From f1b4c2a0e64ccb5c1b4b2b2391ac91f40d143302 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jana=20D=C3=B6nszelmann?= <jana@donsz.nl>
Date: Sat, 7 Feb 2026 14:42:17 +0100
Subject: [PATCH] Port rustc_insignificant_dtor to the new attribute parser

---
 .../src/attributes/rustc_internal.rs                | 13 +++++++++++++
 compiler/rustc_attr_parsing/src/context.rs          |  1 +
 compiler/rustc_hir/src/attrs/data_structures.rs     |  3 +++
 compiler/rustc_hir/src/attrs/encode_cross_crate.rs  |  1 +
 compiler/rustc_passes/src/check_attr.rs             |  2 +-
 compiler/rustc_ty_utils/src/needs_drop.rs           |  6 +++---
 6 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/compiler/rustc_attr_parsing/src/attributes/rustc_internal.rs b/compiler/rustc_attr_parsing/src/attributes/rustc_internal.rs
index a8a0ee3e5e22..4740cc107353 100644
--- a/compiler/rustc_attr_parsing/src/attributes/rustc_internal.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/rustc_internal.rs
@@ -739,6 +739,19 @@ impl<S: Stage> CombineAttributeParser<S> for RustcThenThisWouldNeedParser {
     }
 }
 
+pub(crate) struct RustcInsignificantDtorParser;
+
+impl<S: Stage> NoArgsAttributeParser<S> for RustcInsignificantDtorParser {
+    const PATH: &[Symbol] = &[sym::rustc_insignificant_dtor];
+    const ON_DUPLICATE: OnDuplicate<S> = OnDuplicate::Error;
+    const ALLOWED_TARGETS: AllowedTargets = AllowedTargets::AllowList(&[
+        Allow(Target::Enum),
+        Allow(Target::Struct),
+        Allow(Target::ForeignTy),
+    ]);
+    const CREATE: fn(Span) -> AttributeKind = |_| AttributeKind::RustcInsignificantDtor;
+}
+
 pub(crate) struct RustcEffectiveVisibilityParser;
 
 impl<S: Stage> NoArgsAttributeParser<S> for RustcEffectiveVisibilityParser {
diff --git a/compiler/rustc_attr_parsing/src/context.rs b/compiler/rustc_attr_parsing/src/context.rs
index ad39b0ec26d9..7921928ce7c5 100644
--- a/compiler/rustc_attr_parsing/src/context.rs
+++ b/compiler/rustc_attr_parsing/src/context.rs
@@ -270,6 +270,7 @@ attribute_parsers!(
         Single<WithoutArgs<RustcEffectiveVisibilityParser>>,
         Single<WithoutArgs<RustcHasIncoherentInherentImplsParser>>,
         Single<WithoutArgs<RustcHiddenTypeOfOpaquesParser>>,
+        Single<WithoutArgs<RustcInsignificantDtorParser>>,
         Single<WithoutArgs<RustcIntrinsicConstStableIndirectParser>>,
         Single<WithoutArgs<RustcIntrinsicParser>>,
         Single<WithoutArgs<RustcLintOptTyParser>>,
diff --git a/compiler/rustc_hir/src/attrs/data_structures.rs b/compiler/rustc_hir/src/attrs/data_structures.rs
index 79452913c259..aaeebcc5c66d 100644
--- a/compiler/rustc_hir/src/attrs/data_structures.rs
+++ b/compiler/rustc_hir/src/attrs/data_structures.rs
@@ -1120,6 +1120,9 @@ pub enum AttributeKind {
     /// Represents `#[rustc_if_this_changed]`
     RustcIfThisChanged(Span, Option<Symbol>),
 
+    /// Represents `#[rustc_insignificant_dtor]`
+    RustcInsignificantDtor,
+
     /// Represents `#[rustc_intrinsic]`
     RustcIntrinsic,
 
diff --git a/compiler/rustc_hir/src/attrs/encode_cross_crate.rs b/compiler/rustc_hir/src/attrs/encode_cross_crate.rs
index ba351d80544c..4fb20599a026 100644
--- a/compiler/rustc_hir/src/attrs/encode_cross_crate.rs
+++ b/compiler/rustc_hir/src/attrs/encode_cross_crate.rs
@@ -118,6 +118,7 @@ impl AttributeKind {
             RustcHasIncoherentInherentImpls => Yes,
             RustcHiddenTypeOfOpaques => No,
             RustcIfThisChanged(..) => No,
+            RustcInsignificantDtor => Yes,
             RustcIntrinsic => Yes,
             RustcIntrinsicConstStableIndirect => No,
             RustcLayout(..) => No,
diff --git a/compiler/rustc_passes/src/check_attr.rs b/compiler/rustc_passes/src/check_attr.rs
index 6c4b76a08ad2..2f1695f0712a 100644
--- a/compiler/rustc_passes/src/check_attr.rs
+++ b/compiler/rustc_passes/src/check_attr.rs
@@ -313,6 +313,7 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                     | AttributeKind::RustcHasIncoherentInherