be referred to by absolute paths"
+     cannot be referred to by absolute paths",
+    @future_incompatible = FutureIncompatibleInfo {
+        reference: "issue #52234 <https://github.com/rust-lang/rust/issues/52234>",
+        edition: None,
+    };
 }
 
 declare_lint! {
@@ -359,7 +442,11 @@ declare_lint! {
     pub INDIRECT_STRUCTURAL_MATCH,
     // defaulting to allow until rust-lang/rust#62614 is fixed.
     Allow,
-    "pattern with const indirectly referencing non-`#[structural_match]` type"
+    "pattern with const indirectly referencing non-`#[structural_match]` type",
+    @future_incompatible = FutureIncompatibleInfo {
+        reference: "issue #62411 <https://github.com/rust-lang/rust/issues/62411>",
+        edition: None,
+    };
 }
 
 /// Some lints that are buffered from `libsyntax`. See `syntax::early_buffered_lints`.
@@ -367,7 +454,11 @@ pub mod parser {
     declare_lint! {
         pub ILL_FORMED_ATTRIBUTE_INPUT,
         Warn,
-        "ill-formed attribute inputs that were previously accepted and used in practice"
+        "ill-formed attribute inputs that were previously accepted and used in practice",
+        @future_incompatible = super::FutureIncompatibleInfo {
+            reference: "issue #57571 <https://github.com/rust-lang/rust/issues/57571>",
+            edition: None,
+        };
     }
 
     declare_lint! {
@@ -387,31 +478,47 @@ declare_lint! {
     pub DEPRECATED_IN_FUTURE,
     Allow,
     "detects use of items that will be deprecated in a future version",
-    report_in_external_macro: true
+    report_in_external_macro
 }
 
 declare_lint! {
     pub AMBIGUOUS_ASSOCIATED_ITEMS,
     Deny,
-    "ambiguous associated items"
+    "ambiguous associated items",
+    @future_incompatible = FutureIncompatibleInfo {
+        reference: "issue #57644 <https://github.com/rust-lang/rust/issues/57644>",
+        edition: None,
+    };
 }
 
 declare_lint! {
     pub NESTED_IMPL_TRAIT,
     Warn,
-    "nested occurrence of `impl Trait` type"
+    "nested occurrence of `impl Trait` type",
+    @future_incompatible = FutureIncompatibleInfo {
+        reference: "issue #59014 <https://github.com/rust-lang/rust/issues/59014>",
+        edition: None,
+    };
 }
 
 declare_lint! {
     pub MUTABLE_BORROW_RESERVATION_CONFLICT,
     Warn,
-    "reservation of a two-phased borrow conflicts with other shared borrows"
+    "reservation of a two-phased borrow conflicts with other shared borrows",
+    @future_incompatible = FutureIncompatibleInfo {
+        reference: "issue #59159 <https://github.com/rust-lang/rust/issues/59159>",
+        edition: None,
+    };
 }
 
 declare_lint! {
     pub SOFT_UNSTABLE,
     Deny,
-    "a feature gate that doesn't break dependent crates"
+    "a feature gate that doesn't break dependent crates",
+    @future_incompatible = FutureIncompatibleInfo {
+        reference: "issue #64266 <https://github.com/rust-lang/rust/issues/64266>",
+        edition: None,
+    };
 }
 
 declare_lint_pass! {

src/librustc/lint/context.rs

@@ -22,11 +22,11 @@ use crate::hir::intravisit as hir_visit;
 use crate::hir::intravisit::Visitor;
 use crate::hir::map::{definitions::DisambiguatedDefPathData, DefPathData};
 use crate::lint::{EarlyLintPass, LateLintPass, EarlyLintPassObject, LateLintPassObject};
-use crate::lint::{LintArray, Level, Lint, LintId, LintPass, LintBuffer};
+use crate::lint::{Level, Lint, LintId, LintPass, LintBuffer, FutureIncompatibleInfo};
 use crate::lint::builtin::BuiltinLintDiagnostics;
 use crate::lint::levels::{LintLevelSets, LintLevelsBuilder};
 use crate::middle::privacy::AccessLevels;
-use crate::session::{config, early_error, Session};
+use crate::session::Session;
 use crate::ty::{self, print::Printer, subst::GenericArg, TyCtxt, Ty};
 use crate::ty::layout::{LayoutError, LayoutOf, TyLayout};
 use crate::util::nodemap::FxHashMap;
@@ -35,10 +35,9 @@ use crate::util::common::time;
 use errors::DiagnosticBuilder;
 use std::slice;
 use std::default::Default as StdDefault;
-use rustc_data_structures::sync::{ReadGuard, Lock, ParallelIterator, join, par_iter};
+use rustc_data_structures::sync::{self, ParallelIterator, join, par_iter};
 use rustc_serialize::{Decoder, Decodable, Encoder, Encodable};
 use syntax::ast;
-use syntax::edition;
 use syntax::util::lev_distance::find_best_match_for_name;
 use syntax::visit as ast_visit;
 use syntax_pos::{MultiSpan, Span, symbol::Symbol};
@@ -50,24 +49,25 @@ use syntax_pos::{MultiSpan, Span, symbol::Symbol};
 pub struct LintStore {
     /// Registered lints. The bool is true if the lint was
     /// added by a plugin.
-    lints: Vec<(&'static Lint, bool)>,
+    lints: Vec<&'static Lint>,
 
-    /// Trait objects for each lint pass.
-    /// This is only `None` while performing a lint pass.
-    pre_expansion_passes: Option<Vec<EarlyLintPassObject>>,
-    early_passes: Option<Vec<EarlyLintPassObject>>,
-    late_passes: Lock<Option<Vec<LateLintPassObject>>>,
-    late_module_passes: Vec<LateLintPassObject>,
+    /// Constructor functions for each variety of lint pass.
+    ///
+    /// These should only be called once, but since we want to avoid locks or
+    /// interior mutability, we don't enforce this (and lints should, in theory,
+    /// be compatible with being constructed more than once, though not
+    /// necessarily in a sane manner. This is safe though.)
+    pre_expansion_passes: Vec<Box<dyn Fn() -> EarlyLintPassObject + sync::Send + sync::Sync>>,
+    early_passes: Vec<Box<dyn Fn() -> EarlyLintPassObject + sync::Send + sync::Sync>>,
+    late_passes: Vec<Box<dyn Fn() -> LateLintPassObject + sync::Send + sync::Sync>>,
+    /// This is unique in that we construct them per-module, so not once.
+    late_module_passes: Vec<Box<dyn Fn() -> LateLintPassObject + sync::Send + sync::Sync>>,
 
     /// Lints indexed by name.
     by_name: FxHashMap<String, TargetLint>,
 
     /// Map of registered lint groups to what lints they expand to.
     lint_groups: FxHashMap<&'static str, LintGroup>,
-
-    /// Extra info for future incompatibility lints, describing the
-    /// issue or RFC that caused the incompatibility.
-    future_incompatible: FxHashMap<LintId, FutureIncompatibleInfo>,
 }
 
 /// Lints that are buffered up early on in the `Session` before the
@@ -81,18 +81,6 @@ pub struct BufferedEarlyLint {
     pub diagnostic: BuiltinLintDiagnostics,
 }
 
-/// Extra information for a future incompatibility lint. See the call
-/// to `register_future_incompatible` in `librustc_lint/lib.rs` for
-/// guidelines.
-pub struct FutureIncompatibleInfo {
-    pub id: LintId,
-    /// e.g., a URL for an issue/PR/RFC or error code
-    pub reference: &'static str,
-    /// If this is an edition fixing lint, the edition in which
-    /// this lint becomes obsolete
-    pub edition: Option<edition::Edition>,
-}
-
 /// The target of the `by_name` map, which accounts for renaming/deprecation.
 enum TargetLint {
     /// A direct lint target
@@ -142,17 +130,16 @@ impl LintStore {
     pub fn new() -> LintStore {
         LintStore {
             lints: vec![],
-            pre_expansion_passes: Some(vec![]),
-            early_passes: Some(vec![]),
-            late_passes: Lock::new(Some(vec![])),
+            pre_expansion_passes: vec![],
+            early_passes: vec![],
+            late_passes: vec![],
             late_module_passes: vec![],
             by_name: Default::default(),
-            future_incompatible: Default::default(),
             lint_groups: Default::default(),
         }
     }
 
-    pub fn get_lints<'t>(&'t self) -> &'t [(&'static Lint, bool)] {
+    pub fn get_lints<'t>(&'t self) -> &'t [&'static Lint] {
         &self.lints
     }
 
@@ -168,101 +155,66 @@ impl LintStore {
             .collect()
     }
 
-    pub fn register_early_pass(&mut self,
-                               sess: Option<&Session>,
-                               from_plugin: bool,
-                               register_only: bool,
-                               pass: EarlyLintPassObject) {
-        self.push_pass(sess, from_plugin, &pass);
-        if !register_only {
-            self.early_passes.as_mut().unwrap().push(pass);
-        }
+    pub fn register_early_pass(
+        &mut self,
+        pass: impl Fn() -> EarlyLintPassObject + 'static + sync::Send + sync::Sync
+    ) {
+        self.early_passes.push(Box::new(pass));
     }
 
     pub fn register_pre_expansion_pass(
         &mut self,
-        sess: Option<&Session>,
-        from_plugin: bool,
-        register_only: bool,
-        pass: EarlyLintPassObject,
+        pass: impl Fn() -> EarlyLintPassObject + 'static + sync::Send + sync::Sync,
     ) {
-        self.push_pass(sess, from_plugin, &pass);
-        if !register_only {
-            self.pre_expansion_passes.as_mut().unwrap().push(pass);
-        }
+        self.pre_expansion_passes.push(Box::new(pass));
     }
 
-    pub fn register_late_pass(&mut self,
-                              sess: Option<&Session>,
-                              from_plugin: bool,
-                              register_only: bool,
-                              per_module: bool,
-                              pass: LateLintPassObject) {
-        self.push_pass(sess, from_plugin, &pass);
-        if !register_only {
-            if per_module {
-                self.late_module_passes.push(pass);
-            } else {
-                self.late_passes.lock().as_mut().unwrap().push(pass);
-            }
-        }
+    pub fn register_late_pass(
+        &mut self,
+        pass: impl Fn() -> LateLintPassObject + 'static + sync::Send + sync::Sync,
+    ) {
+        self.late_passes.push(Box::new(pass));
+    }
+
+    pub fn register_late_mod_pass(
+        &mut self,
+        pass: impl Fn() -> LateLintPassObject + 'static + sync::Send + sync::Sync,
+    ) {
+        self.late_module_passes.push(Box::new(pass));
     }
 
     // Helper method for register_early/late_pass
-    fn push_pass<P: LintPass + ?Sized + 'static>(&mut self,
-                                        sess: Option<&Session>,
-                                        from_plugin: bool,
-                                        pass: &Box<P>) {
-        for lint in pass.get_lints() {
-            self.lints.push((lint, from_plugin));
+    pub fn register_lints(&mut self, lints: &[&'static Lint]) {
+        for lint in lints {
+            self.lints.push(lint);
 
             let id = LintId::of(lint);
             if self.by_name.insert(lint.name_lower(), Id(id)).is_some() {
-                let msg = format!("duplicate specification of lint {}", lint.name_lower());
-                match (sess, from_plugin) {
-                    // We load builtin lints first, so a duplicate is a compiler bug.
-                    // Use early_error when handling -W help with no crate.
-                    (None, _) => early_error(config::ErrorOutputType::default(), &msg[..]),
-                    (Some(_), false) => bug!("{}", msg),
+                bug!("duplicate specification of lint {}", lint.name_lower())
+            }
 
-                    // A duplicate name from a plugin is a user error.
-                    (Some(sess), true)  => sess.err(&msg[..]),
+            if let Some(FutureIncompatibleInfo { edition, .. }) = lint.future_incompatible {
+                if let Some(edition) = edition {
+                    self.lint_groups.entry(edition.lint_name())
+                        .or_insert(LintGroup {
+                            lint_ids: vec![],
+                            from_plugin: lint.is_plugin,
+                            depr: None,
+                        })
+                        .lint_ids.push(id);
                 }
+
+                self.lint_groups.entry("future_incompatible")
+                    .or_insert(LintGroup {
+                        lint_ids: vec![],
+                        from_plugin: lint.is_plugin,
+                        depr: None,
+                    })
+                    .lint_ids.push(id);
             }
         }
     }
 
-    pub fn register_future_incompatible(&mut self,
-                                        sess: Option<&Session>,
-                                        lints: Vec<FutureIncompatibleInfo>) {
-
-        for edition in edition::ALL_EDITIONS {
-            let lints = lints.iter().filter(|f| f.edition == Some(*edition)).map(|f| f.id)
-                             .collect::<Vec<_>>();
-            if !lints.is_empty() {
-                self.register_group(sess, false, edition.lint_name(), None, lints)
-            }
-        }
-
-        let mut future_incompatible = Vec::with_capacity(lints.len());
-        for lint in lints {
-            future_incompatible.push(lint.id);
-            self.future_incompatible.insert(lint.id, lint);
-        }
-
-        self.register_group(
-            sess,
-            false,
-            "future_incompatible",
-            None,
-            future_incompatible,
-        );
-    }
-
-    pub fn future_incompatible(&self, id: LintId) -> Option<&FutureIncompatibleInfo> {
-        self.future_incompatible.get(&id)
-    }
-
     pub fn register_group_alias(
         &mut self,
         lint_name: &'static str,
@@ -277,7 +229,6 @@ impl LintStore {
 
     pub fn register_group(
         &mut self,
-        sess: Option<&Session>,
         from_plugin: bool,
         name: &'static str,
         deprecated_name: Option<&'static str>,
@@ -300,16 +251,7 @@ impl LintStore {
         }
 
         if !new {
-            let msg = format!("duplicate specification of lint group {}", name);
-            match (sess, from_plugin) {
-                // We load builtin lints first, so a duplicate is a compiler bug.
-                // Use early_error when handling -W help with no crate.
-                (None, _) => early_error(config::ErrorOutputType::default(), &msg[..]),
-                (Some(_), false) => bug!("{}", msg),
-
-                // A duplicate name from a plugin is a user error.
-                (Some(sess), true)  => sess.err(&msg[..]),
-            }
+            bug!("duplicate specification of lint group {}", name);
         }
     }
 
@@ -522,7 +464,7 @@ pub struct LateContext<'a, 'tcx> {
     pub access_levels: &'a AccessLevels,
 
     /// The store of registered lints and the lint levels.
-    lint_store: ReadGuard<'a, LintStore>,
+    lint_store: &'tcx LintStore,
 
     last_node_with_lint_attrs: hir::HirId,
 
@@ -550,7 +492,7 @@ pub struct EarlyContext<'a> {
     builder: LintLevelsBuilder<'a>,
 
     /// The store of registered lints and the lint levels.
-    lint_store: ReadGuard<'a, LintStore>,
+    lint_store: &'a LintStore,
 
     buffered: LintBuffer,
 }
@@ -639,14 +581,15 @@ pub trait LintContext: Sized {
 impl<'a> EarlyContext<'a> {
     fn new(
         sess: &'a Session,
+        lint_store: &'a LintStore,
         krate: &'a ast::Crate,
         buffered: LintBuffer,
     ) -> EarlyContext<'a> {
         EarlyContext {
             sess,
             krate,
-            lint_store: sess.lint_store.borrow(),
-            builder: LintLevelSets::builder(sess),
+            lint_store,
+            builder: LintLevelSets::builder(sess, lint_store),
             buffered,
         }
     }
@@ -681,7 +624,7 @@ impl<'a, T: EarlyLintPass> EarlyContextAndPass<'a, T> {
                           f: F)
         where F: FnOnce(&mut Self)
     {
-        let push = self.context.builder.push(attrs);
+        let push = self.context.builder.push(attrs, &self.context.lint_store);
         self.check_id(id);
         self.enter_attrs(attrs);
         f(self);
@@ -875,7 +818,7 @@ impl<'a, 'tcx> LateContext<'a, 'tcx> {
                     _ => {}
                 }
 
-                path.push(disambiguated_data.data.as_interned_str().as_symbol());
+                path.push(disambiguated_data.data.as_symbol());
                 Ok(path)
             }
 
@@ -1355,10 +1298,6 @@ impl LintPass for LateLintPassObjects<'_> {
     fn name(&self) -> &'static str {
         panic!()
     }
-
-    fn get_lints(&self) -> LintArray {
-        panic!()
-    }
 }
 
 macro_rules! expand_late_lint_pass_impl_methods {
@@ -1393,7 +1332,7 @@ fn late_lint_mod_pass<'tcx, T: for<'a> LateLintPass<'a, 'tcx>>(
         tables: &ty::TypeckTables::empty(None),
         param_env: ty::ParamEnv::empty(),
         access_levels,
-        lint_store: tcx.sess.lint_store.borrow(),
+        lint_store: &tcx.lint_store,
         last_node_with_lint_attrs: tcx.hir().as_local_hir_id(module_def_id).unwrap(),
         generics: None,
         only_module: true,
@@ -1425,8 +1364,8 @@ pub fn late_lint_mod<'tcx, T: for<'a> LateLintPass<'a, 'tcx>>(
 
     late_lint_mod_pass(tcx, module_def_id, builtin_lints);
 
-    let mut passes: Vec<_> = tcx.sess.lint_store.borrow().late_module_passes
-                                .iter().map(|pass| pass.fresh_late_pass()).collect();
+    let mut passes: Vec<_> = tcx.lint_store.late_module_passes
+                                .iter().map(|pass| (pass)()).collect();
 
     if !passes.is_empty() {
         late_lint_mod_pass(tcx, module_def_id, LateLintPassObjects { lints: &mut passes[..] });
@@ -1443,7 +1382,7 @@ fn late_lint_pass_crate<'tcx, T: for<'a> LateLintPass<'a, 'tcx>>(tcx: TyCtxt<'tc
         tables: &ty::TypeckTables::empty(None),
         param_env: ty::ParamEnv::empty(),
         access_levels,
-        lint_store: tcx.sess.lint_store.borrow(),
+        lint_store: &tcx.lint_store,
         last_node_with_lint_attrs: hir::CRATE_HIR_ID,
         generics: None,
         only_module: false,
@@ -1467,7 +1406,8 @@ fn late_lint_pass_crate<'tcx, T: for<'a> LateLintPass<'a, 'tcx>>(tcx: TyCtxt<'tc
 }
 
 fn late_lint_crate<'tcx, T: for<'a> LateLintPass<'a, 'tcx>>(tcx: TyCtxt<'tcx>, builtin_lints: T) {
-    let mut passes = tcx.sess.lint_store.borrow().late_passes.lock().take().unwrap();
+    let mut passes = tcx.lint_store
+        .late_passes.iter().map(|p| (p)()).collect::<Vec<_>>();
 
     if !tcx.sess.opts.debugging_opts.no_interleave_lints {
         if !passes.is_empty() {
@@ -1482,8 +1422,8 @@ fn late_lint_crate<'tcx, T: for<'a> LateLintPass<'a, 'tcx>>(tcx: TyCtxt<'tcx>, b
             });
         }
 
-        let mut passes: Vec<_> = tcx.sess.lint_store.borrow().late_module_passes
-                                    .iter().map(|pass| pass.fresh_late_pass()).collect();
+        let mut passes: Vec<_> = tcx.lint_store.late_module_passes
+                                    .iter().map(|pass| (pass)()).collect();
 
         for pass in &mut passes {
             time(tcx.sess, &format!("running late module lint: {}", pass.name()), || {
@@ -1491,9 +1431,6 @@ fn late_lint_crate<'tcx, T: for<'a> LateLintPass<'a, 'tcx>>(tcx: TyCtxt<'tcx>, b
             });
         }
     }
-
-    // Put the passes back in the session.
-    *tcx.sess.lint_store.borrow().late_passes.lock() = Some(passes);
 }
 
 /// Performs lint checking on a crate.
@@ -1525,10 +1462,6 @@ impl LintPass for EarlyLintPassObjects<'_> {
     fn name(&self) -> &'static str {
         panic!()
     }
-
-    fn get_lints(&self) -> LintArray {
-        panic!()
-    }
 }
 
 macro_rules! expand_early_lint_pass_impl_methods {
@@ -1553,12 +1486,13 @@ early_lint_methods!(early_lint_pass_impl, []);
 
 fn early_lint_crate<T: EarlyLintPass>(
     sess: &Session,
+    lint_store: &LintStore,
     krate: &ast::Crate,
     pass: T,
     buffered: LintBuffer,
 ) -> LintBuffer {
     let mut cx = EarlyContextAndPass {
-        context: EarlyContext::new(sess, krate, buffered),
+        context: EarlyContext::new(sess, lint_store, krate, buffered),
         pass,
     };
 
@@ -1577,28 +1511,30 @@ fn early_lint_crate<T: EarlyLintPass>(
 
 pub fn check_ast_crate<T: EarlyLintPass>(
     sess: &Session,
+    lint_store: &LintStore,
     krate: &ast::Crate,
     pre_expansion: bool,
     builtin_lints: T,
 ) {
-    let (mut passes, mut buffered) = if pre_expansion {
+    let (mut passes, mut buffered): (Vec<_>, _) = if pre_expansion {
         (
-            sess.lint_store.borrow_mut().pre_expansion_passes.take().unwrap(),
+            lint_store.pre_expansion_passes.iter().map(|p| (p)()).collect(),
             LintBuffer::default(),
         )
     } else {
         (
-            sess.lint_store.borrow_mut().early_passes.take().unwrap(),
+            lint_store.early_passes.iter().map(|p| (p)()).collect(),
             sess.buffered_lints.borrow_mut().take().unwrap(),
         )
     };
 
     if !sess.opts.debugging_opts.no_interleave_lints {
-        buffered = early_lint_crate(sess, krate, builtin_lints, buffered);
+        buffered = early_lint_crate(sess, lint_store, krate, builtin_lints, buffered);
 
         if !passes.is_empty() {
             buffered = early_lint_crate(
                 sess,
+                lint_store,
                 krate,
                 EarlyLintPassObjects { lints: &mut passes[..] },
                 buffered,
@@ -1609,6 +1545,7 @@ pub fn check_ast_crate<T: EarlyLintPass>(
             buffered = time(sess, &format!("running lint: {}", pass.name()), || {
                 early_lint_crate(
                     sess,
+                    lint_store,
                     krate,
                     EarlyLintPassObjects { lints: slice::from_mut(pass) },
                     buffered,
@@ -1617,13 +1554,6 @@ pub fn check_ast_crate<T: EarlyLintPass>(
         }
     }
 
-    // Put the lint store levels and passes back in the session.
-    if pre_expansion {
-        sess.lint_store.borrow_mut().pre_expansion_passes = Some(passes);
-    } else {
-        sess.lint_store.borrow_mut().early_passes = Some(passes);
-    }
-
     // All of the buffered lints should have been emitted at this point.
     // If not, that means that we somehow buffered a lint for a node id
     // that was not lint-checked (perhaps it doesn't exist?). This is a bug.
@@ -1653,7 +1583,7 @@ impl Decodable for LintId {
     fn decode<D: Decoder>(d: &mut D) -> Result<LintId, D::Error> {
         let s = d.read_str()?;
         ty::tls::with(|tcx| {
-            match tcx.sess.lint_store.borrow().find_lints(&s) {
+            match tcx.lint_store.find_lints(&s) {
                 Ok(ids) => {
                     if ids.len() != 0 {
                         panic!("invalid lint-id `{}`", s);

src/librustc/lint/levels.rs

@@ -3,7 +3,7 @@ use std::cmp;
 use crate::hir::HirId;
 use crate::ich::StableHashingContext;
 use crate::lint::builtin;
-use crate::lint::context::CheckLintNameResult;
+use crate::lint::context::{LintStore, CheckLintNameResult};
 use crate::lint::{self, Lint, LintId, Level, LintSource};
 use crate::session::Session;
 use crate::util::nodemap::FxHashMap;
@@ -35,21 +35,20 @@ enum LintSet {
 }
 
 impl LintLevelSets {
-    pub fn new(sess: &Session) -> LintLevelSets {
+    pub fn new(sess: &Session, lint_store: &LintStore) -> LintLevelSets {
         let mut me = LintLevelSets {
             list: Vec::new(),
             lint_cap: Level::Forbid,
         };
-        me.process_command_line(sess);
+        me.process_command_line(sess, lint_store);
         return me
     }
 
-    pub fn builder(sess: &Session) -> LintLevelsBuilder<'_> {
-        LintLevelsBuilder::new(sess, LintLevelSets::new(sess))
+    pub fn builder<'a>(sess: &'a Session, store: &LintStore) -> LintLevelsBuilder<'a> {
+        LintLevelsBuilder::new(sess, LintLevelSets::new(sess, store))
     }
 
-    fn process_command_line(&mut self, sess: &Session) {
-        let store = sess.lint_store.borrow();
+    fn process_command_line(&mut self, sess: &Session, store: &LintStore) {
         let mut specs = FxHashMap::default();
         self.lint_cap = sess.opts.lint_cap.unwrap_or(Level::Forbid);
 
@@ -186,9 +185,8 @@ impl<'a> LintLevelsBuilder<'a> {
     ///   #[allow]
     ///
     /// Don't forget to call `pop`!
-    pub fn push(&mut self, attrs: &[ast::Attribute]) -> BuilderPush {
+    pub fn push(&mut self, attrs: &[ast::Attribute], store: &LintStore) -> BuilderPush {
         let mut specs = FxHashMap::default();
-        let store = self.sess.lint_store.borrow();
         let sess = self.sess;
         let bad_attr = |span| {
             struct_span_err!(sess, span, E0452, "malformed lint attribute input")

src/librustc/lint/mod.rs

@@ -45,7 +45,7 @@ use syntax_pos::Span;
 
 pub use crate::lint::context::{LateContext, EarlyContext, LintContext, LintStore,
                         check_crate, check_ast_crate, late_lint_mod, CheckLintNameResult,
-                        FutureIncompatibleInfo, BufferedEarlyLint,};
+                        BufferedEarlyLint,};
 
 /// Specification of a single lint.
 #[derive(Copy, Clone, Debug)]
@@ -76,9 +76,35 @@ pub struct Lint {
 
     /// `true` if this lint is reported even inside expansions of external macros.
     pub report_in_external_macro: bool,
+
+    pub future_incompatible: Option<FutureIncompatibleInfo>,
+
+    pub is_plugin: bool,
+}
+
+/// Extra information for a future incompatibility lint.
+#[derive(Copy, Clone, Debug)]
+pub struct FutureIncompatibleInfo {
+    /// e.g., a URL for an issue/PR/RFC or error code
+    pub reference: &'static str,
+    /// If this is an edition fixing lint, the edition in which
+    /// this lint becomes obsolete
+    pub edition: Option<Edition>,
 }
 
 impl Lint {
+    pub const fn default_fields_for_macro() -> Self {
+        Lint {
+            name: "",
+            default_level: Level::Forbid,
+            desc: "",
+            edition_lint_opts: None,
+            is_plugin: false,
+            report_in_external_macro: false,
+            future_incompatible: None,
+        }
+    }
+
     /// Returns the `rust::lint::Lint` for a `syntax::early_buffered_lints::BufferedEarlyLintId`.
     pub fn from_parser_lint_id(lint_id: BufferedEarlyLintId) -> &'static Self {
         match lint_id {
@@ -105,18 +131,21 @@ impl Lint {
 #[macro_export]
 macro_rules! declare_lint {
     ($vis: vis $NAME: ident, $Level: ident, $desc: expr) => (
-        declare_lint!{$vis $NAME, $Level, $desc, false}
+        declare_lint!(
+            $vis $NAME, $Level, $desc,
+        );
     );
-    ($vis: vis $NAME: ident, $Level: ident, $desc: expr, report_in_external_macro: $rep: expr) => (
-        declare_lint!{$vis $NAME, $Level, $desc, $rep}
-    );
-    ($vis: vis $NAME: ident, $Level: ident, $desc: expr, $external: expr) => (
+    ($vis: vis $NAME: ident, $Level: ident, $desc: expr,
+     $(@future_incompatible = $fi:expr;)? $($v:ident),*) => (
         $vis static $NAME: &$crate::lint::Lint = &$crate::lint::Lint {
             name: stringify!($NAME),
             default_level: $crate::lint::$Level,
             desc: $desc,
             edition_lint_opts: None,
-            report_in_external_macro: $external,
+            is_plugin: false,
+            $($v: true,)*
+            $(future_incompatible: Some($fi),)*
+            ..$crate::lint::Lint::default_fields_for_macro()
         };
     );
     ($vis: vis $NAME: ident, $Level: ident, $desc: expr,
@@ -128,6 +157,7 @@ macro_rules! declare_lint {
             desc: $desc,
             edition_lint_opts: Some(($lint_edition, $crate::lint::Level::$edition_level)),
             report_in_external_macro: false,
+            is_plugin: false,
         };
     );
 }
@@ -156,6 +186,8 @@ macro_rules! declare_tool_lint {
             desc: $desc,
             edition_lint_opts: None,
             report_in_external_macro: $external,
+            future_incompatible: None,
+            is_plugin: true,
         };
     );
 }
@@ -173,14 +205,6 @@ pub type LintArray = Vec<&'static Lint>;
 
 pub trait LintPass {
     fn name(&self) -> &'static str;
-
-    /// Gets descriptions of the lints this `LintPass` object can emit.
-    ///
-    /// N.B., there is no enforcement that the object only emits lints it registered.
-    /// And some `rustc` internal `LintPass`es register lints to be emitted by other
-    /// parts of the compiler. If you want enforced access restrictions for your
-    /// `Lint`, make it a private `static` item in its own module.
-    fn get_lints(&self) -> LintArray;
 }
 
 /// Implements `LintPass for $name` with the given list of `Lint` statics.
@@ -189,7 +213,9 @@ macro_rules! impl_lint_pass {
     ($name:ident => [$($lint:expr),* $(,)?]) => {
         impl LintPass for $name {
             fn name(&self) -> &'static str { stringify!($name) }
-            fn get_lints(&self) -> LintArray { $crate::lint_array!($($lint),*) }
+        }
+        impl $name {
+            pub fn get_lints() -> LintArray { $crate::lint_array!($($lint),*) }
         }
     };
 }
@@ -287,9 +313,6 @@ macro_rules! expand_lint_pass_methods {
 macro_rules! declare_late_lint_pass {
     ([], [$hir:tt], [$($methods:tt)*]) => (
         pub trait LateLintPass<'a, $hir>: LintPass {
-            fn fresh_late_pass(&self) -> LateLintPassObject {
-                panic!()
-            }
             expand_lint_pass_methods!(&LateContext<'a, $hir>, [$($methods)*]);
         }
     )
@@ -327,6 +350,12 @@ macro_rules! declare_combined_late_lint_pass {
                     $($passes: $constructor,)*
                 }
             }
+
+            $v fn get_lints() -> LintArray {
+                let mut lints = Vec::new();
+                $(lints.extend_from_slice(&$passes::get_lints());)*
+                lints
+            }
         }
 
         impl<'a, 'tcx> LateLintPass<'a, 'tcx> for $name {
@@ -337,12 +366,6 @@ macro_rules! declare_combined_late_lint_pass {
             fn name(&self) -> &'static str {
                 panic!()
             }
-
-            fn get_lints(&self) -> LintArray {
-                let mut lints = Vec::new();
-                $(lints.extend_from_slice(&self.$passes.get_lints());)*
-                lints
-            }
         }
     )
 }
@@ -454,6 +477,12 @@ macro_rules! declare_combined_early_lint_pass {
                     $($passes: $constructor,)*
                 }
             }
+
+            $v fn get_lints() -> LintArray {
+                let mut lints = Vec::new();
+                $(lints.extend_from_slice(&$passes::get_lints());)*
+                lints
+            }
         }
 
         impl EarlyLintPass for $name {
@@ -464,12 +493,6 @@ macro_rules! declare_combined_early_lint_pass {
             fn name(&self) -> &'static str {
                 panic!()
             }
-
-            fn get_lints(&self) -> LintArray {
-                let mut lints = Vec::new();
-                $(lints.extend_from_slice(&self.$passes.get_lints());)*
-                lints
-            }
         }
     )
 }
@@ -649,9 +672,8 @@ pub fn struct_lint_level<'a>(sess: &'a Session,
     };
 
     // Check for future incompatibility lints and issue a stronger warning.
-    let lints = sess.lint_store.borrow();
     let lint_id = LintId::of(lint);
-    let future_incompatible = lints.future_incompatible(lint_id);
+    let future_incompatible = lint.future_incompatible;
 
     // If this code originates in a foreign macro, aka something that this crate
     // did not itself author, then it's likely that there's nothing this crate
@@ -755,13 +777,15 @@ pub fn maybe_lint_level_root(tcx: TyCtxt<'_>, id: hir::HirId) -> bool {
 
 fn lint_levels(tcx: TyCtxt<'_>, cnum: CrateNum) -> &LintLevelMap {
     assert_eq!(cnum, LOCAL_CRATE);
+    let store = &tcx.lint_store;
     let mut builder = LintLevelMapBuilder {
-        levels: LintLevelSets::builder(tcx.sess),
+        levels: LintLevelSets::builder(tcx.sess, &store),
         tcx: tcx,
+        store: store,
     };
     let krate = tcx.hir().krate();
 
-    let push = builder.levels.push(&krate.attrs);
+    let push = builder.levels.push(&krate.attrs, &store);
     builder.levels.register_id(hir::CRATE_HIR_ID);
     for macro_def in &krate.exported_macros {
        builder.levels.register_id(macro_def.hir_id);
@@ -772,19 +796,20 @@ fn lint_levels(tcx: TyCtxt<'_>, cnum: CrateNum) -> &LintLevelMap {
     tcx.arena.alloc(builder.levels.build_map())
 }
 
-struct LintLevelMapBuilder<'tcx> {
+struct LintLevelMapBuilder<'a, 'tcx> {
     levels: levels::LintLevelsBuilder<'tcx>,
     tcx: TyCtxt<'tcx>,
+    store: &'a LintStore,
 }
 
-impl LintLevelMapBuilder<'tcx> {
+impl LintLevelMapBuilder<'_, '_> {
     fn with_lint_attrs<F>(&mut self,
                           id: hir::HirId,
                           attrs: &[ast::Attribute],
                           f: F)
         where F: FnOnce(&mut Self)
     {
-        let push = self.levels.push(attrs);
+        let push = self.levels.push(attrs, self.store);
         if push.changed {
             self.levels.register_id(id);
         }
@@ -793,7 +818,7 @@ impl LintLevelMapBuilder<'tcx> {
     }
 }
 
-impl intravisit::Visitor<'tcx> for LintLevelMapBuilder<'tcx> {
+impl intravisit::Visitor<'tcx> for LintLevelMapBuilder<'_, 'tcx> {
     fn nested_visit_map<'this>(&'this mut self) -> intravisit::NestedVisitorMap<'this, 'tcx> {
         intravisit::NestedVisitorMap::All(&self.tcx.hir())
     }

src/librustc/mir/interpret/allocation.rs

@@ -353,11 +353,14 @@ impl<'tcx, Tag: Copy, Extra: AllocationExtra<Tag>> Allocation<Tag, Extra> {
         &mut self,
         cx: &impl HasDataLayout,
         ptr: Pointer<Tag>,
-        src: impl IntoIterator<Item=u8, IntoIter: iter::ExactSizeIterator>,
+        src: impl IntoIterator<Item=u8>,
     ) -> InterpResult<'tcx>
     {
         let mut src = src.into_iter();
-        let bytes = self.get_bytes_mut(cx, ptr, Size::from_bytes(src.len() as u64))?;
+        let (lower, upper) = src.size_hint();
+        let len = upper.expect("can only write bounded iterators");
+        assert_eq!(lower, len, "can only write iterators with a precise length");
+        let bytes = self.get_bytes_mut(cx, ptr, Size::from_bytes(len as u64))?;
         // `zip` would stop when the first iterator ends; we want to definitely
         // cover all of `bytes`.
         for dest in bytes {

src/librustc/mir/mod.rs

@@ -37,7 +37,7 @@ use std::slice;
 use std::vec::IntoIter;
 use std::{iter, mem, option, u32};
 use syntax::ast::Name;
-use syntax::symbol::{InternedString, Symbol};
+use syntax::symbol::Symbol;
 use syntax_pos::{Span, DUMMY_SP};
 
 pub use crate::mir::interpret::AssertMessage;
@@ -2736,8 +2736,8 @@ pub enum UnsafetyViolationKind {
 #[derive(Copy, Clone, PartialEq, RustcEncodable, RustcDecodable, HashStable)]
 pub struct UnsafetyViolation {
     pub source_info: SourceInfo,
-    pub description: InternedString,
-    pub details: InternedString,
+    pub description: Symbol,
+    pub details: Symbol,
     pub kind: UnsafetyViolationKind,
 }
 

src/librustc/mir/mono.rs

@@ -1,6 +1,6 @@
 use crate::hir::def_id::{DefId, CrateNum, LOCAL_CRATE};
 use crate::hir::HirId;
-use syntax::symbol::InternedString;
+use syntax::symbol::Symbol;
 use syntax::attr::InlineAttr;
 use syntax::source_map::Span;
 use crate::ty::{Instance, InstanceDef, TyCtxt, SymbolName, subst::InternalSubsts};
@@ -80,7 +80,7 @@ impl<'tcx> MonoItem<'tcx> {
             MonoItem::GlobalAsm(hir_id) => {
                 let def_id = tcx.hir().local_def_id(hir_id);
                 SymbolName {
-                    name: InternedString::intern(&format!("global_asm_{:?}", def_id))
+                    name: Symbol::intern(&format!("global_asm_{:?}", def_id))
                 }
             }
         }
@@ -246,7 +246,7 @@ pub struct CodegenUnit<'tcx> {
     /// name be unique amongst **all** crates. Therefore, it should
     /// contain something unique to this crate (e.g., a module path)
     /// as well as the crate name and disambiguator.
-    name: InternedString,
+    name: Symbol,
     items: FxHashMap<MonoItem<'tcx>, (Linkage, Visibility)>,
     size_estimate: Option<usize>,
 }
@@ -294,7 +294,7 @@ impl_stable_hash_for!(enum self::Visibility {
 });
 
 impl<'tcx> CodegenUnit<'tcx> {
-    pub fn new(name: InternedString) -> CodegenUnit<'tcx> {
+    pub fn new(name: Symbol) -> CodegenUnit<'tcx> {
         CodegenUnit {
             name: name,
             items: Default::default(),
@@ -302,11 +302,11 @@ impl<'tcx> CodegenUnit<'tcx> {
         }
     }
 
-    pub fn name(&self) -> &InternedString {
-        &self.name
+    pub fn name(&self) -> Symbol {
+        self.name
     }
 
-    pub fn set_name(&mut self, name: InternedString) {
+    pub fn set_name(&mut self, name: Symbol) {
         self.name = name;
     }
 
@@ -474,7 +474,7 @@ impl CodegenUnitNameBuilder<'tcx> {
                                    cnum: CrateNum,
                                    components: I,
                                    special_suffix: Option<S>)
-                                   -> InternedString
+                                   -> Symbol
         where I: IntoIterator<Item=C>,
               C: fmt::Display,
               S: fmt::Display,
@@ -487,7 +487,7 @@ impl CodegenUnitNameBuilder<'tcx> {
             cgu_name
         } else {
             let cgu_name = &cgu_name.as_str()[..];
-            InternedString::intern(&CodegenUnit::mangle_name(cgu_name))
+            Symbol::intern(&CodegenUnit::mangle_name(cgu_name))
         }
     }
 
@@ -497,7 +497,7 @@ impl CodegenUnitNameBuilder<'tcx> {
                                              cnum: CrateNum,
                                              components: I,
                                              special_suffix: Option<S>)
-                                             -> InternedString
+                                             -> Symbol
         where I: IntoIterator<Item=C>,
               C: fmt::Display,
               S: fmt::Display,
@@ -543,6 +543,6 @@ impl CodegenUnitNameBuilder<'tcx> {
             write!(cgu_name, ".{}", special_suffix).unwrap();
         }
 
-        InternedString::intern(&cgu_name[..])
+        Symbol::intern(&cgu_name[..])
     }
 }

src/librustc/query/mod.rs

@@ -15,7 +15,7 @@ use crate::traits::query::{
 };
 
 use std::borrow::Cow;
-use syntax_pos::symbol::InternedString;
+use syntax_pos::symbol::Symbol;
 
 // Each of these queries corresponds to a function pointer field in the
 // `Providers` struct for requesting a value of that type, and a method
@@ -924,7 +924,7 @@ rustc_queries! {
             desc { "collect_and_partition_mono_items" }
         }
         query is_codegened_item(_: DefId) -> bool {}
-        query codegen_unit(_: InternedString) -> Arc<CodegenUnit<'tcx>> {
+        query codegen_unit(_: Symbol) -> Arc<CodegenUnit<'tcx>> {
             no_force
             desc { "codegen_unit" }
         }

src/librustc/session/mod.rs

@@ -14,7 +14,7 @@ use crate::util::common::{duration_to_secs_str, ErrorReported};
 
 use rustc_data_structures::base_n;
 use rustc_data_structures::sync::{
-    self, Lrc, Lock, OneThread, Once, RwLock, AtomicU64, AtomicUsize, Ordering,
+    self, Lrc, Lock, OneThread, Once, AtomicU64, AtomicUsize, Ordering,
     Ordering::SeqCst,
 };
 
@@ -77,9 +77,11 @@ pub struct Session {
     /// if the value stored here has been affected by path remapping.
     pub working_dir: (PathBuf, bool),
 
-    // FIXME: `lint_store` and `buffered_lints` are not thread-safe,
-    // but are only used in a single thread.
-    pub lint_store: RwLock<lint::LintStore>,
+    /// This is intended to be used from a single thread.
+    ///
+    /// FIXME: there was a previous comment about this not being thread safe,
+    /// but it's not clear how or why that's the case. The LintBuffer itself is certainly thread
+    /// safe at least from a "Rust safety" standpoint.
     pub buffered_lints: Lock<Option<lint::LintBuffer>>,
 
     /// Set of `(DiagnosticId, Option<Span>, message)` tuples tracking
@@ -1213,7 +1215,6 @@ fn build_session_(
         sysroot,
         local_crate_source_file,
         working_dir,
-        lint_store: RwLock::new(lint::LintStore::new()),
         buffered_lints: Lock::new(Some(Default::default())),
         one_time_diagnostics: Default::default(),
         plugin_llvm_passes: OneThread::new(RefCell::new(Vec::new())),

src/librustc/traits/error_reporting.rs

@@ -406,7 +406,7 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
                 },
                 GenericParamDefKind::Lifetime => continue,
             };
-            let name = param.name.as_symbol();
+            let name = param.name;
             flags.push((name, Some(value)));
         }
 

src/librustc/traits/object_safety.rs

@@ -19,7 +19,7 @@ use crate::ty::subst::{Subst, InternalSubsts};
 use std::borrow::Cow;
 use std::iter::{self};
 use syntax::ast::{self};
-use syntax::symbol::InternedString;
+use syntax::symbol::Symbol;
 use syntax_pos::{Span, DUMMY_SP};
 
 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
@@ -560,7 +560,7 @@ impl<'tcx> TyCtxt<'tcx> {
         // are implemented
         let unsized_self_ty: Ty<'tcx> = self.mk_ty_param(
             ::std::u32::MAX,
-            InternedString::intern("RustaceansAreAwesome"),
+            Symbol::intern("RustaceansAreAwesome"),
         );
 
         // `Receiver[Self => U]`

src/librustc/traits/on_unimplemented.rs

@@ -250,7 +250,7 @@ impl<'tcx> OnUnimplementedFormatString {
                     Position::ArgumentNamed(s) if s == sym::from_desugaring => (),
                     // So is `{A}` if A is a type parameter
                     Position::ArgumentNamed(s) => match generics.params.iter().find(|param| {
-                        param.name.as_symbol() == s
+                        param.name == s
                     }) {
                         Some(_) => (),
                         None => {
@@ -289,7 +289,7 @@ impl<'tcx> OnUnimplementedFormatString {
                 },
                 GenericParamDefKind::Lifetime => return None
             };
-            let name = param.name.as_symbol();
+            let name = param.name;
             Some((name, value))
         }).collect::<FxHashMap<Symbol, String>>();
         let empty_string = String::new();

src/librustc/traits/structural_impls.rs

@@ -4,7 +4,7 @@ use crate::traits;
 use crate::traits::project::Normalized;
 use crate::ty::fold::{TypeFoldable, TypeFolder, TypeVisitor};
 use crate::ty::{self, Lift, Ty, TyCtxt};
-use syntax::symbol::InternedString;
+use syntax::symbol::Symbol;
 
 use std::fmt;
 use std::rc::Rc;
@@ -261,11 +261,11 @@ impl fmt::Display for traits::QuantifierKind {
 /// for debug output in tests anyway.
 struct BoundNamesCollector {
     // Just sort by name because `BoundRegion::BrNamed` does not have a `BoundVar` index anyway.
-    regions: BTreeSet<InternedString>,
+    regions: BTreeSet<Symbol>,
 
     // Sort by `BoundVar` index, so usually this should be equivalent to the order given
     // by the list of type parameters.
-    types: BTreeMap<u32, InternedString>,
+    types: BTreeMap<u32, Symbol>,
 
     binder_index: ty::DebruijnIndex,
 }
@@ -319,7 +319,7 @@ impl<'tcx> TypeVisitor<'tcx> for BoundNamesCollector {
                     match bound_ty.kind {
                         ty::BoundTyKind::Param(name) => name,
                         ty::BoundTyKind::Anon =>
-                            InternedString::intern(&format!("^{}", bound_ty.var.as_u32()),
+                            Symbol::intern(&format!("^{}", bound_ty.var.as_u32()),
                         ),
                     }
                 );
@@ -340,7 +340,7 @@ impl<'tcx> TypeVisitor<'tcx> for BoundNamesCollector {
                     }
 
                     ty::BoundRegion::BrAnon(var) => {
-                        self.regions.insert(InternedString::intern(&format!("'^{}", var)));
+                        self.regions.insert(Symbol::intern(&format!("'^{}", var)));
                     }
 
                     _ => (),

src/librustc/ty/context.rs

@@ -72,7 +72,7 @@ use syntax::ast;
 use syntax::attr;
 use syntax::source_map::MultiSpan;
 use syntax::feature_gate;
-use syntax::symbol::{Symbol, InternedString, kw, sym};
+use syntax::symbol::{Symbol, kw, sym};
 use syntax_pos::Span;
 
 pub struct AllArenas {
@@ -949,7 +949,7 @@ impl<'tcx> CommonTypes<'tcx> {
             f64: mk(Float(ast::FloatTy::F64)),
             self_param: mk(ty::Param(ty::ParamTy {
                 index: 0,
-                name: kw::SelfUpper.as_interned_str(),
+                name: kw::SelfUpper,
             })),
 
             trait_object_dummy_self: mk(Infer(ty::FreshTy(0))),
@@ -1031,6 +1031,8 @@ pub struct GlobalCtxt<'tcx> {
 
     pub sess: &'tcx Session,
 
+    pub lint_store: Lrc<lint::LintStore>,
+
     pub dep_graph: DepGraph,
 
     pub prof: SelfProfilerRef,
@@ -1192,6 +1194,7 @@ impl<'tcx> TyCtxt<'tcx> {
     /// reference to the context, to allow formatting values that need it.
     pub fn create_global_ctxt(
         s: &'tcx Session,
+        lint_store: Lrc<lint::LintStore>,
         cstore: &'tcx CrateStoreDyn,
         local_providers: ty::query::Providers<'tcx>,
         extern_providers: ty::query::Providers<'tcx>,
@@ -1255,6 +1258,7 @@ impl<'tcx> TyCtxt<'tcx> {
 
         GlobalCtxt {
             sess: s,
+            lint_store,
             cstore,
             arena: WorkerLocal::new(|_| Arena::default()),
             interners,
@@ -2552,7 +2556,7 @@ impl<'tcx> TyCtxt<'tcx> {
     }
 
     #[inline]
-    pub fn mk_ty_param(self, index: u32, name: InternedString) -> Ty<'tcx> {
+    pub fn mk_ty_param(self, index: u32, name: Symbol) -> Ty<'tcx> {
         self.mk_ty(Param(ParamTy { index, name: name }))
     }
 
@@ -2560,7 +2564,7 @@ impl<'tcx> TyCtxt<'tcx> {
     pub fn mk_const_param(
         self,
         index: u32,
-        name: InternedString,
+        name: Symbol,
         ty: Ty<'tcx>
     ) -> &'tcx Const<'tcx> {
         self.mk_const(ty::Const {

src/librustc/ty/mod.rs

@@ -46,7 +46,7 @@ use std::ops::Range;
 use syntax::ast::{self, Name, Ident, NodeId};
 use syntax::attr;
 use syntax_expand::hygiene::ExpnId;
-use syntax::symbol::{kw, sym, Symbol, InternedString};
+use syntax::symbol::{kw, sym, Symbol};
 use syntax_pos::Span;
 
 use smallvec;
@@ -849,7 +849,7 @@ impl ty::EarlyBoundRegion {
     /// Does this early bound region have a name? Early bound regions normally
     /// always have names except when using anonymous lifetimes (`'_`).
     pub fn has_name(&self) -> bool {
-        self.name != kw::UnderscoreLifetime.as_interned_str()
+        self.name != kw::UnderscoreLifetime
     }
 }
 
@@ -866,7 +866,7 @@ pub enum GenericParamDefKind {
 
 #[derive(Clone, RustcEncodable, RustcDecodable, HashStable)]
 pub struct GenericParamDef {
-    pub name: InternedString,
+    pub name: Symbol,
     pub def_id: DefId,
     pub index: u32,
 
@@ -3019,7 +3019,7 @@ impl<'tcx> TyCtxt<'tcx> {
                     }),
                 _ => def_key.disambiguated_data.data.get_opt_name().unwrap_or_else(|| {
                     bug!("item_name: no name for {:?}", self.def_path(id));
-                }).as_symbol(),
+                }),
             }
         }
     }
@@ -3429,11 +3429,11 @@ pub struct CrateInherentImpls {
     pub inherent_impls: DefIdMap<Vec<DefId>>,
 }
 
-#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, RustcEncodable, RustcDecodable)]
+#[derive(Clone, Copy, PartialEq, Eq, RustcEncodable, RustcDecodable)]
 pub struct SymbolName {
     // FIXME: we don't rely on interning or equality here - better have
     // this be a `&'tcx str`.
-    pub name: InternedString
+    pub name: Symbol
 }
 
 impl_stable_hash_for!(struct self::SymbolName {
@@ -3443,11 +3443,24 @@ impl_stable_hash_for!(struct self::SymbolName {
 impl SymbolName {
     pub fn new(name: &str) -> SymbolName {
         SymbolName {
-            name: InternedString::intern(name)
+            name: Symbol::intern(name)
         }
     }
 }
 
+impl PartialOrd for SymbolName {
+    fn partial_cmp(&self, other: &SymbolName) -> Option<Ordering> {
+        self.name.as_str().partial_cmp(&other.name.as_str())
+    }
+}
+
+/// Ordering must use the chars to ensure reproducible builds.
+impl Ord for SymbolName {
+    fn cmp(&self, other: &SymbolName) -> Ordering {
+        self.name.as_str().cmp(&other.name.as_str())
+    }
+}
+
 impl fmt::Display for SymbolName {
     fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
         fmt::Display::fmt(&self.name, fmt)

src/librustc/ty/print/obsolete.rs

@@ -218,9 +218,9 @@ impl DefPathBasedNames<'tcx> {
         // foo::bar::ItemName::
         for part in self.tcx.def_path(def_id).data {
             if self.omit_disambiguators {
-                write!(output, "{}::", part.data.as_interned_str()).unwrap();
+                write!(output, "{}::", part.data.as_symbol()).unwrap();
             } else {
-                write!(output, "{}[{}]::", part.data.as_interned_str(), part.disambiguator)
+                write!(output, "{}[{}]::", part.data.as_symbol(), part.disambiguator)
                     .unwrap();
             }
         }

src/librustc/ty/print/pretty.rs

@@ -14,7 +14,7 @@ use rustc_apfloat::Float;
 use rustc_target::spec::abi::Abi;
 use syntax::ast;
 use syntax::attr::{SignedInt, UnsignedInt};
-use syntax::symbol::{kw, InternedString};
+use syntax::symbol::{kw, Symbol};
 
 use std::cell::Cell;
 use std::fmt::{self, Write as _};
@@ -384,7 +384,7 @@ pub trait PrettyPrinter<'tcx>:
                 let reexport = self.tcx().item_children(visible_parent)
                     .iter()
                     .find(|child| child.res.def_id() == def_id)
-                    .map(|child| child.ident.as_interned_str());
+                    .map(|child| child.ident.name);
                 if let Some(reexport) = reexport {
                     *name = reexport;
                 }
@@ -392,7 +392,7 @@ pub trait PrettyPrinter<'tcx>:
             // Re-exported `extern crate` (#43189).
             DefPathData::CrateRoot => {
                 data = DefPathData::TypeNs(
-                    self.tcx().original_crate_name(def_id.krate).as_interned_str(),
+                    self.tcx().original_crate_name(def_id.krate),
                 );
             }
             _ => {}
@@ -992,7 +992,7 @@ pub struct FmtPrinterData<'a, 'tcx, F> {
     empty_path: bool,
     in_value: bool,
 
-    used_region_names: FxHashSet<InternedString>,
+    used_region_names: FxHashSet<Symbol>,
     region_index: usize,
     binder_depth: usize,
 
@@ -1222,7 +1222,7 @@ impl<F: fmt::Write> Printer<'tcx> for FmtPrinter<'_, 'tcx, F> {
 
         // FIXME(eddyb) `name` should never be empty, but it
         // currently is for `extern { ... }` "foreign modules".
-        let name = disambiguated_data.data.as_interned_str().as_str();
+        let name = disambiguated_data.data.as_symbol().as_str();
         if !name.is_empty() {
             if !self.empty_path {
                 write!(self, "::")?;
@@ -1332,16 +1332,16 @@ impl<F: fmt::Write> PrettyPrinter<'tcx> for FmtPrinter<'_, 'tcx, F> {
 
         match *region {
             ty::ReEarlyBound(ref data) => {
-                data.name.as_symbol() != kw::Invalid &&
-                data.name.as_symbol() != kw::UnderscoreLifetime
+                data.name != kw::Invalid &&
+                data.name != kw::UnderscoreLifetime
             }
 
             ty::ReLateBound(_, br) |
             ty::ReFree(ty::FreeRegion { bound_region: br, .. }) |
             ty::RePlaceholder(ty::Placeholder { name: br, .. }) => {
                 if let ty::BrNamed(_, name) = br {
-                    if name.as_symbol() != kw::Invalid &&
-                       name.as_symbol() != kw::UnderscoreLifetime {
+                    if name != kw::Invalid &&
+                       name != kw::UnderscoreLifetime {
                         return true;
                     }
                 }
@@ -1397,7 +1397,7 @@ impl<F: fmt::Write> FmtPrinter<'_, '_, F> {
         // `explain_region()` or `note_and_explain_region()`.
         match *region {
             ty::ReEarlyBound(ref data) => {
-                if data.name.as_symbol() != kw::Invalid {
+                if data.name != kw::Invalid {
                     p!(write("{}", data.name));
                     return Ok(self);
                 }
@@ -1406,8 +1406,8 @@ impl<F: fmt::Write> FmtPrinter<'_, '_, F> {
             ty::ReFree(ty::FreeRegion { bound_region: br, .. }) |
             ty::RePlaceholder(ty::Placeholder { name: br, .. }) => {
                 if let ty::BrNamed(_, name) = br {
-                    if name.as_symbol() != kw::Invalid &&
-                       name.as_symbol() != kw::UnderscoreLifetime {
+                    if name != kw::Invalid &&
+                       name != kw::UnderscoreLifetime {
                         p!(write("{}", name));
                         return Ok(self);
                     }
@@ -1474,11 +1474,11 @@ impl<F: fmt::Write> FmtPrinter<'_, 'tcx, F> {
     where
         T: Print<'tcx, Self, Output = Self, Error = fmt::Error> + TypeFoldable<'tcx>,
     {
-        fn name_by_region_index(index: usize) -> InternedString {
+        fn name_by_region_index(index: usize) -> Symbol {
             match index {
-                0 => InternedString::intern("'r"),
-                1 => InternedString::intern("'s"),
-                i => InternedString::intern(&format!("'t{}", i-2)),
+                0 => Symbol::intern("'r"),
+                1 => Symbol::intern("'s"),
+                i => Symbol::intern(&format!("'t{}", i-2)),
             }
         }
 
@@ -1541,7 +1541,7 @@ impl<F: fmt::Write> FmtPrinter<'_, 'tcx, F> {
         where T: TypeFoldable<'tcx>
     {
 
-        struct LateBoundRegionNameCollector<'a>(&'a mut FxHashSet<InternedString>);
+        struct LateBoundRegionNameCollector<'a>(&'a mut FxHashSet<Symbol>);
         impl<'tcx> ty::fold::TypeVisitor<'tcx> for LateBoundRegionNameCollector<'_> {
             fn visit_region(&mut self, r: ty::Region<'tcx>) -> bool {
                 match *r {

src/librustc/ty/query/keys.rs

@@ -9,7 +9,7 @@ use crate::ty::fast_reject::SimplifiedType;
 use crate::mir;
 
 use syntax_pos::{Span, DUMMY_SP};
-use syntax_pos::symbol::InternedString;
+use syntax_pos::symbol::Symbol;
 
 /// The `Key` trait controls what types can legally be used as the key
 /// for a query.
@@ -188,7 +188,7 @@ impl<'tcx> Key for traits::Environment<'tcx> {
     }
 }
 
-impl Key for InternedString {
+impl Key for Symbol {
     fn query_crate(&self) -> CrateNum {
         LOCAL_CRATE
     }

src/librustc/ty/query/mod.rs

@@ -55,7 +55,6 @@ use std::ops::Deref;
 use std::sync::Arc;
 use std::any::type_name;
 use syntax_pos::{Span, DUMMY_SP};
-use syntax_pos::symbol::InternedString;
 use syntax::attr;
 use syntax::ast;
 use syntax::feature_gate;

src/librustc/ty/query/values.rs

@@ -1,7 +1,7 @@
 use crate::ty::{self, Ty, TyCtxt, AdtSizedConstraint};
 use crate::ty::util::NeedsDrop;
 
-use syntax::symbol::InternedString;
+use syntax::symbol::Symbol;
 
 pub(super) trait Value<'tcx>: Sized {
     fn from_cycle_error(tcx: TyCtxt<'tcx>) -> Self;
@@ -22,7 +22,7 @@ impl<'tcx> Value<'tcx> for Ty<'tcx> {
 
 impl<'tcx> Value<'tcx> for ty::SymbolName {
     fn from_cycle_error(_: TyCtxt<'tcx>) -> Self {
-        ty::SymbolName { name: InternedString::intern("<error>") }
+        ty::SymbolName { name: Symbol::intern("<error>") }
     }
 }
 

src/librustc/ty/sty.rs

@@ -24,7 +24,7 @@ use std::marker::PhantomData;
 use std::ops::Range;
 use rustc_target::spec::abi;
 use syntax::ast::{self, Ident};
-use syntax::symbol::{kw, InternedString};
+use syntax::symbol::{kw, Symbol};
 
 use self::InferTy::*;
 use self::TyKind::*;
@@ -55,7 +55,7 @@ pub enum BoundRegion {
     ///
     /// The `DefId` is needed to distinguish free regions in
     /// the event of shadowing.
-    BrNamed(DefId, InternedString),
+    BrNamed(DefId, Symbol),
 
     /// Anonymous region for the implicit env pointer parameter
     /// to a closure
@@ -1121,16 +1121,16 @@ pub type CanonicalPolyFnSig<'tcx> = Canonical<'tcx, Binder<FnSig<'tcx>>>;
          Hash, RustcEncodable, RustcDecodable, HashStable)]
 pub struct ParamTy {
     pub index: u32,
-    pub name: InternedString,
+    pub name: Symbol,
 }
 
 impl<'tcx> ParamTy {
-    pub fn new(index: u32, name: InternedString) -> ParamTy {
+    pub fn new(index: u32, name: Symbol) -> ParamTy {
         ParamTy { index, name: name }
     }
 
     pub fn for_self() -> ParamTy {
-        ParamTy::new(0, kw::SelfUpper.as_interned_str())
+        ParamTy::new(0, kw::SelfUpper)
     }
 
     pub fn for_def(def: &ty::GenericParamDef) -> ParamTy {
@@ -1146,11 +1146,11 @@ impl<'tcx> ParamTy {
          Eq, PartialEq, Ord, PartialOrd, HashStable)]
 pub struct ParamConst {
     pub index: u32,
-    pub name: InternedString,
+    pub name: Symbol,
 }
 
 impl<'tcx> ParamConst {
-    pub fn new(index: u32, name: InternedString) -> ParamConst {
+    pub fn new(index: u32, name: Symbol) -> ParamConst {
         ParamConst { index, name }
     }
 
@@ -1323,7 +1323,7 @@ impl<'tcx> rustc_serialize::UseSpecializedDecodable for Region<'tcx> {}
 pub struct EarlyBoundRegion {
     pub def_id: DefId,
     pub index: u32,
-    pub name: InternedString,
+    pub name: Symbol,
 }
 
 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
@@ -1387,7 +1387,7 @@ pub struct BoundTy {
 #[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, RustcEncodable, RustcDecodable)]
 pub enum BoundTyKind {
     Anon,
-    Param(InternedString),
+    Param(Symbol),
 }
 
 impl_stable_hash_for!(struct BoundTy { var, kind });

src/librustc_codegen_llvm/base.rs

@@ -36,7 +36,7 @@ use rustc_codegen_ssa::back::write::submit_codegened_module_to_llvm;
 
 use std::ffi::CString;
 use std::time::Instant;
-use syntax_pos::symbol::InternedString;
+use syntax_pos::symbol::Symbol;
 use rustc::hir::CodegenFnAttrs;
 
 use crate::value::Value;
@@ -105,7 +105,7 @@ pub fn iter_globals(llmod: &'ll llvm::Module) -> ValueIter<'ll> {
 
 pub fn compile_codegen_unit(
     tcx: TyCtxt<'tcx>,
-    cgu_name: InternedString,
+    cgu_name: Symbol,
     tx_to_llvm_workers: &std::sync::mpsc::Sender<Box<dyn std::any::Any + Send>>,
 ) {
     let prof_timer = tcx.prof.generic_activity("codegen_module");
@@ -131,7 +131,7 @@ pub fn compile_codegen_unit(
 
     fn module_codegen(
         tcx: TyCtxt<'_>,
-        cgu_name: InternedString,
+        cgu_name: Symbol,
     ) -> ModuleCodegen<ModuleLlvm> {
         let cgu = tcx.codegen_unit(cgu_name);
         // Instantiate monomorphizations without filling out definitions yet...

src/librustc_codegen_llvm/consts.rs

@@ -221,7 +221,7 @@ impl CodegenCx<'ll, 'tcx> {
                  def_id);
 
         let ty = instance.ty(self.tcx);
-        let sym = self.tcx.symbol_name(instance).name.as_symbol();
+        let sym = self.tcx.symbol_name(instance).name;
 
         debug!("get_static: sym={} instance={:?}", sym, instance);
 

src/librustc_codegen_llvm/debuginfo/metadata.rs

@@ -46,7 +46,7 @@ use std::iter;
 use std::ptr;
 use std::path::{Path, PathBuf};
 use syntax::ast;
-use syntax::symbol::{Interner, InternedString};
+use syntax::symbol::{Interner, Symbol};
 use syntax_pos::{self, Span, FileName};
 
 impl PartialEq for llvm::Metadata {
@@ -2125,7 +2125,7 @@ fn compute_type_parameters(cx: &CodegenCx<'ll, 'tcx>, ty: Ty<'tcx>) -> Option<&'
 
     fn get_parameter_names(cx: &CodegenCx<'_, '_>,
                            generics: &ty::Generics)
-                           -> Vec<InternedString> {
+                           -> Vec<Symbol> {
         let mut names = generics.parent.map_or(vec![], |def_id| {
             get_parameter_names(cx, cx.tcx.generics_of(def_id))
         });

src/librustc_codegen_llvm/debuginfo/mod.rs

@@ -36,7 +36,7 @@ use std::ffi::{CStr, CString};
 
 use syntax_pos::{self, Span, Pos};
 use syntax::ast;
-use syntax::symbol::InternedString;
+use syntax::symbol::Symbol;
 use rustc::ty::layout::{self, LayoutOf, HasTyCtxt};
 use rustc_codegen_ssa::traits::*;
 
@@ -490,7 +490,7 @@ impl DebugInfoMethods<'tcx> for CodegenCx<'ll, 'tcx> {
 
         fn get_parameter_names(cx: &CodegenCx<'_, '_>,
                                generics: &ty::Generics)
-                               -> Vec<InternedString> {
+                               -> Vec<Symbol> {
             let mut names = generics.parent.map_or(vec![], |def_id| {
                 get_parameter_names(cx, cx.tcx.generics_of(def_id))
             });

src/librustc_codegen_llvm/debuginfo/namespace.rs

@@ -35,7 +35,7 @@ pub fn item_namespace(cx: &CodegenCx<'ll, '_>, def_id: DefId) -> &'ll DIScope {
 
     let namespace_name = match def_key.disambiguated_data.data {
         DefPathData::CrateRoot => cx.tcx.crate_name(def_id.krate).as_str(),
-        data => data.as_interned_str().as_str()
+        data => data.as_symbol().as_str()
     };
 
     let namespace_name = SmallCStr::new(&namespace_name);

src/librustc_codegen_llvm/lib.rs

@@ -50,7 +50,6 @@ use rustc_codegen_ssa::CompiledModule;
 use errors::{FatalError, Handler};
 use rustc::dep_graph::WorkProduct;
 use syntax_expand::allocator::AllocatorKind;
-use syntax_pos::symbol::InternedString;
 pub use llvm_util::target_features;
 use std::any::Any;
 use std::sync::Arc;
@@ -123,7 +122,7 @@ impl ExtraBackendMethods for LlvmCodegenBackend {
     }
     fn compile_codegen_unit(
         &self, tcx: TyCtxt<'_>,
-        cgu_name: InternedString,
+        cgu_name: Symbol,
         tx: &std::sync::mpsc::Sender<Box<dyn Any + Send>>,
     ) {
         base::compile_codegen_unit(tcx, cgu_name, tx);

src/librustc_codegen_ssa/base.rs

@@ -526,7 +526,7 @@ pub fn codegen_crate<B: ExtraBackendMethods>(
     // unnecessarily.
     if tcx.dep_graph.is_fully_enabled() {
         for cgu in &codegen_units {
-            tcx.codegen_unit(cgu.name().clone());
+            tcx.codegen_unit(cgu.name());
         }
     }
 
@@ -614,7 +614,7 @@ pub fn codegen_crate<B: ExtraBackendMethods>(
         match cgu_reuse {
             CguReuse::No => {
                 let start_time = Instant::now();
-                backend.compile_codegen_unit(tcx, *cgu.name(), &ongoing_codegen.coordinator_send);
+                backend.compile_codegen_unit(tcx, cgu.name(), &ongoing_codegen.coordinator_send);
                 total_codegen_time += start_time.elapsed();
                 false
             }

src/librustc_codegen_ssa/debuginfo/type_names.rs

@@ -221,7 +221,7 @@ pub fn push_debuginfo_type_name<'tcx>(
             output.push_str(&tcx.crate_name(def_id.krate).as_str());
             for path_element in tcx.def_path(def_id).data {
                 output.push_str("::");
-                output.push_str(&path_element.data.as_interned_str().as_str());
+                output.push_str(&path_element.data.as_symbol().as_str());
             }
         } else {
             output.push_str(&tcx.item_name(def_id).as_str());

src/librustc_codegen_ssa/traits/backend.rs

@@ -10,7 +10,7 @@ use rustc_codegen_utils::codegen_backend::CodegenBackend;
 use std::sync::Arc;
 use std::sync::mpsc;
 use syntax_expand::allocator::AllocatorKind;
-use syntax_pos::symbol::InternedString;
+use syntax_pos::symbol::Symbol;
 
 pub trait BackendTypes {
     type Value: CodegenObject;
@@ -50,7 +50,7 @@ pub trait ExtraBackendMethods: CodegenBackend + WriteBackendMethods + Sized + Se
     fn compile_codegen_unit(
         &self,
         tcx: TyCtxt<'_>,
-        cgu_name: InternedString,
+        cgu_name: Symbol,
         tx_to_llvm_workers: &mpsc::Sender<Box<dyn std::any::Any + Send>>,
     );
     // If find_features is true this won't access `sess.crate_types` by assuming

src/librustc_codegen_utils/symbol_names.rs

@@ -95,7 +95,7 @@ use rustc::ty::query::Providers;
 use rustc::ty::{self, TyCtxt, Instance};
 use rustc::mir::mono::{MonoItem, InstantiationMode};
 
-use syntax_pos::symbol::InternedString;
+use syntax_pos::symbol::Symbol;
 
 use log::debug;
 
@@ -112,7 +112,7 @@ pub fn provide(providers: &mut Providers<'_>) {
     };
 }
 
-fn symbol_name(tcx: TyCtxt<'tcx>, instance: Instance<'tcx>) -> InternedString {
+fn symbol_name(tcx: TyCtxt<'tcx>, instance: Instance<'tcx>) -> Symbol {
     let def_id = instance.def_id();
     let substs = instance.substs;
 
@@ -123,13 +123,11 @@ fn symbol_name(tcx: TyCtxt<'tcx>, instance: Instance<'tcx>) -> InternedString {
     if def_id.is_local() {
         if tcx.plugin_registrar_fn(LOCAL_CRATE) == Some(def_id) {
             let disambiguator = tcx.sess.local_crate_disambiguator();
-            return
-                InternedString::intern(&tcx.sess.generate_plugin_registrar_symbol(disambiguator));
+            return Symbol::intern(&tcx.sess.generate_plugin_registrar_symbol(disambiguator));
         }
         if tcx.proc_macro_decls_static(LOCAL_CRATE) == Some(def_id) {
             let disambiguator = tcx.sess.local_crate_disambiguator();
-            return
-                InternedString::intern(&tcx.sess.generate_proc_macro_decls_symbol(disambiguator));
+            return Symbol::intern(&tcx.sess.generate_proc_macro_decls_symbol(disambiguator));
         }
     }
 
@@ -146,23 +144,22 @@ fn symbol_name(tcx: TyCtxt<'tcx>, instance: Instance<'tcx>) -> InternedString {
     let attrs = tcx.codegen_fn_attrs(def_id);
     if is_foreign {
         if let Some(name) = attrs.link_name {
-            return name.as_interned_str();
+            return name;
         }
         // Don't mangle foreign items.
-        return tcx.item_name(def_id).as_interned_str();
+        return tcx.item_name(def_id);
     }
 
-    if let Some(name) = &attrs.export_name {
+    if let Some(name) = attrs.export_name {
         // Use provided name
-        return name.as_interned_str();
+        return name;
     }
 
     if attrs.flags.contains(CodegenFnAttrFlags::NO_MANGLE) {
         // Don't mangle
-        return tcx.item_name(def_id).as_interned_str();
+        return tcx.item_name(def_id);
     }
 
-
     let is_generic = substs.non_erasable_generics().next().is_some();
     let avoid_cross_crate_conflicts =
         // If this is an instance of a generic function, we also hash in
@@ -222,5 +219,5 @@ fn symbol_name(tcx: TyCtxt<'tcx>, instance: Instance<'tcx>) -> InternedString {
         SymbolManglingVersion::V0 => v0::mangle(tcx, instance, instantiating_crate),
     };
 
-    InternedString::intern(&mangled)
+    Symbol::intern(&mangled)
 }

src/librustc_codegen_utils/symbol_names/legacy.rs

@@ -335,7 +335,7 @@ impl Printer<'tcx> for SymbolPrinter<'tcx> {
             self.path.finalize_pending_component();
         }
 
-        self.write_str(&disambiguated_data.data.as_interned_str().as_str())?;
+        self.write_str(&disambiguated_data.data.as_symbol().as_str())?;
         Ok(self)
     }
     fn path_generic_args(

src/librustc_data_structures/graph/dominators/mod.rs

@@ -17,7 +17,7 @@ pub fn dominators<G: ControlFlowGraph>(graph: &G) -> Dominators<G::Node> {
     dominators_given_rpo(graph, &rpo)
 }
 
-pub fn dominators_given_rpo<G: ControlFlowGraph>(
+fn dominators_given_rpo<G: ControlFlowGraph>(
     graph: &G,
     rpo: &[G::Node],
 ) -> Dominators<G::Node> {
@@ -43,14 +43,12 @@ pub fn dominators_given_rpo<G: ControlFlowGraph>(
             let mut new_idom = None;
             for pred in graph.predecessors(node) {
                 if immediate_dominators[pred].is_some() {
-                    // (*)
                     // (*) dominators for `pred` have been calculated
-                    new_idom = intersect_opt(
-                        &post_order_rank,
-                        &immediate_dominators,
-                        new_idom,
-                        Some(pred),
-                    );
+                    new_idom = Some(if let Some(new_idom) = new_idom {
+                        intersect(&post_order_rank, &immediate_dominators, new_idom, pred)
+                    } else {
+                        pred
+                    });
                 }
             }
 
@@ -67,19 +65,6 @@ pub fn dominators_given_rpo<G: ControlFlowGraph>(
     }
 }
 
-fn intersect_opt<Node: Idx>(
-    post_order_rank: &IndexVec<Node, usize>,
-    immediate_dominators: &IndexVec<Node, Option<Node>>,
-    node1: Option<Node>,
-    node2: Option<Node>,
-) -> Option<Node> {
-    match (node1, node2) {
-        (None, None) => None,
-        (Some(n), None) | (None, Some(n)) => Some(n),
-        (Some(n1), Some(n2)) => Some(intersect(post_order_rank, immediate_dominators, n1, n2)),
-    }
-}
-
 fn intersect<Node: Idx>(
     post_order_rank: &IndexVec<Node, usize>,
     immediate_dominators: &IndexVec<Node, Option<Node>>,

src/librustc_driver/Cargo.toml

@@ -16,6 +16,7 @@ log = "0.4"
 env_logger = { version = "0.7", default-features = false }
 rustc = { path = "../librustc" }
 rustc_target = { path = "../librustc_target" }
+rustc_lint = { path = "../librustc_lint" }
 rustc_data_structures = { path = "../librustc_data_structures" }
 errors = { path = "../librustc_errors", package = "rustc_errors" }
 rustc_metadata = { path = "../librustc_metadata" }

src/librustc_driver/lib.rs

@@ -106,6 +106,8 @@ pub fn abort_on_err<T>(result: Result<T, ErrorReported>, sess: &Session) -> T {
 pub trait Callbacks {
     /// Called before creating the compiler instance
     fn config(&mut self, _config: &mut interface::Config) {}
+    /// Called early during compilation to allow other drivers to easily register lints.
+    fn extra_lints(&mut self, _ls: &mut lint::LintStore) {}
     /// Called after parsing. Return value instructs the compiler whether to
     /// continue the compilation afterwards (defaults to `Compilation::Continue`)
     fn after_parsing(&mut self, _compiler: &interface::Compiler) -> Compilation {
@@ -182,6 +184,7 @@ pub fn run_compiler(
             stderr: None,
             crate_name: None,
             lint_caps: Default::default(),
+            register_lints: None,
         };
         callbacks.config(&mut config);
         config
@@ -202,9 +205,13 @@ pub fn run_compiler(
                     interface::run_compiler(config, |compiler| {
                         let sopts = &compiler.session().opts;
                         if sopts.describe_lints {
+                            let lint_store = rustc_lint::new_lint_store(
+                                sopts.debugging_opts.no_interleave_lints,
+                                compiler.session().unstable_options(),
+                            );
                             describe_lints(
                                 compiler.session(),
-                                &*compiler.session().lint_store.borrow(),
+                                &lint_store,
                                 false
                             );
                             return;
@@ -255,6 +262,7 @@ pub fn run_compiler(
         stderr: None,
         crate_name: None,
         lint_caps: Default::default(),
+        register_lints: None,
     };
 
     callbacks.config(&mut config);
@@ -321,12 +329,14 @@ pub fn run_compiler(
             return sess.compile_status();
         }
 
-        compiler.register_plugins()?;
+        {
+            let (_, _, lint_store) = &*compiler.register_plugins()?.peek();
 
-        // Lint plugins are registered; now we can process command line flags.
-        if sess.opts.describe_lints {
-            describe_lints(&sess, &sess.lint_store.borrow(), true);
-            return sess.compile_status();
+            // Lint plugins are registered; now we can process command line flags.
+            if sess.opts.describe_lints {
+                describe_lints(&sess, &lint_store, true);
+                return sess.compile_status();
+            }
         }
 
         compiler.expansion()?;
@@ -835,8 +845,7 @@ Available lint options:
 
 ");
 
-    fn sort_lints(sess: &Session, lints: Vec<(&'static Lint, bool)>) -> Vec<&'static Lint> {
-        let mut lints: Vec<_> = lints.into_iter().map(|(x, _)| x).collect();
+    fn sort_lints(sess: &Session, mut lints: Vec<&'static Lint>) -> Vec<&'static Lint> {
         // The sort doesn't case-fold but it's doubtful we care.
         lints.sort_by_cached_key(|x: &&Lint| (x.default_level(sess), x.name));
         lints
@@ -852,7 +861,7 @@ Available lint options:
     let (plugin, builtin): (Vec<_>, _) = lint_store.get_lints()
                                                    .iter()
                                                    .cloned()
-                                                   .partition(|&(_, p)| p);
+                                                   .partition(|&lint| lint.is_plugin);
     let plugin = sort_lints(sess, plugin);
     let builtin = sort_lints(sess, builtin);
 

src/librustc_incremental/assert_module_sources.rs

@@ -27,7 +27,7 @@ use rustc::mir::mono::CodegenUnitNameBuilder;
 use rustc::ty::TyCtxt;
 use std::collections::BTreeSet;
 use syntax::ast;
-use syntax::symbol::{InternedString, Symbol, sym};
+use syntax::symbol::{Symbol, sym};
 use rustc::ich::{ATTR_PARTITION_REUSED, ATTR_PARTITION_CODEGENED,
                  ATTR_EXPECTED_CGU_REUSE};
 
@@ -45,8 +45,8 @@ pub fn assert_module_sources(tcx: TyCtxt<'_>) {
             .collect_and_partition_mono_items(LOCAL_CRATE)
             .1
             .iter()
-            .map(|cgu| *cgu.name())
-            .collect::<BTreeSet<InternedString>>();
+            .map(|cgu| cgu.name())
+            .collect::<BTreeSet<Symbol>>();
 
         let ams = AssertModuleSource {
             tcx,
@@ -61,7 +61,7 @@ pub fn assert_module_sources(tcx: TyCtxt<'_>) {
 
 struct AssertModuleSource<'tcx> {
     tcx: TyCtxt<'tcx>,
-    available_cgus: BTreeSet<InternedString>,
+    available_cgus: BTreeSet<Symbol>,
 }
 
 impl AssertModuleSource<'tcx> {

src/librustc_interface/interface.rs

@@ -39,6 +39,7 @@ pub struct Compiler {
     pub(crate) queries: Queries,
     pub(crate) cstore: Lrc<CStore>,
     pub(crate) crate_name: Option<String>,
+    pub(crate) register_lints: Option<Box<dyn Fn(&Session, &mut lint::LintStore) + Send + Sync>>,
 }
 
 impl Compiler {
@@ -137,6 +138,13 @@ pub struct Config {
 
     pub crate_name: Option<String>,
     pub lint_caps: FxHashMap<lint::LintId, lint::Level>,
+
+    /// This is a callback from the driver that is called when we're registering lints;
+    /// it is called during plugin registration when we have the LintStore in a non-shared state.
+    ///
+    /// Note that if you find a Some here you probably want to call that function in the new
+    /// function being registered.
+    pub register_lints: Option<Box<dyn Fn(&Session, &mut lint::LintStore) + Send + Sync>>,
 }
 
 pub fn run_compiler_in_existing_thread_pool<F, R>(config: Config, f: F) -> R
@@ -165,6 +173,7 @@ where
         output_file: config.output_file,
         queries: Default::default(),
         crate_name: config.crate_name,
+        register_lints: config.register_lints,
     };
 
     let _sess_abort_error = OnDrop(|| {

src/librustc_interface/passes.rs

@@ -117,6 +117,7 @@ declare_box_region_type!(
 /// Returns `None` if we're aborting after handling -W help.
 pub fn configure_and_expand(
     sess: Lrc<Session>,
+    lint_store: Lrc<lint::LintStore>,
     cstore: Lrc<CStore>,
     krate: ast::Crate,
     crate_name: &str,
@@ -134,6 +135,7 @@ pub fn configure_and_expand(
         let resolver_arenas = Resolver::arenas();
         let res = configure_and_expand_inner(
             sess,
+            &lint_store,
             &*cstore,
             krate,
             &crate_name,
@@ -225,9 +227,10 @@ pub struct PluginInfo {
 pub fn register_plugins<'a>(
     sess: &'a Session,
     cstore: &'a CStore,
+    register_lints: impl Fn(&Session, &mut lint::LintStore),
     mut krate: ast::Crate,
     crate_name: &str,
-) -> Result<(ast::Crate, PluginInfo)> {
+) -> Result<(ast::Crate, PluginInfo, Lrc<lint::LintStore>)> {
     krate = time(sess, "attributes injection", || {
         syntax_ext::cmdline_attrs::inject(
             krate, &sess.parse_sess, &sess.opts.debugging_opts.crate_attr
@@ -278,7 +281,14 @@ pub fn register_plugins<'a>(
         )
     });
 
-    let mut registry = Registry::new(sess, krate.span);
+    let mut lint_store = rustc_lint::new_lint_store(
+        sess.opts.debugging_opts.no_interleave_lints,
+        sess.unstable_options(),
+    );
+
+    (register_lints)(&sess, &mut lint_store);
+
+    let mut registry = Registry::new(sess, &mut lint_store, krate.span);
 
     time(sess, "plugin registration", || {
         for registrar in registrars {
@@ -289,34 +299,20 @@ pub fn register_plugins<'a>(
 
     let Registry {
         syntax_exts,
-        early_lint_passes,
-        late_lint_passes,
-        lint_groups,
         llvm_passes,
         attributes,
         ..
     } = registry;
 
-    let mut ls = sess.lint_store.borrow_mut();
-    for pass in early_lint_passes {
-        ls.register_early_pass(Some(sess), true, false, pass);
-    }
-    for pass in late_lint_passes {
-        ls.register_late_pass(Some(sess), true, false, false, pass);
-    }
-
-    for (name, (to, deprecated_name)) in lint_groups {
-        ls.register_group(Some(sess), true, name, deprecated_name, to);
-    }
-
     *sess.plugin_llvm_passes.borrow_mut() = llvm_passes;
     *sess.plugin_attributes.borrow_mut() = attributes;
 
-    Ok((krate, PluginInfo { syntax_exts }))
+    Ok((krate, PluginInfo { syntax_exts }, Lrc::new(lint_store)))
 }
 
 fn configure_and_expand_inner<'a>(
     sess: &'a Session,
+    lint_store: &'a lint::LintStore,
     cstore: &'a CStore,
     mut krate: ast::Crate,
     crate_name: &str,
@@ -327,6 +323,7 @@ fn configure_and_expand_inner<'a>(
     time(sess, "pre-AST-expansion lint checks", || {
         lint::check_ast_crate(
             sess,
+            lint_store,
             &krate,
             true,
             rustc_lint::BuiltinCombinedPreExpansionLintPass::new());
@@ -536,6 +533,7 @@ fn configure_and_expand_inner<'a>(
 
 pub fn lower_to_hir(
     sess: &Session,
+    lint_store: &lint::LintStore,
     cstore: &CStore,
     resolver: &mut Resolver<'_>,
     dep_graph: &DepGraph,
@@ -554,7 +552,13 @@ pub fn lower_to_hir(
     });
 
     time(sess, "early lint checks", || {
-        lint::check_ast_crate(sess, &krate, false, rustc_lint::BuiltinCombinedEarlyLintPass::new())
+        lint::check_ast_crate(
+            sess,
+            lint_store,
+            &krate,
+            false,
+            rustc_lint::BuiltinCombinedEarlyLintPass::new(),
+        )
     });
 
     // Discard hygiene data, which isn't required after lowering to HIR.
@@ -817,6 +821,7 @@ impl BoxedGlobalCtxt {
 
 pub fn create_global_ctxt(
     compiler: &Compiler,
+    lint_store: Lrc<lint::LintStore>,
     mut hir_forest: hir::map::Forest,
     defs: hir::map::Definitions,
     resolutions: Resolutions,
@@ -854,6 +859,7 @@ pub fn create_global_ctxt(
 
         let gcx = TyCtxt::create_global_ctxt(
             sess,
+            lint_store,
             cstore,
             local_providers,
             extern_providers,

src/librustc_interface/queries.rs

@@ -2,9 +2,13 @@ use crate::interface::{Compiler, Result};
 use crate::passes::{self, BoxedResolver, ExpansionResult, BoxedGlobalCtxt, PluginInfo};
 
 use rustc_incremental::DepGraphFuture;
+use rustc_data_structures::sync::Lrc;
 use rustc::session::config::{OutputFilenames, OutputType};
 use rustc::util::common::{time, ErrorReported};
 use rustc::hir;
+use rustc::lint;
+use rustc::session::Session;
+use rustc::lint::LintStore;
 use rustc::hir::def_id::LOCAL_CRATE;
 use rustc::ty::steal::Steal;
 use rustc::dep_graph::DepGraph;
@@ -74,8 +78,8 @@ pub(crate) struct Queries {
     dep_graph_future: Query<Option<DepGraphFuture>>,
     parse: Query<ast::Crate>,
     crate_name: Query<String>,
-    register_plugins: Query<(ast::Crate, PluginInfo)>,
-    expansion: Query<(ast::Crate, Steal<Rc<RefCell<BoxedResolver>>>)>,
+    register_plugins: Query<(ast::Crate, PluginInfo, Lrc<LintStore>)>,
+    expansion: Query<(ast::Crate, Steal<Rc<RefCell<BoxedResolver>>>, Lrc<LintStore>)>,
     dep_graph: Query<DepGraph>,
     lower_to_hir: Query<(Steal<hir::map::Forest>, ExpansionResult)>,
     prepare_outputs: Query<OutputFilenames>,
@@ -106,14 +110,19 @@ impl Compiler {
         })
     }
 
-    pub fn register_plugins(&self) -> Result<&Query<(ast::Crate, PluginInfo)>> {
+    pub fn register_plugins(&self) -> Result<&Query<(ast::Crate, PluginInfo, Lrc<LintStore>)>> {
         self.queries.register_plugins.compute(|| {
             let crate_name = self.crate_name()?.peek().clone();
             let krate = self.parse()?.take();
 
+            let empty: &(dyn Fn(&Session, &mut lint::LintStore) + Sync + Send) = &|_, _| {};
             let result = passes::register_plugins(
                 self.session(),
                 self.cstore(),
+                self.register_lints
+                    .as_ref()
+                    .map(|p| &**p)
+                    .unwrap_or_else(|| empty),
                 krate,
                 &crate_name,
             );
@@ -148,17 +157,20 @@ impl Compiler {
 
     pub fn expansion(
         &self
-    ) -> Result<&Query<(ast::Crate, Steal<Rc<RefCell<BoxedResolver>>>)>> {
+    ) -> Result<&Query<(ast::Crate, Steal<Rc<RefCell<BoxedResolver>>>, Lrc<LintStore>)>> {
         self.queries.expansion.compute(|| {
             let crate_name = self.crate_name()?.peek().clone();
-            let (krate, plugin_info) = self.register_plugins()?.take();
+            let (krate, plugin_info, lint_store) = self.register_plugins()?.take();
             passes::configure_and_expand(
                 self.sess.clone(),
+                lint_store.clone(),
                 self.cstore().clone(),
                 krate,
                 &crate_name,
                 plugin_info,
-            ).map(|(krate, resolver)| (krate, Steal::new(Rc::new(RefCell::new(resolver)))))
+            ).map(|(krate, resolver)| {
+                (krate, Steal::new(Rc::new(RefCell::new(resolver))), lint_store)
+            })
         })
     }
 
@@ -185,9 +197,11 @@ impl Compiler {
             let peeked = expansion_result.peek();
             let krate = &peeked.0;
             let resolver = peeked.1.steal();
+            let lint_store = &peeked.2;
             let hir = Steal::new(resolver.borrow_mut().access(|resolver| {
                 passes::lower_to_hir(
                     self.session(),
+                    lint_store,
                     self.cstore(),
                     resolver,
                     &*self.dep_graph()?.peek(),
@@ -212,11 +226,13 @@ impl Compiler {
         self.queries.global_ctxt.compute(|| {
             let crate_name = self.crate_name()?.peek().clone();
             let outputs = self.prepare_outputs()?.peek().clone();
+            let lint_store = self.expansion()?.peek().2.clone();
             let hir = self.lower_to_hir()?;
             let hir = hir.peek();
             let (ref hir_forest, ref expansion) = *hir;
             Ok(passes::create_global_ctxt(
                 self,
+                lint_store,
                 hir_forest.steal(),
                 expansion.defs.steal(),
                 expansion.resolutions.steal(),

src/librustc_interface/util.rs

@@ -13,7 +13,6 @@ use rustc_data_structures::fingerprint::Fingerprint;
 use rustc_data_structures::thin_vec::ThinVec;
 use rustc_data_structures::fx::{FxHashSet, FxHashMap};
 use rustc_errors::registry::Registry;
-use rustc_lint;
 use rustc_metadata::dynamic_lib::DynamicLibrary;
 use rustc_mir;
 use rustc_passes;
@@ -108,11 +107,6 @@ pub fn create_session(
 
     let codegen_backend = get_codegen_backend(&sess);
 
-    rustc_lint::register_builtins(&mut sess.lint_store.borrow_mut(), Some(&sess));
-    if sess.unstable_options() {
-        rustc_lint::register_internals(&mut sess.lint_store.borrow_mut(), Some(&sess));
-    }
-
     let mut cfg = config::build_configuration(&sess, config::to_crate_config(cfg));
     add_configuration(&mut cfg, &sess, &*codegen_backend);
     sess.parse_sess.config = cfg;

src/librustc_lint/builtin.rs

@@ -27,6 +27,7 @@ use rustc::hir::def::{Res, DefKind};
 use rustc::hir::def_id::{DefId, LOCAL_CRATE};
 use rustc::ty::{self, Ty, TyCtxt, layout::VariantIdx};
 use rustc::{lint, util};
+use rustc::lint::FutureIncompatibleInfo;
 use hir::Node;
 use util::nodemap::HirIdSet;
 use lint::{LateContext, LintContext, LintArray};
@@ -280,7 +281,7 @@ declare_lint! {
     pub MISSING_DOCS,
     Allow,
     "detects missing documentation for public members",
-    report_in_external_macro: true
+    report_in_external_macro
 }
 
 pub struct MissingDoc {
@@ -601,7 +602,11 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MissingDebugImplementations {
 declare_lint! {
     pub ANONYMOUS_PARAMETERS,
     Allow,
-    "detects anonymous parameters"
+    "detects anonymous parameters",
+    @future_incompatible = FutureIncompatibleInfo {
+        reference: "issue #41686 <https://github.com/rust-lang/rust/issues/41686>",
+        edition: Some(Edition::Edition2018),
+    };
 }
 
 declare_lint_pass!(
@@ -1344,7 +1349,7 @@ declare_lint! {
     UNNAMEABLE_TEST_ITEMS,
     Warn,
     "detects an item that cannot be named being marked as `#[test_case]`",
-    report_in_external_macro: true
+    report_in_external_macro
 }
 
 pub struct UnnameableTestItems {
@@ -1393,7 +1398,11 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnnameableTestItems {
 declare_lint! {
     pub KEYWORD_IDENTS,
     Allow,
-    "detects edition keywords being used as an identifier"
+    "detects edition keywords being used as an identifier",
+    @future_incompatible = FutureIncompatibleInfo {
+        reference: "issue #49716 <https://github.com/rust-lang/rust/issues/49716>",
+        edition: Some(Edition::Edition2018),
+    };
 }
 
 declare_lint_pass!(

src/librustc_lint/lib.rs

@@ -33,27 +33,21 @@ use rustc::lint;
 use rustc::lint::{EarlyContext, LateContext, LateLintPass, EarlyLintPass, LintPass, LintArray};
 use rustc::lint::builtin::{
     BARE_TRAIT_OBJECTS,
-    ABSOLUTE_PATHS_NOT_STARTING_WITH_CRATE,
     ELIDED_LIFETIMES_IN_PATHS,
     EXPLICIT_OUTLIVES_REQUIREMENTS,
     INTRA_DOC_LINK_RESOLUTION_FAILURE,
     MISSING_DOC_CODE_EXAMPLES,
     PRIVATE_DOC_TESTS,
-    parser::ILL_FORMED_ATTRIBUTE_INPUT,
 };
-use rustc::session;
 use rustc::hir;
 use rustc::hir::def_id::DefId;
 use rustc::ty::query::Providers;
 use rustc::ty::TyCtxt;
 
 use syntax::ast;
-use syntax::edition::Edition;
 use syntax_pos::Span;
 
-use session::Session;
 use lint::LintId;
-use lint::FutureIncompatibleInfo;
 
 use redundant_semicolon::*;
 use nonstandard_style::*;
@@ -192,59 +186,60 @@ late_lint_passes!(declare_combined_late_pass, [pub BuiltinCombinedLateLintPass])
 
 late_lint_mod_passes!(declare_combined_late_pass, [BuiltinCombinedModuleLateLintPass]);
 
+pub fn new_lint_store(no_interleave_lints: bool, internal_lints: bool) -> lint::LintStore {
+    let mut lint_store = lint::LintStore::new();
+
+    register_builtins(&mut lint_store, no_interleave_lints);
+    if internal_lints {
+        register_internals(&mut lint_store);
+    }
+
+    lint_store
+}
+
 /// Tell the `LintStore` about all the built-in lints (the ones
 /// defined in this crate and the ones defined in
 /// `rustc::lint::builtin`).
-pub fn register_builtins(store: &mut lint::LintStore, sess: Option<&Session>) {
+fn register_builtins(store: &mut lint::LintStore, no_interleave_lints: bool) {
     macro_rules! add_lint_group {
-        ($sess:ident, $name:expr, $($lint:ident),*) => (
-            store.register_group($sess, false, $name, None, vec![$(LintId::of($lint)),*]);
+        ($name:expr, $($lint:ident),*) => (
+            store.register_group(false, $name, None, vec![$(LintId::of($lint)),*]);
         )
     }
 
     macro_rules! register_pass {
-        ($method:ident, $constructor:expr, [$($args:expr),*]) => (
-            store.$method(sess, false, false, $($args,)* box $constructor);
+        ($method:ident, $ty:ident, $constructor:expr) => (
+            store.register_lints(&$ty::get_lints());
+            store.$method(|| box $constructor);
         )
     }
 
     macro_rules! register_passes {
-        ([$method:ident, $args:tt], [$($passes:ident: $constructor:expr,)*]) => (
+        ($method:ident, [$($passes:ident: $constructor:expr,)*]) => (
             $(
-                register_pass!($method, $constructor, $args);
+                register_pass!($method, $passes, $constructor);
             )*
         )
     }
 
-    if sess.map(|sess| sess.opts.debugging_opts.no_interleave_lints).unwrap_or(false) {
-        pre_expansion_lint_passes!(register_passes, [register_pre_expansion_pass, []]);
-        early_lint_passes!(register_passes, [register_early_pass, []]);
-        late_lint_passes!(register_passes, [register_late_pass, [false]]);
-        late_lint_mod_passes!(register_passes, [register_late_pass, [true]]);
+    if no_interleave_lints {
+        pre_expansion_lint_passes!(register_passes, register_pre_expansion_pass);
+        early_lint_passes!(register_passes, register_early_pass);
+        late_lint_passes!(register_passes, register_late_pass);
+        late_lint_mod_passes!(register_passes, register_late_mod_pass);
     } else {
-        store.register_pre_expansion_pass(
-            sess,
-            false,
-            true,
-            box BuiltinCombinedPreExpansionLintPass::new()
-        );
-        store.register_early_pass(sess, false, true, box BuiltinCombinedEarlyLintPass::new());
-        store.register_late_pass(
-            sess, false, true, true, box BuiltinCombinedModuleLateLintPass::new()
-        );
-        store.register_late_pass(
-            sess, false, true, false, box BuiltinCombinedLateLintPass::new()
-        );
+        store.register_lints(&BuiltinCombinedPreExpansionLintPass::get_lints());
+        store.register_lints(&BuiltinCombinedEarlyLintPass::get_lints());
+        store.register_lints(&BuiltinCombinedModuleLateLintPass::get_lints());
+        store.register_lints(&BuiltinCombinedLateLintPass::get_lints());
     }
 
-    add_lint_group!(sess,
-                    "nonstandard_style",
+    add_lint_group!("nonstandard_style",
                     NON_CAMEL_CASE_TYPES,
                     NON_SNAKE_CASE,
                     NON_UPPER_CASE_GLOBALS);
 
-    add_lint_group!(sess,
-                    "unused",
+    add_lint_group!("unused",
                     UNUSED_IMPORTS,
                     UNUSED_VARIABLES,
                     UNUSED_ASSIGNMENTS,
@@ -265,8 +260,7 @@ pub fn register_builtins(store: &mut lint::LintStore, sess: Option<&Session>) {
                     UNUSED_LABELS,
                     UNUSED_PARENS);
 
-    add_lint_group!(sess,
-                    "rust_2018_idioms",
+    add_lint_group!("rust_2018_idioms",
                     BARE_TRAIT_OBJECTS,
                     UNUSED_EXTERN_CRATES,
                     ELLIPSIS_INCLUSIVE_RANGE_PATTERNS,
@@ -282,165 +276,11 @@ pub fn register_builtins(store: &mut lint::LintStore, sess: Option<&Session>) {
                     // MACRO_USE_EXTERN_CRATE,
                     );
 
-    add_lint_group!(sess,
-                    "rustdoc",
+    add_lint_group!("rustdoc",
                     INTRA_DOC_LINK_RESOLUTION_FAILURE,
                     MISSING_DOC_CODE_EXAMPLES,
                     PRIVATE_DOC_TESTS);
 
-    // Guidelines for creating a future incompatibility lint:
-    //
-    // - Create a lint defaulting to warn as normal, with ideally the same error
-    //   message you would normally give
-    // - Add a suitable reference, typically an RFC or tracking issue. Go ahead
-    //   and include the full URL, sort items in ascending order of issue numbers.
-    // - Later, change lint to error
-    // - Eventually, remove lint
-    store.register_future_incompatible(sess, vec![
-        FutureIncompatibleInfo {
-            id: LintId::of(PRIVATE_IN_PUBLIC),
-            reference: "issue #34537 <https://github.com/rust-lang/rust/issues/34537>",
-            edition: None,
-        },
-        FutureIncompatibleInfo {
-            id: LintId::of(PUB_USE_OF_PRIVATE_EXTERN_CRATE),
-            reference: "issue #34537 <https://github.com/rust-lang/rust/issues/34537>",
-            edition: None,
-        },
-        FutureIncompatibleInfo {
-            id: LintId::of(PATTERNS_IN_FNS_WITHOUT_BODY),
-            reference: "issue #35203 <https://github.com/rust-lang/rust/issues/35203>",
-            edition: None,
-        },
-        FutureIncompatibleInfo {
-            id: LintId::of(DUPLICATE_MACRO_EXPORTS),
-            reference: "issue #35896 <https://github.com/rust-lang/rust/issues/35896>",
-            edition: Some(Edition::Edition2018),
-        },
-        FutureIncompatibleInfo {
-            id: LintId::of(KEYWORD_IDENTS),
-            reference: "issue #49716 <https://github.com/rust-lang/rust/issues/49716>",
-            edition: Some(Edition::Edition2018),
-        },
-        FutureIncompatibleInfo {
-            id: LintId::of(SAFE_EXTERN_STATICS),
-            reference: "issue #36247 <https://github.com/rust-lang/rust/issues/36247>",
-            edition: None,
-        },
-        FutureIncompatibleInfo {
-            id: LintId::of(INVALID_TYPE_PARAM_DEFAULT),
-            reference: "issue #36887 <https://github.com/rust-lang/rust/issues/36887>",
-            edition: None,
-        },
-        FutureIncompatibleInfo {
-            id: LintId::of(LEGACY_DIRECTORY_OWNERSHIP),
-            reference: "issue #37872 <https://github.com/rust-lang/rust/issues/37872>",
-            edition: None,
-        },
-        FutureIncompatibleInfo {
-            id: LintId::of(LEGACY_CONSTRUCTOR_VISIBILITY),
-            reference: "issue #39207 <https://github.com/rust-lang/rust/issues/39207>",
-            edition: None,
-        },
-        FutureIncompatibleInfo {
-            id: LintId::of(MISSING_FRAGMENT_SPECIFIER),
-            reference: "issue #40107 <https://github.com/rust-lang/rust/issues/40107>",
-            edition: None,
-        },
-        FutureIncompatibleInfo {
-            id: LintId::of(ILLEGAL_FLOATING_POINT_LITERAL_PATTERN),
-            reference: "issue #41620 <https://github.com/rust-lang/rust/issues/41620>",
-            edition: None,
-        },
-        FutureIncompatibleInfo {
-            id: LintId::of(ANONYMOUS_PARAMETERS),
-            reference: "issue #41686 <https://github.com/rust-lang/rust/issues/41686>",
-            edition: Some(Edition::Edition2018),
-        },
-        FutureIncompatibleInfo {
-            id: LintId::of(PARENTHESIZED_PARAMS_IN_TYPES_AND_MODULES),
-            reference: "issue #42238 <https://github.com/rust-lang/rust/issues/42238>",
-            edition: None,
-        },
-        FutureIncompatibleInfo {
-            id: LintId::of(LATE_BOUND_LIFETIME_ARGUMENTS),
-            reference: "issue #42868 <https://github.com/rust-lang/rust/issues/42868>",
-            edition: None,
-        },
-        FutureIncompatibleInfo {
-            id: LintId::of(SAFE_PACKED_BORROWS),
-            reference: "issue #46043 <https://github.com/rust-lang/rust/issues/46043>",
-            edition: None,
-        },
-        FutureIncompatibleInfo {
-            id: LintId::of(ORDER_DEPENDENT_TRAIT_OBJECTS),
-            reference: "issue #56484 <https://github.com/rust-lang/rust/issues/56484>",
-            edition: None,
-        },
-        FutureIncompatibleInfo {
-            id: LintId::of(TYVAR_BEHIND_RAW_POINTER),
-            reference: "issue #46906 <https://github.com/rust-lang/rust/issues/46906>",
-            edition: Some(Edition::Edition2018),
-        },
-        FutureIncompatibleInfo {
-            id: LintId::of(UNSTABLE_NAME_COLLISIONS),
-            reference: "issue #48919 <https://github.com/rust-lang/rust/issues/48919>",
-            edition: None,
-            // Note: this item represents future incompatibility of all unstable functions in the
-            //       standard library, and thus should never be removed or changed to an error.
-        },
-        FutureIncompatibleInfo {
-            id: LintId::of(ABSOLUTE_PATHS_NOT_STARTING_WITH_CRATE),
-            reference: "issue #53130 <https://github.com/rust-lang/rust/issues/53130>",
-            edition: Some(Edition::Edition2018),
-        },
-        FutureIncompatibleInfo {
-            id: LintId::of(WHERE_CLAUSES_OBJECT_SAFETY),
-            reference: "issue #51443 <https://github.com/rust-lang/rust/issues/51443>",
-            edition: None,
-        },
-        FutureIncompatibleInfo {
-            id: LintId::of(PROC_MACRO_DERIVE_RESOLUTION_FALLBACK),
-            reference: "issue #50504 <https://github.com/rust-lang/rust/issues/50504>",
-            edition: None,
-        },
-        FutureIncompatibleInfo {
-            id: LintId::of(MACRO_EXPANDED_MACRO_EXPORTS_ACCESSED_BY_ABSOLUTE_PATHS),
-            reference: "issue #52234 <https://github.com/rust-lang/rust/issues/52234>",
-            edition: None,
-        },
-        FutureIncompatibleInfo {
-            id: LintId::of(ILL_FORMED_ATTRIBUTE_INPUT),
-            reference: "issue #57571 <https://github.com/rust-lang/rust/issues/57571>",
-            edition: None,
-        },
-        FutureIncompatibleInfo {
-            id: LintId::of(AMBIGUOUS_ASSOCIATED_ITEMS),
-            reference: "issue #57644 <https://github.com/rust-lang/rust/issues/57644>",
-            edition: None,
-        },
-        FutureIncompatibleInfo {
-            id: LintId::of(NESTED_IMPL_TRAIT),
-            reference: "issue #59014 <https://github.com/rust-lang/rust/issues/59014>",
-            edition: None,
-        },
-        FutureIncompatibleInfo {
-            id: LintId::of(MUTABLE_BORROW_RESERVATION_CONFLICT),
-            reference: "issue #59159 <https://github.com/rust-lang/rust/issues/59159>",
-            edition: None,
-        },
-        FutureIncompatibleInfo {
-            id: LintId::of(INDIRECT_STRUCTURAL_MATCH),
-            reference: "issue #62411 <https://github.com/rust-lang/rust/issues/62411>",
-            edition: None,
-        },
-        FutureIncompatibleInfo {
-            id: LintId::of(SOFT_UNSTABLE),
-            reference: "issue #64266 <https://github.com/rust-lang/rust/issues/64266>",
-            edition: None,
-        },
-        ]);
-
     // Register renamed and removed lints.
     store.register_renamed("single_use_lifetime", "single_use_lifetimes");
     store.register_renamed("elided_lifetime_in_path", "elided_lifetimes_in_paths");
@@ -496,12 +336,14 @@ pub fn register_builtins(store: &mut lint::LintStore, sess: Option<&Session>) {
         "converted into hard error, see https://github.com/rust-lang/rust/issues/46205");
 }
 
-pub fn register_internals(store: &mut lint::LintStore, sess: Option<&Session>) {
-    store.register_early_pass(sess, false, false, box DefaultHashTypes::new());
-    store.register_early_pass(sess, false, false, box LintPassImpl);
-    store.register_late_pass(sess, false, false, false, box TyTyKind);
+fn register_internals(store: &mut lint::LintStore) {
+    store.register_lints(&DefaultHashTypes::get_lints());
+    store.register_early_pass(|| box DefaultHashTypes::new());
+    store.register_lints(&LintPassImpl::get_lints());
+    store.register_early_pass(|| box LintPassImpl);
+    store.register_lints(&TyTyKind::get_lints());
+    store.register_late_pass(|| box TyTyKind);
     store.register_group(
-        sess,
         false,
         "rustc::internal",
         None,

src/librustc_lint/unused.rs

@@ -25,7 +25,7 @@ declare_lint! {
     pub UNUSED_MUST_USE,
     Warn,
     "unused result of a type flagged as `#[must_use]`",
-    report_in_external_macro: true
+    report_in_external_macro
 }
 
 declare_lint! {

src/librustc_metadata/cstore_impl.rs

@@ -460,7 +460,7 @@ impl cstore::CStore {
 
         LoadedMacro::MacroDef(ast::Item {
             // FIXME: cross-crate hygiene
-            ident: ast::Ident::with_dummy_span(name.as_symbol()),
+            ident: ast::Ident::with_dummy_span(name),
             id: ast::DUMMY_NODE_ID,
             span: local_span,
             attrs: attrs.iter().cloned().collect(),

src/librustc_metadata/decoder.rs

@@ -35,7 +35,7 @@ use syntax::ast::{self, Ident};
 use syntax::source_map::{self, respan, Spanned};
 use syntax::symbol::{Symbol, sym};
 use syntax_expand::base::{MacroKind, SyntaxExtensionKind, SyntaxExtension};
-use syntax_pos::{self, Span, BytePos, Pos, DUMMY_SP, symbol::{InternedString}};
+use syntax_pos::{self, Span, BytePos, Pos, DUMMY_SP};
 use log::debug;
 use proc_macro::bridge::client::ProcMacro;
 use syntax_expand::proc_macro::{AttrProcMacro, ProcMacroDerive, BangProcMacro};
@@ -448,7 +448,7 @@ impl<'tcx> EntryKind<'tcx> {
             EntryKind::Mod(_) => DefKind::Mod,
             EntryKind::Variant(_) => DefKind::Variant,
             EntryKind::Trait(_) => DefKind::Trait,
-            EntryKind::TraitAlias(_) => DefKind::TraitAlias,
+            EntryKind::TraitAlias => DefKind::TraitAlias,
             EntryKind::Enum(..) => DefKind::Enum,
             EntryKind::MacroDef(_) => DefKind::Macro(MacroKind::Bang),
             EntryKind::ForeignType => DefKind::ForeignTy,
@@ -458,7 +458,7 @@ impl<'tcx> EntryKind<'tcx> {
             EntryKind::Impl(_) |
             EntryKind::Field |
             EntryKind::Generator(_) |
-            EntryKind::Closure(_) => return None,
+            EntryKind::Closure => return None,
         })
     }
 }
@@ -514,7 +514,6 @@ impl<'a, 'tcx> CrateMetadata {
                 .data
                 .get_opt_name()
                 .expect("no name in item_name")
-                .as_symbol()
         } else {
             Symbol::intern(self.raw_proc_macro(item_index).name())
         }
@@ -575,7 +574,7 @@ impl<'a, 'tcx> CrateMetadata {
                                   data.is_marker,
                                   self.def_path_table.def_path_hash(item_id))
             },
-            EntryKind::TraitAlias(_) => {
+            EntryKind::TraitAlias => {
                 ty::TraitDef::new(self.local_def_id(item_id),
                                   hir::Unsafety::Normal,
                                   false,
@@ -680,13 +679,7 @@ impl<'a, 'tcx> CrateMetadata {
         item_id: DefIndex,
         tcx: TyCtxt<'tcx>,
     ) -> ty::GenericPredicates<'tcx> {
-        let super_predicates = match self.kind(item_id) {
-            EntryKind::Trait(data) => data.decode(self).super_predicates,
-            EntryKind::TraitAlias(data) => data.decode(self).super_predicates,
-            _ => bug!("def-index does not refer to trait or trait alias"),
-        };
-
-        super_predicates.decode((self, tcx))
+        self.root.per_def.super_predicates.get(self, item_id).unwrap().decode((self, tcx))
     }
 
     crate fn get_generics(&self, item_id: DefIndex, sess: &Session) -> ty::Generics {
@@ -717,7 +710,7 @@ impl<'a, 'tcx> CrateMetadata {
         }
     }
 
-    fn get_impl_data(&self, id: DefIndex) -> ImplData<'tcx> {
+    fn get_impl_data(&self, id: DefIndex) -> ImplData {
         match self.kind(id) {
             EntryKind::Impl(data) => data.decode(self),
             _ => bug!(),
@@ -744,7 +737,7 @@ impl<'a, 'tcx> CrateMetadata {
     }
 
     crate fn get_impl_trait(&self, id: DefIndex, tcx: TyCtxt<'tcx>) -> Option<ty::TraitRef<'tcx>> {
-        self.get_impl_data(id).trait_ref.map(|tr| tr.decode((self, tcx)))
+        self.root.per_def.impl_trait_ref.get(self, id).map(|tr| tr.decode((self, tcx)))
     }
 
     /// Iterates over all the stability attributes in the given crate.
@@ -864,7 +857,7 @@ impl<'a, 'tcx> CrateMetadata {
                 let span = self.get_span(child_index, sess);
                 if let (Some(kind), Some(name)) =
                     (self.def_kind(child_index), def_key.disambiguated_data.data.get_opt_name()) {
-                    let ident = Ident::from_interned_str(name);
+                    let ident = Ident::with_dummy_span(name);
                     let vis = self.get_visibility(child_index);
                     let def_id = self.local_def_id(child_index);
                     let res = Res::Def(kind, def_id);
@@ -987,7 +980,7 @@ impl<'a, 'tcx> CrateMetadata {
         };
 
         ty::AssocItem {
-            ident: Ident::from_interned_str(name),
+            ident: Ident::with_dummy_span(name),
             kind,
             vis: self.get_visibility(id),
             defaultness: container.defaultness(),
@@ -1118,7 +1111,7 @@ impl<'a, 'tcx> CrateMetadata {
         def_key.parent.and_then(|parent_index| {
             match self.kind(parent_index) {
                 EntryKind::Trait(_) |
-                EntryKind::TraitAlias(_) => Some(self.local_def_id(parent_index)),
+                EntryKind::TraitAlias => Some(self.local_def_id(parent_index)),
                 _ => None,
             }
         })
@@ -1245,16 +1238,7 @@ impl<'a, 'tcx> CrateMetadata {
     }
 
     crate fn fn_sig(&self, id: DefIndex, tcx: TyCtxt<'tcx>) -> ty::PolyFnSig<'tcx> {
-        let sig = match self.kind(id) {
-            EntryKind::Fn(data) |
-            EntryKind::ForeignFn(data) => data.decode(self).sig,
-            EntryKind::Method(data) => data.decode(self).fn_data.sig,
-            EntryKind::Variant(data) |
-            EntryKind::Struct(data, _) => data.decode(self).ctor_sig.unwrap(),
-            EntryKind::Closure(data) => data.decode(self).sig,
-            _ => bug!(),
-        };
-        sig.decode((self, tcx))
+        self.root.per_def.fn_sig.get(self, id).unwrap().decode((self, tcx))
     }
 
     #[inline]
@@ -1262,7 +1246,7 @@ impl<'a, 'tcx> CrateMetadata {
         let mut key = self.def_path_table.def_key(index);
         if self.is_proc_macro(index) {
             let name = self.raw_proc_macro(index).name();
-            key.disambiguated_data.data = DefPathData::MacroNs(InternedString::intern(name));
+            key.disambiguated_data.data = DefPathData::MacroNs(Symbol::intern(name));
         }
         key
     }

src/librustc_metadata/encoder.rs

@@ -71,11 +71,14 @@ struct PerDefTables<'tcx> {
     deprecation: PerDefTable<Lazy<attr::Deprecation>>,
 
     ty: PerDefTable<Lazy<Ty<'tcx>>>,
+    fn_sig: PerDefTable<Lazy<ty::PolyFnSig<'tcx>>>,
+    impl_trait_ref: PerDefTable<Lazy<ty::TraitRef<'tcx>>>,
     inherent_impls: PerDefTable<Lazy<[DefIndex]>>,
     variances: PerDefTable<Lazy<[ty::Variance]>>,
     generics: PerDefTable<Lazy<ty::Generics>>,
     predicates: PerDefTable<Lazy<ty::GenericPredicates<'tcx>>>,
     predicates_defined_on: PerDefTable<Lazy<ty::GenericPredicates<'tcx>>>,
+    super_predicates: PerDefTable<Lazy<ty::GenericPredicates<'tcx>>>,
 
     mir: PerDefTable<Lazy<mir::Body<'tcx>>>,
     promoted_mir: PerDefTable<Lazy<IndexVec<mir::Promoted, mir::Body<'tcx>>>>,
@@ -508,11 +511,14 @@ impl<'tcx> EncodeContext<'tcx> {
             deprecation: self.per_def.deprecation.encode(&mut self.opaque),
 
             ty: self.per_def.ty.encode(&mut self.opaque),
+            fn_sig: self.per_def.fn_sig.encode(&mut self.opaque),
+            impl_trait_ref: self.per_def.impl_trait_ref.encode(&mut self.opaque),
             inherent_impls: self.per_def.inherent_impls.encode(&mut self.opaque),
             variances: self.per_def.variances.encode(&mut self.opaque),
             generics: self.per_def.generics.encode(&mut self.opaque),
             predicates: self.per_def.predicates.encode(&mut self.opaque),
             predicates_defined_on: self.per_def.predicates_defined_on.encode(&mut self.opaque),
+            super_predicates: self.per_def.super_predicates.encode(&mut self.opaque),
 
             mir: self.per_def.mir.encode(&mut self.opaque),
             promoted_mir: self.per_def.promoted_mir.encode(&mut self.opaque),
@@ -635,13 +641,7 @@ impl EncodeContext<'tcx> {
         let data = VariantData {
             ctor_kind: variant.ctor_kind,
             discr: variant.discr,
-            // FIXME(eddyb) deduplicate these with `encode_enum_variant_ctor`.
             ctor: variant.ctor_def_id.map(|did| did.index),
-            ctor_sig: if variant.ctor_kind == CtorKind::Fn {
-                variant.ctor_def_id.map(|ctor_def_id| self.lazy(&tcx.fn_sig(ctor_def_id)))
-            } else {
-                None
-            },
         };
 
         let enum_id = tcx.hir().as_local_hir_id(enum_did).unwrap();
@@ -660,6 +660,11 @@ impl EncodeContext<'tcx> {
         self.encode_deprecation(def_id);
         self.encode_item_type(def_id);
         if variant.ctor_kind == CtorKind::Fn {
+            // FIXME(eddyb) encode signature only in `encode_enum_variant_ctor`.
+            if let Some(ctor_def_id) = variant.ctor_def_id {
+                record!(self.per_def.fn_sig[def_id] <- tcx.fn_sig(ctor_def_id));
+            }
+            // FIXME(eddyb) is this ever used?
             self.encode_variances_of(def_id);
         }
         self.encode_generics(def_id);
@@ -679,15 +684,11 @@ impl EncodeContext<'tcx> {
         let def_id = variant.ctor_def_id.unwrap();
         debug!("EncodeContext::encode_enum_variant_ctor({:?})", def_id);
 
+        // FIXME(eddyb) encode only the `CtorKind` for constructors.
         let data = VariantData {
             ctor_kind: variant.ctor_kind,
             discr: variant.discr,
             ctor: Some(def_id.index),
-            ctor_sig: if variant.ctor_kind == CtorKind::Fn {
-                Some(self.lazy(tcx.fn_sig(def_id)))
-            } else {
-                None
-            }
         };
 
         // Variant constructors have the same visibility as the parent enums, unless marked as
@@ -706,6 +707,7 @@ impl EncodeContext<'tcx> {
         self.encode_deprecation(def_id);
         self.encode_item_type(def_id);
         if variant.ctor_kind == CtorKind::Fn {
+            record!(self.per_def.fn_sig[def_id] <- tcx.fn_sig(def_id));
             self.encode_variances_of(def_id);
         }
         self.encode_generics(def_id);
@@ -780,11 +782,6 @@ impl EncodeContext<'tcx> {
             ctor_kind: variant.ctor_kind,
             discr: variant.discr,
             ctor: Some(def_id.index),
-            ctor_sig: if variant.ctor_kind == CtorKind::Fn {
-                Some(self.lazy(tcx.fn_sig(def_id)))
-            } else {
-                None
-            }
         };
 
         let struct_id = tcx.hir().as_local_hir_id(adt_def_id).unwrap();
@@ -811,6 +808,7 @@ impl EncodeContext<'tcx> {
         self.encode_deprecation(def_id);
         self.encode_item_type(def_id);
         if variant.ctor_kind == CtorKind::Fn {
+            record!(self.per_def.fn_sig[def_id] <- tcx.fn_sig(def_id));
             self.encode_variances_of(def_id);
         }
         self.encode_generics(def_id);
@@ -835,6 +833,11 @@ impl EncodeContext<'tcx> {
             self.tcx.predicates_defined_on(def_id))
     }
 
+    fn encode_super_predicates(&mut self, def_id: DefId) {
+        debug!("EncodeContext::encode_super_predicates({:?})", def_id);
+        record!(self.per_def.super_predicates[def_id] <- self.tcx.super_predicates_of(def_id));
+    }
+
     fn encode_info_for_trait_item(&mut self, def_id: DefId) {
         debug!("EncodeContext::encode_info_for_trait_item({:?})", def_id);
         let tcx = self.tcx;
@@ -874,7 +877,6 @@ impl EncodeContext<'tcx> {
                         asyncness: m_sig.header.asyncness,
                         constness: hir::Constness::NotConst,
                         param_names,
-                        sig: self.lazy(tcx.fn_sig(def_id)),
                     }
                 } else {
                     bug!()
@@ -906,6 +908,7 @@ impl EncodeContext<'tcx> {
             ty::AssocKind::OpaqueTy => unreachable!(),
         }
         if trait_item.kind == ty::AssocKind::Method {
+            record!(self.per_def.fn_sig[def_id] <- tcx.fn_sig(def_id));
             self.encode_variances_of(def_id);
         }
         self.encode_generics(def_id);
@@ -952,7 +955,6 @@ impl EncodeContext<'tcx> {
                         asyncness: sig.header.asyncness,
                         constness: sig.header.constness,
                         param_names: self.encode_fn_param_names_for_body(body),
-                        sig: self.lazy(tcx.fn_sig(def_id)),
                     }
                 } else {
                     bug!()
@@ -973,6 +975,7 @@ impl EncodeContext<'tcx> {
         self.encode_deprecation(def_id);
         self.encode_item_type(def_id);
         if impl_item.kind == ty::AssocKind::Method {
+            record!(self.per_def.fn_sig[def_id] <- tcx.fn_sig(def_id));
             self.encode_variances_of(def_id);
         }
         self.encode_generics(def_id);
@@ -1081,7 +1084,6 @@ impl EncodeContext<'tcx> {
                     asyncness: header.asyncness,
                     constness: header.constness,
                     param_names: self.encode_fn_param_names_for_body(body),
-                    sig: self.lazy(tcx.fn_sig(def_id)),
                 };
 
                 EntryKind::Fn(self.lazy(data))
@@ -1109,7 +1111,6 @@ impl EncodeContext<'tcx> {
                     ctor_kind: variant.ctor_kind,
                     discr: variant.discr,
                     ctor,
-                    ctor_sig: None,
                 }), adt_def.repr)
             }
             hir::ItemKind::Union(..) => {
@@ -1120,7 +1121,6 @@ impl EncodeContext<'tcx> {
                     ctor_kind: variant.ctor_kind,
                     discr: variant.discr,
                     ctor: None,
-                    ctor_sig: None,
                 }), adt_def.repr)
             }
             hir::ItemKind::Impl(_, _, defaultness, ..) => {
@@ -1154,7 +1154,6 @@ impl EncodeContext<'tcx> {
                     defaultness,
                     parent_impl: parent,
                     coerce_unsized_info,
-                    trait_ref: trait_ref.map(|trait_ref| self.lazy(trait_ref)),
                 };
 
                 EntryKind::Impl(self.lazy(data))
@@ -1166,18 +1165,11 @@ impl EncodeContext<'tcx> {
                     paren_sugar: trait_def.paren_sugar,
                     has_auto_impl: self.tcx.trait_is_auto(def_id),
                     is_marker: trait_def.is_marker,
-                    super_predicates: self.lazy(tcx.super_predicates_of(def_id)),
                 };
 
                 EntryKind::Trait(self.lazy(data))
             }
-            hir::ItemKind::TraitAlias(..) => {
-                let data = TraitAliasData {
-                    super_predicates: self.lazy(tcx.super_predicates_of(def_id)),
-                };
-
-                EntryKind::TraitAlias(self.lazy(data))
-            }
+            hir::ItemKind::TraitAlias(..) => EntryKind::TraitAlias,
             hir::ItemKind::ExternCrate(_) |
             hir::ItemKind::Use(..) => bug!("cannot encode info for item {:?}", item),
         });
@@ -1232,6 +1224,14 @@ impl EncodeContext<'tcx> {
             hir::ItemKind::Impl(..) => self.encode_item_type(def_id),
             _ => {}
         }
+        if let hir::ItemKind::Fn(..) = item.kind {
+            record!(self.per_def.fn_sig[def_id] <- tcx.fn_sig(def_id));
+        }
+        if let hir::ItemKind::Impl(..) = item.kind {
+            if let Some(trait_ref) = self.tcx.impl_trait_ref(def_id) {
+                record!(self.per_def.impl_trait_ref[def_id] <- trait_ref);
+            }
+        }
         self.encode_inherent_implementations(def_id);
         match item.kind {
             hir::ItemKind::Enum(..) |
@@ -1269,6 +1269,13 @@ impl EncodeContext<'tcx> {
             }
             _ => {} // not *wrong* for other kinds of items, but not needed
         }
+        match item.kind {
+            hir::ItemKind::Trait(..) |
+            hir::ItemKind::TraitAlias(..) => {
+                self.encode_super_predicates(def_id);
+            }
+            _ => {}
+        }
 
         let mir = match item.kind {
             hir::ItemKind::Static(..) | hir::ItemKind::Const(..) => true,
@@ -1321,10 +1328,12 @@ impl EncodeContext<'tcx> {
     fn encode_info_for_closure(&mut self, def_id: DefId) {
         debug!("EncodeContext::encode_info_for_closure({:?})", def_id);
 
-        let tables = self.tcx.typeck_tables_of(def_id);
+        // NOTE(eddyb) `tcx.type_of(def_id)` isn't used because it's fully generic,
+        // including on the signature, which is inferred in `typeck_tables_of.
         let hir_id = self.tcx.hir().as_local_hir_id(def_id).unwrap();
+        let ty = self.tcx.typeck_tables_of(def_id).node_type(hir_id);
 
-        record!(self.per_def.kind[def_id] <- match tables.node_type(hir_id).kind {
+        record!(self.per_def.kind[def_id] <- match ty.kind {
             ty::Generator(def_id, ..) => {
                 let layout = self.tcx.generator_layout(def_id);
                 let data = GeneratorData {
@@ -1333,11 +1342,7 @@ impl EncodeContext<'tcx> {
                 EntryKind::Generator(self.lazy(data))
             }
 
-            ty::Closure(def_id, substs) => {
-                let sig = substs.as_closure().sig(def_id, self.tcx);
-                let data = ClosureData { sig: self.lazy(sig) };
-                EntryKind::Closure(self.lazy(data))
-            }
+            ty::Closure(..) => EntryKind::Closure,
 
             _ => bug!("closure that is neither generator nor closure"),
         });
@@ -1345,6 +1350,9 @@ impl EncodeContext<'tcx> {
         record!(self.per_def.span[def_id] <- self.tcx.def_span(def_id));
         record!(self.per_def.attributes[def_id] <- &self.tcx.get_attrs(def_id)[..]);
         self.encode_item_type(def_id);
+        if let ty::Closure(def_id, substs) = ty.kind {
+            record!(self.per_def.fn_sig[def_id] <- substs.as_closure().sig(def_id, self.tcx));
+        }
         self.encode_generics(def_id);
         self.encode_optimized_mir(def_id);
         self.encode_promoted_mir(def_id);
@@ -1553,7 +1561,6 @@ impl EncodeContext<'tcx> {
                     asyncness: hir::IsAsync::NotAsync,
                     constness: hir::Constness::NotConst,
                     param_names: self.encode_fn_param_names(names),
-                    sig: self.lazy(tcx.fn_sig(def_id)),
                 };
                 EntryKind::ForeignFn(self.lazy(data))
             }
@@ -1569,6 +1576,7 @@ impl EncodeContext<'tcx> {
         self.encode_deprecation(def_id);
         self.encode_item_type(def_id);
         if let hir::ForeignItemKind::Fn(..) = nitem.kind {
+            record!(self.per_def.fn_sig[def_id] <- tcx.fn_sig(def_id));
             self.encode_variances_of(def_id);
         }
         self.encode_generics(def_id);

src/librustc_metadata/schema.rs

@@ -238,11 +238,14 @@ crate struct LazyPerDefTables<'tcx> {
     pub deprecation: Lazy!(PerDefTable<Lazy<attr::Deprecation>>),
 
     pub ty: Lazy!(PerDefTable<Lazy!(Ty<'tcx>)>),
+    pub fn_sig: Lazy!(PerDefTable<Lazy!(ty::PolyFnSig<'tcx>)>),
+    pub impl_trait_ref: Lazy!(PerDefTable<Lazy!(ty::TraitRef<'tcx>)>),
     pub inherent_impls: Lazy!(PerDefTable<Lazy<[DefIndex]>>),
     pub variances: Lazy!(PerDefTable<Lazy<[ty::Variance]>>),
     pub generics: Lazy!(PerDefTable<Lazy<ty::Generics>>),
     pub predicates: Lazy!(PerDefTable<Lazy!(ty::GenericPredicates<'tcx>)>),
     pub predicates_defined_on: Lazy!(PerDefTable<Lazy!(ty::GenericPredicates<'tcx>)>),
+    pub super_predicates: Lazy!(PerDefTable<Lazy!(ty::GenericPredicates<'tcx>)>),
 
     pub mir: Lazy!(PerDefTable<Lazy!(mir::Body<'tcx>)>),
     pub promoted_mir: Lazy!(PerDefTable<Lazy!(IndexVec<mir::Promoted, mir::Body<'tcx>>)>),
@@ -264,22 +267,22 @@ crate enum EntryKind<'tcx> {
     OpaqueTy,
     Enum(ReprOptions),
     Field,
-    Variant(Lazy!(VariantData<'tcx>)),
-    Struct(Lazy!(VariantData<'tcx>), ReprOptions),
-    Union(Lazy!(VariantData<'tcx>), ReprOptions),
-    Fn(Lazy!(FnData<'tcx>)),
-    ForeignFn(Lazy!(FnData<'tcx>)),
+    Variant(Lazy<VariantData>),
+    Struct(Lazy<VariantData>, ReprOptions),
+    Union(Lazy<VariantData>, ReprOptions),
+    Fn(Lazy<FnData>),
+    ForeignFn(Lazy<FnData>),
     Mod(Lazy<ModData>),
     MacroDef(Lazy<MacroDef>),
-    Closure(Lazy!(ClosureData<'tcx>)),
+    Closure,
     Generator(Lazy!(GeneratorData<'tcx>)),
-    Trait(Lazy!(TraitData<'tcx>)),
-    Impl(Lazy!(ImplData<'tcx>)),
-    Method(Lazy!(MethodData<'tcx>)),
+    Trait(Lazy<TraitData>),
+    Impl(Lazy<ImplData>),
+    Method(Lazy<MethodData>),
     AssocType(AssocContainer),
     AssocOpaqueTy(AssocContainer),
     AssocConst(AssocContainer, ConstQualif, Lazy<RenderedConst>),
-    TraitAlias(Lazy!(TraitAliasData<'tcx>)),
+    TraitAlias,
 }
 
 /// Additional data for EntryKind::Const and EntryKind::AssocConst
@@ -305,47 +308,37 @@ crate struct MacroDef {
 }
 
 #[derive(RustcEncodable, RustcDecodable)]
-crate struct FnData<'tcx> {
+crate struct FnData {
     pub asyncness: hir::IsAsync,
     pub constness: hir::Constness,
     pub param_names: Lazy<[ast::Name]>,
-    pub sig: Lazy!(ty::PolyFnSig<'tcx>),
 }
 
 #[derive(RustcEncodable, RustcDecodable)]
-crate struct VariantData<'tcx> {
+crate struct VariantData {
     pub ctor_kind: CtorKind,
     pub discr: ty::VariantDiscr,
     /// If this is unit or tuple-variant/struct, then this is the index of the ctor id.
     pub ctor: Option<DefIndex>,
-    /// If this is a tuple struct or variant
-    /// ctor, this is its "function" signature.
-    pub ctor_sig: Option<Lazy!(ty::PolyFnSig<'tcx>)>,
 }
 
 #[derive(RustcEncodable, RustcDecodable)]
-crate struct TraitData<'tcx> {
+crate struct TraitData {
     pub unsafety: hir::Unsafety,
     pub paren_sugar: bool,
     pub has_auto_impl: bool,
     pub is_marker: bool,
-    pub super_predicates: Lazy!(ty::GenericPredicates<'tcx>),
 }
 
 #[derive(RustcEncodable, RustcDecodable)]
-crate struct TraitAliasData<'tcx> {
-    pub super_predicates: Lazy!(ty::GenericPredicates<'tcx>),
-}
-
-#[derive(RustcEncodable, RustcDecodable)]
-crate struct ImplData<'tcx> {
+crate struct ImplData {
     pub polarity: ty::ImplPolarity,
     pub defaultness: hir::Defaultness,
     pub parent_impl: Option<DefId>,
 
     /// This is `Some` only for impls of `CoerceUnsized`.
+    // FIXME(eddyb) perhaps compute this on the fly if cheap enough?
     pub coerce_unsized_info: Option<ty::adjustment::CoerceUnsizedInfo>,
-    pub trait_ref: Option<Lazy!(ty::TraitRef<'tcx>)>,
 }
 
 
@@ -388,17 +381,12 @@ impl AssocContainer {
 }
 
 #[derive(RustcEncodable, RustcDecodable)]
-crate struct MethodData<'tcx> {
-    pub fn_data: FnData<'tcx>,
+crate struct MethodData {
+    pub fn_data: FnData,
     pub container: AssocContainer,
     pub has_self: bool,
 }
 
-#[derive(RustcEncodable, RustcDecodable)]
-crate struct ClosureData<'tcx> {
-    pub sig: Lazy!(ty::PolyFnSig<'tcx>),
-}
-
 #[derive(RustcEncodable, RustcDecodable)]
 crate struct GeneratorData<'tcx> {
     pub layout: mir::GeneratorLayout<'tcx>,

src/librustc_mir/borrow_check/nll/region_infer/error_reporting/region_name.rs

@@ -18,14 +18,14 @@ use rustc::ty::print::RegionHighlightMode;
 use rustc_errors::DiagnosticBuilder;
 use syntax::symbol::kw;
 use rustc_data_structures::fx::FxHashMap;
-use syntax_pos::{Span, symbol::InternedString};
+use syntax_pos::{Span, symbol::Symbol};
 
 /// A name for a particular region used in emitting diagnostics. This name could be a generated
 /// name like `'1`, a name used by the user like `'a`, or a name like `'static`.
 #[derive(Debug, Clone)]
 crate struct RegionName {
     /// The name of the region (interned).
-    crate name: InternedString,
+    crate name: Symbol,
     /// Where the region comes from.
     crate source: RegionNameSource,
 }
@@ -109,7 +109,7 @@ impl RegionName {
     }
 
     #[allow(dead_code)]
-    crate fn name(&self) -> InternedString {
+    crate fn name(&self) -> Symbol {
         self.name
     }
 
@@ -273,7 +273,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
             }
 
             ty::ReStatic => Some(RegionName {
-                name: kw::StaticLifetime.as_interned_str(),
+                name: kw::StaticLifetime,
                 source: RegionNameSource::Static
             }),
 
@@ -360,7 +360,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         &self,
         tcx: TyCtxt<'tcx>,
         error_region: &RegionKind,
-        name: InternedString,
+        name: Symbol,
     ) -> Span {
         let scope = error_region.free_region_binding_scope(tcx);
         let node = tcx.hir().as_local_hir_id(scope).unwrap_or(hir::DUMMY_HIR_ID);
@@ -837,10 +837,10 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     }
 
     /// Creates a synthetic region named `'1`, incrementing the counter.
-    fn synthesize_region_name(&self, renctx: &mut RegionErrorNamingCtx) -> InternedString {
+    fn synthesize_region_name(&self, renctx: &mut RegionErrorNamingCtx) -> Symbol {
         let c = renctx.counter;
         renctx.counter += 1;
 
-        InternedString::intern(&format!("'{:?}", c))
+        Symbol::intern(&format!("'{:?}", c))
     }
 }

src/librustc_mir/borrow_check/nll/universal_regions.rs

@@ -790,7 +790,7 @@ fn for_each_late_bound_region_defined_on<'tcx>(
                 owner: fn_def_id.index,
                 local_id: *late_bound,
             };
-            let name = tcx.hir().name(hir_id).as_interned_str();
+            let name = tcx.hir().name(hir_id);
             let region_def_id = tcx.hir().local_def_id(hir_id);
             let liberated_region = tcx.mk_region(ty::ReFree(ty::FreeRegion {
                 scope: fn_def_id,

src/librustc_mir/hair/cx/expr.rs

@@ -908,7 +908,7 @@ fn convert_path_expr<'a, 'tcx>(
             let generics = cx.tcx.generics_of(item_def_id);
             let local_def_id = cx.tcx.hir().local_def_id(hir_id);
             let index = generics.param_def_id_to_index[&local_def_id];
-            let name = cx.tcx.hir().name(hir_id).as_interned_str();
+            let name = cx.tcx.hir().name(hir_id);
             let val = ConstValue::Param(ty::ParamConst::new(index, name));
             ExprKind::Literal {
                 literal: cx.tcx.mk_const(

src/librustc_mir/interpret/intrinsics/type_name.rs

@@ -148,7 +148,7 @@ impl<'tcx> Printer<'tcx> for AbsolutePathPrinter<'tcx> {
 
         self.path.push_str("::");
 
-        self.path.push_str(&disambiguated_data.data.as_interned_str().as_str());
+        self.path.push_str(&disambiguated_data.data.as_symbol().as_str());
         Ok(self)
     }
 

src/librustc_mir/interpret/memory.rs

@@ -7,7 +7,7 @@
 //! short-circuiting the empty case!
 
 use std::collections::VecDeque;
-use std::{ptr, iter};
+use std::ptr;
 use std::borrow::Cow;
 
 use rustc::ty::{self, Instance, ParamEnv, query::TyCtxtAt};
@@ -791,11 +791,12 @@ impl<'mir, 'tcx, M: Machine<'mir, 'tcx>> Memory<'mir, 'tcx, M> {
     pub fn write_bytes(
         &mut self,
         ptr: Scalar<M::PointerTag>,
-        src: impl IntoIterator<Item=u8, IntoIter: iter::ExactSizeIterator>,
+        src: impl IntoIterator<Item=u8>,
     ) -> InterpResult<'tcx>
     {
         let src = src.into_iter();
-        let size = Size::from_bytes(src.len() as u64);
+        let size = Size::from_bytes(src.size_hint().0 as u64);
+        // `write_bytes` checks that this lower bound matches the upper bound matches reality.
         let ptr = match self.check_ptr_access(ptr, size, Align::from_bytes(1).unwrap())? {
             Some(ptr) => ptr,
             None => return Ok(()), // zero-sized access

src/librustc_mir/monomorphize/partitioning.rs

@@ -96,7 +96,7 @@ use std::collections::hash_map::Entry;
 use std::cmp;
 use std::sync::Arc;
 
-use syntax::symbol::InternedString;
+use syntax::symbol::Symbol;
 use rustc::hir::CodegenFnAttrFlags;
 use rustc::hir::def::DefKind;
 use rustc::hir::def_id::{CrateNum, DefId, LOCAL_CRATE, CRATE_DEF_INDEX};
@@ -121,7 +121,7 @@ pub enum PartitioningStrategy {
 }
 
 // Anything we can't find a proper codegen unit for goes into this.
-fn fallback_cgu_name(name_builder: &mut CodegenUnitNameBuilder<'_>) -> InternedString {
+fn fallback_cgu_name(name_builder: &mut CodegenUnitNameBuilder<'_>) -> Symbol {
     name_builder.build_cgu_name(LOCAL_CRATE, &["fallback"], Some("cgu"))
 }
 
@@ -185,9 +185,7 @@ where
         internalization_candidates: _,
     } = post_inlining;
 
-    result.sort_by(|cgu1, cgu2| {
-        cgu1.name().cmp(cgu2.name())
-    });
+    result.sort_by_cached_key(|cgu| cgu.name().as_str());
 
     result
 }
@@ -203,7 +201,7 @@ struct PreInliningPartitioning<'tcx> {
 /// to keep track of that.
 #[derive(Clone, PartialEq, Eq, Debug)]
 enum MonoItemPlacement {
-    SingleCgu { cgu_name: InternedString },
+    SingleCgu { cgu_name: Symbol },
     MultipleCgus,
 }
 
@@ -251,8 +249,8 @@ where
             None => fallback_cgu_name(cgu_name_builder),
         };
 
-        let codegen_unit = codegen_units.entry(codegen_unit_name.clone())
-            .or_insert_with(|| CodegenUnit::new(codegen_unit_name.clone()));
+        let codegen_unit = codegen_units.entry(codegen_unit_name)
+            .or_insert_with(|| CodegenUnit::new(codegen_unit_name));
 
         let mut can_be_internalized = true;
         let (linkage, visibility) = mono_item_linkage_and_visibility(
@@ -273,8 +271,7 @@ where
     // crate with just types (for example), we could wind up with no CGU.
     if codegen_units.is_empty() {
         let codegen_unit_name = fallback_cgu_name(cgu_name_builder);
-        codegen_units.insert(codegen_unit_name.clone(),
-                             CodegenUnit::new(codegen_unit_name.clone()));
+        codegen_units.insert(codegen_unit_name, CodegenUnit::new(codegen_unit_name));
     }
 
     PreInliningPartitioning {
@@ -492,7 +489,7 @@ fn merge_codegen_units<'tcx>(
     // smallest into each other) we're sure to start off with a deterministic
     // order (sorted by name). This'll mean that if two cgus have the same size
     // the stable sort below will keep everything nice and deterministic.
-    codegen_units.sort_by_key(|cgu| *cgu.name());
+    codegen_units.sort_by_cached_key(|cgu| cgu.name().as_str());
 
     // Merge the two smallest codegen units until the target size is reached.
     while codegen_units.len() > target_cgu_count {
@@ -537,7 +534,7 @@ fn place_inlined_mono_items<'tcx>(initial_partitioning: PreInliningPartitioning<
             follow_inlining(*root, inlining_map, &mut reachable);
         }
 
-        let mut new_codegen_unit = CodegenUnit::new(old_codegen_unit.name().clone());
+        let mut new_codegen_unit = CodegenUnit::new(old_codegen_unit.name());
 
         // Add all monomorphizations that are not already there.
         for mono_item in reachable {
@@ -564,8 +561,8 @@ fn place_inlined_mono_items<'tcx>(initial_partitioning: PreInliningPartitioning<
                     Entry::Occupied(e) => {
                         let placement = e.into_mut();
                         debug_assert!(match *placement {
-                            MonoItemPlacement::SingleCgu { ref cgu_name } => {
-                                *cgu_name != *new_codegen_unit.name()
+                            MonoItemPlacement::SingleCgu { cgu_name } => {
+                                cgu_name != new_codegen_unit.name()
                             }
                             MonoItemPlacement::MultipleCgus => true,
                         });
@@ -573,7 +570,7 @@ fn place_inlined_mono_items<'tcx>(initial_partitioning: PreInliningPartitioning<
                     }
                     Entry::Vacant(e) => {
                         e.insert(MonoItemPlacement::SingleCgu {
-                            cgu_name: new_codegen_unit.name().clone()
+                            cgu_name: new_codegen_unit.name()
                         });
                     }
                 }
@@ -638,7 +635,7 @@ fn internalize_symbols<'tcx>(
     // accessed from outside its defining codegen unit.
     for cgu in &mut partitioning.codegen_units {
         let home_cgu = MonoItemPlacement::SingleCgu {
-            cgu_name: cgu.name().clone()
+            cgu_name: cgu.name()
         };
 
         for (accessee, linkage_and_visibility) in cgu.items_mut() {
@@ -717,7 +714,7 @@ fn characteristic_def_id_of_mono_item<'tcx>(
     }
 }
 
-type CguNameCache = FxHashMap<(DefId, bool), InternedString>;
+type CguNameCache = FxHashMap<(DefId, bool), Symbol>;
 
 fn compute_codegen_unit_name(
     tcx: TyCtxt<'_>,
@@ -725,7 +722,7 @@ fn compute_codegen_unit_name(
     def_id: DefId,
     volatile: bool,
     cache: &mut CguNameCache,
-) -> InternedString {
+) -> Symbol {
     // Find the innermost module that is not nested within a function.
     let mut current_def_id = def_id;
     let mut cgu_def_id = None;
@@ -762,7 +759,7 @@ fn compute_codegen_unit_name(
         let components = def_path
             .data
             .iter()
-            .map(|part| part.data.as_interned_str());
+            .map(|part| part.data.as_symbol());
 
         let volatile_suffix = if volatile {
             Some("volatile")
@@ -777,7 +774,7 @@ fn compute_codegen_unit_name(
 fn numbered_codegen_unit_name(
     name_builder: &mut CodegenUnitNameBuilder<'_>,
     index: usize,
-) -> InternedString {
+) -> Symbol {
     name_builder.build_cgu_name_no_mangle(LOCAL_CRATE, &["cgu"], Some(index))
 }
 
@@ -929,7 +926,7 @@ fn collect_and_partition_mono_items(
             for (&mono_item, &linkage) in cgu.items() {
                 item_to_cgus.entry(mono_item)
                             .or_default()
-                            .push((cgu.name().clone(), linkage));
+                            .push((cgu.name(), linkage));
             }
         }
 
@@ -991,7 +988,7 @@ pub fn provide(providers: &mut Providers<'_>) {
     providers.codegen_unit = |tcx, name| {
         let (_, all) = tcx.collect_and_partition_mono_items(LOCAL_CRATE);
         all.iter()
-            .find(|cgu| *cgu.name() == name)
+            .find(|cgu| cgu.name() == name)
             .cloned()
             .unwrap_or_else(|| panic!("failed to find cgu with name {:?}", name))
     };

src/librustc_mir/transform/check_unsafety.rs

@@ -12,7 +12,7 @@ use rustc::lint::builtin::{SAFE_EXTERN_STATICS, SAFE_PACKED_BORROWS, UNUSED_UNSA
 use rustc::mir::*;
 use rustc::mir::visit::{PlaceContext, Visitor, MutatingUseContext};
 
-use syntax::symbol::{InternedString, sym};
+use syntax::symbol::{Symbol, sym};
 
 use std::ops::Bound;
 
@@ -167,9 +167,8 @@ impl<'a, 'tcx> Visitor<'tcx> for UnsafetyChecker<'a, 'tcx> {
                     (CastTy::FnPtr, CastTy::Int(_)) => {
                         self.register_violations(&[UnsafetyViolation {
                             source_info: self.source_info,
-                            description: InternedString::intern("cast of pointer to int"),
-                            details: InternedString::intern(
-                                "casting pointers to integers in constants"),
+                            description: Symbol::intern("cast of pointer to int"),
+                            details: Symbol::intern("casting pointers to integers in constants"),
                             kind: UnsafetyViolationKind::General,
                         }], &[]);
                     },
@@ -185,8 +184,8 @@ impl<'a, 'tcx> Visitor<'tcx> for UnsafetyChecker<'a, 'tcx> {
                 if let ty::RawPtr(_) | ty::FnPtr(..) = lhs.ty(self.body, self.tcx).kind {
                     self.register_violations(&[UnsafetyViolation {
                         source_info: self.source_info,
-                        description: InternedString::intern("pointer operation"),
-                        details: InternedString::intern("operations on pointers in constants"),
+                        description: Symbol::intern("pointer operation"),
+                        details: Symbol::intern("operations on pointers in constants"),
                         kind: UnsafetyViolationKind::General,
                     }], &[]);
                 }
@@ -219,8 +218,8 @@ impl<'a, 'tcx> Visitor<'tcx> for UnsafetyChecker<'a, 'tcx> {
                         self.source_scope_local_data[source_info.scope].lint_root;
                     self.register_violations(&[UnsafetyViolation {
                         source_info,
-                        description: InternedString::intern("use of extern static"),
-                        details: InternedString::intern(
+                        description: Symbol::intern("use of extern static"),
+                        details: Symbol::intern(
                             "extern statics are not controlled by the Rust type system: \
                             invalid data, aliasing violations or data races will cause \
                             undefined behavior"),
@@ -240,8 +239,8 @@ impl<'a, 'tcx> Visitor<'tcx> for UnsafetyChecker<'a, 'tcx> {
                         self.source_scope_local_data[source_info.scope].lint_root;
                     self.register_violations(&[UnsafetyViolation {
                         source_info,
-                        description: InternedString::intern("borrow of packed field"),
-                        details: InternedString::intern(
+                        description: Symbol::intern("borrow of packed field"),
+                        details: Symbol::intern(
                             "fields of packed structs might be misaligned: dereferencing a \
                             misaligned pointer or even just creating a misaligned reference \
                             is undefined behavior"),
@@ -334,8 +333,8 @@ impl<'a, 'tcx> UnsafetyChecker<'a, 'tcx> {
         let source_info = self.source_info;
         self.register_violations(&[UnsafetyViolation {
             source_info,
-            description: InternedString::intern(description),
-            details: InternedString::intern(details),
+            description: Symbol::intern(description),
+            details: Symbol::intern(details),
             kind,
         }], &[]);
     }
@@ -438,8 +437,8 @@ impl<'a, 'tcx> UnsafetyChecker<'a, 'tcx> {
                                 let source_info = self.source_info;
                                 self.register_violations(&[UnsafetyViolation {
                                     source_info,
-                                    description: InternedString::intern(description),
-                                    details: InternedString::intern(details),
+                                    description: Symbol::intern(description),
+                                    details: Symbol::intern(details),
                                     kind: UnsafetyViolationKind::GeneralAndConstFn,
                                 }], &[]);
                             }

src/librustc_plugin/registry.rs

@@ -1,8 +1,7 @@
 //! Used by plugin crates to tell `rustc` about the plugins they provide.
 
-use rustc::lint::{EarlyLintPassObject, LateLintPassObject, LintId, Lint};
+use rustc::lint::LintStore;
 use rustc::session::Session;
-use rustc::util::nodemap::FxHashMap;
 
 use syntax_expand::base::{SyntaxExtension, SyntaxExtensionKind, NamedSyntaxExtension};
 use syntax_expand::base::MacroExpanderFn;
@@ -26,6 +25,9 @@ pub struct Registry<'a> {
     /// from the plugin registrar.
     pub sess: &'a Session,
 
+    /// The `LintStore` allows plugins to register new lints.
+    pub lint_store: &'a mut LintStore,
+
     #[doc(hidden)]
     pub args_hidden: Option<Vec<ast::NestedMetaItem>>,
 
@@ -35,15 +37,6 @@ pub struct Registry<'a> {
     #[doc(hidden)]
     pub syntax_exts: Vec<NamedSyntaxExtension>,
 
-    #[doc(hidden)]
-    pub early_lint_passes: Vec<EarlyLintPassObject>,
-
-    #[doc(hidden)]
-    pub late_lint_passes: Vec<LateLintPassObject>,
-
-    #[doc(hidden)]
-    pub lint_groups: FxHashMap<&'static str, (Vec<LintId>, Option<&'static str>)>,
-
     #[doc(hidden)]
     pub llvm_passes: Vec<String>,
 
@@ -53,15 +46,13 @@ pub struct Registry<'a> {
 
 impl<'a> Registry<'a> {
     #[doc(hidden)]
-    pub fn new(sess: &'a Session, krate_span: Span) -> Registry<'a> {
+    pub fn new(sess: &'a Session, lint_store: &'a mut LintStore, krate_span: Span) -> Registry<'a> {
         Registry {
             sess,
+            lint_store,
             args_hidden: None,
             krate_span,
             syntax_exts: vec![],
-            early_lint_passes: vec![],
-            late_lint_passes: vec![],
-            lint_groups: FxHashMap::default(),
             llvm_passes: vec![],
             attributes: vec![],
         }
@@ -99,27 +90,6 @@ impl<'a> Registry<'a> {
         self.register_syntax_extension(Symbol::intern(name), ext);
     }
 
-    /// Register a compiler lint pass.
-    pub fn register_early_lint_pass(&mut self, lint_pass: EarlyLintPassObject) {
-        self.early_lint_passes.push(lint_pass);
-    }
-
-    /// Register a compiler lint pass.
-    pub fn register_late_lint_pass(&mut self, lint_pass: LateLintPassObject) {
-        self.late_lint_passes.push(lint_pass);
-    }
-    /// Register a lint group.
-    pub fn register_lint_group(
-        &mut self,
-        name: &'static str,
-        deprecated_name: Option<&'static str>,
-        to: Vec<&'static Lint>
-    ) {
-        self.lint_groups.insert(name,
-                                (to.into_iter().map(|x| LintId::of(x)).collect(),
-                                 deprecated_name));
-    }
-
     /// Register an LLVM pass.
     ///
     /// Registration with LLVM itself is handled through static C++ objects with

src/librustc_resolve/build_reduced_graph.rs

@@ -110,14 +110,14 @@ impl<'a> Resolver<'a> {
         }
 
         let (name, parent) = if def_id.index == CRATE_DEF_INDEX {
-            (self.cstore.crate_name_untracked(def_id.krate).as_interned_str(), None)
+            (self.cstore.crate_name_untracked(def_id.krate), None)
         } else {
             let def_key = self.cstore.def_key(def_id);
             (def_key.disambiguated_data.data.get_opt_name().unwrap(),
              Some(self.get_module(DefId { index: def_key.parent.unwrap(), ..def_id })))
         };
 
-        let kind = ModuleKind::Def(DefKind::Mod, def_id, name.as_symbol());
+        let kind = ModuleKind::Def(DefKind::Mod, def_id, name);
         let module = self.arenas.alloc_module(ModuleData::new(
             parent, kind, def_id, ExpnId::root(), DUMMY_SP
         ));

src/librustc_resolve/error_codes.rs

@@ -1831,7 +1831,7 @@ An item usage is ambiguous.
 
 Erroneous code example:
 
-```compile_fail,E0659
+```compile_fail,edition2018,E0659
 pub mod moon {
     pub fn foo() {}
 }
@@ -1841,12 +1841,12 @@ pub mod earth {
 }
 
 mod collider {
-    pub use moon::*;
-    pub use earth::*;
+    pub use crate::moon::*;
+    pub use crate::earth::*;
 }
 
 fn main() {
-    collider::foo(); // ERROR: `foo` is ambiguous
+    crate::collider::foo(); // ERROR: `foo` is ambiguous
 }
 ```
 
@@ -1858,7 +1858,7 @@ functions collide.
 To solve this error, the best solution is generally to keep the path before the
 item when using it. Example:
 
-```
+```edition2018
 pub mod moon {
     pub fn foo() {}
 }
@@ -1868,13 +1868,13 @@ pub mod earth {
 }
 
 mod collider {
-    pub use moon;
-    pub use earth;
+    pub use crate::moon;
+    pub use crate::earth;
 }
 
 fn main() {
-    collider::moon::foo(); // ok!
-    collider::earth::foo(); // ok!
+    crate::collider::moon::foo(); // ok!
+    crate::collider::earth::foo(); // ok!
 }
 ```
 "##,

src/librustc_typeck/astconv.rs

@@ -131,7 +131,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
     {
         let tcx = self.tcx();
         let lifetime_name = |def_id| {
-            tcx.hir().name(tcx.hir().as_local_hir_id(def_id).unwrap()).as_interned_str()
+            tcx.hir().name(tcx.hir().as_local_hir_id(def_id).unwrap())
         };
 
         let r = match tcx.named_region(lifetime.hir_id) {
@@ -2022,7 +2022,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                 let item_def_id = tcx.hir().local_def_id(item_id);
                 let generics = tcx.generics_of(item_def_id);
                 let index = generics.param_def_id_to_index[&def_id];
-                tcx.mk_ty_param(index, tcx.hir().name(hir_id).as_interned_str())
+                tcx.mk_ty_param(index, tcx.hir().name(hir_id))
             }
             Res::SelfTy(Some(_), None) => {
                 // `Self` in trait or type alias.
@@ -2203,7 +2203,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
             let item_def_id = tcx.hir().local_def_id(item_id);
             let generics = tcx.generics_of(item_def_id);
             let index = generics.param_def_id_to_index[&tcx.hir().local_def_id(hir_id)];
-            let name = tcx.hir().name(hir_id).as_interned_str();
+            let name = tcx.hir().name(hir_id);
             const_.val = ConstValue::Param(ty::ParamConst::new(index, name));
         }
 

src/librustc_typeck/check/expr.rs

@@ -566,7 +566,17 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             // the `enclosing_loops` field and let's coerce the
             // type of `expr_opt` into what is expected.
             let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
-            let ctxt = enclosing_breakables.find_breakable(target_id);
+            let ctxt = match enclosing_breakables.opt_find_breakable(target_id) {
+                Some(ctxt) => ctxt,
+                None => { // Avoid ICE when `break` is inside a closure (#65383).
+                    self.tcx.sess.delay_span_bug(
+                        expr.span,
+                        "break was outside loop, but no error was emitted",
+                    );
+                    return tcx.types.err;
+                }
+            };
+
             if let Some(ref mut coerce) = ctxt.coerce {
                 if let Some(ref e) = expr_opt {
                     coerce.coerce(self, &cause, e, e_ty);
@@ -592,7 +602,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 }
             } else {
                 // If `ctxt.coerce` is `None`, we can just ignore
-                // the type of the expresison.  This is because
+                // the type of the expression.  This is because
                 // either this was a break *without* a value, in
                 // which case it is always a legal type (`()`), or
                 // else an error would have been flagged by the

src/librustc_typeck/check/intrinsic.rs

@@ -7,7 +7,7 @@ use rustc::ty::subst::Subst;
 use crate::require_same_types;
 
 use rustc_target::spec::abi::Abi;
-use syntax::symbol::InternedString;
+use syntax::symbol::Symbol;
 
 use rustc::hir;
 
@@ -80,7 +80,7 @@ pub fn intrinsic_operation_unsafety(intrinsic: &str) -> hir::Unsafety {
 /// Remember to add all intrinsics here, in librustc_codegen_llvm/intrinsic.rs,
 /// and in libcore/intrinsics.rs
 pub fn check_intrinsic_type(tcx: TyCtxt<'_>, it: &hir::ForeignItem) {
-    let param = |n| tcx.mk_ty_param(n, InternedString::intern(&format!("P{}", n)));
+    let param = |n| tcx.mk_ty_param(n, Symbol::intern(&format!("P{}", n)));
     let name = it.ident.as_str();
 
     let mk_va_list_ty = |mutbl| {
@@ -387,7 +387,7 @@ pub fn check_intrinsic_type(tcx: TyCtxt<'_>, it: &hir::ForeignItem) {
 /// Type-check `extern "platform-intrinsic" { ... }` functions.
 pub fn check_platform_intrinsic_type(tcx: TyCtxt<'_>, it: &hir::ForeignItem) {
     let param = |n| {
-        let name = InternedString::intern(&format!("P{}", n));
+        let name = Symbol::intern(&format!("P{}", n));
         tcx.mk_ty_param(n, name)
     };
 

src/librustc_typeck/check/mod.rs

@@ -536,10 +536,16 @@ pub struct EnclosingBreakables<'tcx> {
 
 impl<'tcx> EnclosingBreakables<'tcx> {
     fn find_breakable(&mut self, target_id: hir::HirId) -> &mut BreakableCtxt<'tcx> {
-        let ix = *self.by_id.get(&target_id).unwrap_or_else(|| {
+        self.opt_find_breakable(target_id).unwrap_or_else(|| {
             bug!("could not find enclosing breakable with id {}", target_id);
-        });
-        &mut self.stack[ix]
+        })
+    }
+
+    fn opt_find_breakable(&mut self, target_id: hir::HirId) -> Option<&mut BreakableCtxt<'tcx>> {
+        match self.by_id.get(&target_id) {
+            Some(ix) => Some(&mut self.stack[*ix]),
+            None => None,
+        }
     }
 }
 

src/librustc_typeck/collect.rs

@@ -36,7 +36,7 @@ use syntax::ast;
 use syntax::ast::{Ident, MetaItemKind};
 use syntax::attr::{InlineAttr, OptimizeAttr, list_contains_name, mark_used};
 use syntax::feature_gate;
-use syntax::symbol::{InternedString, kw, Symbol, sym};
+use syntax::symbol::{kw, Symbol, sym};
 use syntax_pos::{Span, DUMMY_SP};
 
 use rustc::hir::def::{CtorKind, Res, DefKind};
@@ -265,7 +265,7 @@ fn type_param_predicates(
     let param_owner_def_id = tcx.hir().local_def_id(param_owner);
     let generics = tcx.generics_of(param_owner_def_id);
     let index = generics.param_def_id_to_index[&def_id];
-    let ty = tcx.mk_ty_param(index, tcx.hir().ty_param_name(param_id).as_interned_str());
+    let ty = tcx.mk_ty_param(index, tcx.hir().ty_param_name(param_id));
 
     // Don't look for bounds where the type parameter isn't in scope.
     let parent = if item_def_id == param_owner_def_id {
@@ -961,7 +961,7 @@ fn generics_of(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::Generics {
 
                     opt_self = Some(ty::GenericParamDef {
                         index: 0,
-                        name: kw::SelfUpper.as_interned_str(),
+                        name: kw::SelfUpper,
                         def_id: tcx.hir().local_def_id(param_id),
                         pure_wrt_drop: false,
                         kind: ty::GenericParamDefKind::Type {
@@ -1006,7 +1006,7 @@ fn generics_of(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::Generics {
         early_lifetimes
             .enumerate()
             .map(|(i, param)| ty::GenericParamDef {
-                name: param.name.ident().as_interned_str(),
+                name: param.name.ident().name,
                 index: own_start + i as u32,
                 def_id: tcx.hir().local_def_id(param.hir_id),
                 pure_wrt_drop: param.pure_wrt_drop,
@@ -1060,7 +1060,7 @@ fn generics_of(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::Generics {
 
                 let param_def = ty::GenericParamDef {
                     index: type_start + i as u32,
-                    name: param.name.ident().as_interned_str(),
+                    name: param.name.ident().name,
                     def_id: tcx.hir().local_def_id(param.hir_id),
                     pure_wrt_drop: param.pure_wrt_drop,
                     kind,
@@ -1090,7 +1090,7 @@ fn generics_of(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::Generics {
                 .enumerate()
                 .map(|(i, &arg)| ty::GenericParamDef {
                     index: type_start + i as u32,
-                    name: InternedString::intern(arg),
+                    name: Symbol::intern(arg),
                     def_id,
                     pure_wrt_drop: false,
                     kind: ty::GenericParamDefKind::Type {
@@ -1105,7 +1105,7 @@ fn generics_of(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::Generics {
             params.extend(upvars.iter().zip((dummy_args.len() as u32)..).map(|(_, i)| {
                 ty::GenericParamDef {
                     index: type_start + i,
-                    name: InternedString::intern("<upvar>"),
+                    name: Symbol::intern("<upvar>"),
                     def_id,
                     pure_wrt_drop: false,
                     kind: ty::GenericParamDefKind::Type {
@@ -2198,7 +2198,7 @@ fn explicit_predicates_of(
         let region = tcx.mk_region(ty::ReEarlyBound(ty::EarlyBoundRegion {
             def_id: tcx.hir().local_def_id(param.hir_id),
             index,
-            name: param.name.ident().as_interned_str(),
+            name: param.name.ident().name,
         }));
         index += 1;
 
@@ -2221,7 +2221,7 @@ fn explicit_predicates_of(
     // type parameter (e.g., `<T: Foo>`).
     for param in &ast_generics.params {
         if let GenericParamKind::Type { .. } = param.kind {
-            let name = param.name.ident().as_interned_str();
+            let name = param.name.ident().name;
             let param_ty = ty::ParamTy::new(index, name).to_ty(tcx);
             index += 1;
 

src/librustdoc/clean/mod.rs

@@ -31,7 +31,6 @@ use syntax::attr;
 use syntax_expand::base::MacroKind;
 use syntax::source_map::DUMMY_SP;
 use syntax::symbol::{Symbol, kw, sym};
-use syntax::symbol::InternedString;
 use syntax_pos::{self, Pos, FileName};
 
 use std::collections::hash_map::Entry;
@@ -1682,7 +1681,7 @@ impl<'a, 'tcx> Clean<Generics> for (&'a ty::Generics, ty::GenericPredicates<'tcx
             .filter_map(|param| match param.kind {
                 ty::GenericParamDefKind::Lifetime => None,
                 ty::GenericParamDefKind::Type { synthetic, .. } => {
-                    if param.name.as_symbol() == kw::SelfUpper {
+                    if param.name == kw::SelfUpper {
                         assert_eq!(param.index, 0);
                         return None;
                     }
@@ -3701,13 +3700,6 @@ impl Clean<String> for ast::Name {
     }
 }
 
-impl Clean<String> for InternedString {
-    #[inline]
-    fn clean(&self, _: &DocContext<'_>) -> String {
-        self.to_string()
-    }
-}
-
 #[derive(Clone, Debug)]
 pub struct Typedef {
     pub type_: Type,

src/librustdoc/core.rs

@@ -5,7 +5,7 @@ use rustc::hir::HirId;
 use rustc::middle::cstore::CrateStore;
 use rustc::middle::privacy::AccessLevels;
 use rustc::ty::{Ty, TyCtxt};
-use rustc::lint::{self, LintPass};
+use rustc::lint;
 use rustc::session::config::ErrorOutputType;
 use rustc::session::DiagnosticOutput;
 use rustc::util::nodemap::{FxHashMap, FxHashSet};
@@ -273,10 +273,9 @@ pub fn run_core(options: RustdocOptions) -> (clean::Crate, RenderInfo, RenderOpt
     whitelisted_lints.extend(lint_opts.iter().map(|(lint, _)| lint).cloned());
 
     let lints = || {
-        lint::builtin::HardwiredLints
-            .get_lints()
+        lint::builtin::HardwiredLints::get_lints()
             .into_iter()
-            .chain(rustc_lint::SoftLints.get_lints().into_iter())
+            .chain(rustc_lint::SoftLints::get_lints().into_iter())
     };
 
     let lint_opts = lints().filter_map(|lint| {
@@ -339,6 +338,7 @@ pub fn run_core(options: RustdocOptions) -> (clean::Crate, RenderInfo, RenderOpt
         stderr: None,
         crate_name,
         lint_caps,
+        register_lints: None,
     };
 
     interface::run_compiler_in_existing_thread_pool(config, |compiler| {

src/librustdoc/test.rs

@@ -77,6 +77,7 @@ pub fn run(options: Options) -> i32 {
         stderr: None,
         crate_name: options.crate_name.clone(),
         lint_caps: Default::default(),
+        register_lints: None,
     };
 
     let mut test_args = options.test_args.clone();

src/libstd/lib.rs

@@ -276,6 +276,7 @@
 #![feature(linkage)]
 #![feature(log_syntax)]
 #![feature(manually_drop_take)]
+#![feature(matches_macro)]
 #![feature(maybe_uninit_ref)]
 #![feature(maybe_uninit_slice)]
 #![feature(needs_panic_runtime)]
@@ -527,6 +528,7 @@ pub use core::{
     writeln,
     // Unstable
     todo,
+    matches,
 };
 
 // Re-export built-in macros defined through libcore.

src/libstd/panicking.rs

@@ -217,7 +217,7 @@ pub fn update_panic_count(amt: isize) -> usize {
     PANIC_COUNT.with(|c| {
         let next = (c.get() as isize + amt) as usize;
         c.set(next);
-        return next
+        next
     })
 }
 

src/libstd/sys/unix/rand.rs

@@ -8,7 +8,7 @@ pub fn hashmap_random_keys() -> (u64, u64) {
                                              mem::size_of_val(&v));
         imp::fill_bytes(view);
     }
-    return v
+    v
 }
 
 #[cfg(all(unix,

src/libstd/sys/windows/handle.rs

@@ -46,7 +46,7 @@ impl Handle {
     pub fn into_raw(self) -> c::HANDLE {
         let ret = self.raw();
         mem::forget(self);
-        return ret;
+        ret
     }
 }
 

src/libstd/sys/windows/mutex.rs

@@ -144,7 +144,7 @@ fn kind() -> Kind {
         Some(..) => Kind::SRWLock,
     };
     KIND.store(ret as usize, Ordering::SeqCst);
-    return ret;
+    ret
 }
 
 pub struct ReentrantMutex { inner: UnsafeCell<MaybeUninit<c::CRITICAL_SECTION>> }

src/libstd/sys/windows/process.rs

@@ -257,7 +257,7 @@ impl Stdio {
                         let ret = io.duplicate(0, true,
                                                c::DUPLICATE_SAME_ACCESS);
                         io.into_raw();
-                        return ret
+                        ret
                     }
                     Err(..) => Ok(Handle::new(c::INVALID_HANDLE_VALUE)),
                 }
@@ -472,9 +472,8 @@ fn make_command_line(prog: &OsStr, args: &[OsString]) -> io::Result<Vec<u16>> {
             cmd.push('"' as u16);
         }
 
-        let mut iter = arg.encode_wide();
         let mut backslashes: usize = 0;
-        while let Some(x) = iter.next() {
+        for x in arg.encode_wide() {
             if x == '\\' as u16 {
                 backslashes += 1;
             } else {

src/libstd/sys/windows/rand.rs

@@ -13,7 +13,7 @@ pub fn hashmap_random_keys() -> (u64, u64) {
         panic!("couldn't generate random bytes: {}",
                io::Error::last_os_error());
     }
-    return v
+    v
 }
 
 #[cfg(target_vendor = "uwp")]

src/libstd/sys/windows/thread_local.rs

@@ -52,7 +52,7 @@ pub unsafe fn create(dtor: Option<Dtor>) -> Key {
     if let Some(f) = dtor {
         register_dtor(key, f);
     }
-    return key;
+    key
 }
 
 #[inline]

src/libstd/sys/windows/time.rs

@@ -80,7 +80,7 @@ impl SystemTime {
         unsafe {
             let mut t: SystemTime = mem::zeroed();
             c::GetSystemTimeAsFileTime(&mut t.t);
-            return t
+            t
         }
     }
 
@@ -228,7 +228,7 @@ mod perf_counter {
                 FREQUENCY = frequency;
                 STATE.store(2, SeqCst);
             }
-            return frequency;
+            frequency
         }
     }
 

src/libstd/thread/local.rs

@@ -509,9 +509,8 @@ pub mod os {
         pub unsafe fn get(&'static self, init: fn() -> T) -> Option<&'static T> {
             let ptr = self.os.get() as *mut Value<T>;
             if ptr as usize > 1 {
-                match (*ptr).inner.get() {
-                    Some(ref value) => return Some(value),
-                    None => {},
+                if let Some(ref value) = (*ptr).inner.get() {
+                    return Some(value);
                 }
             }
             self.try_initialize(init)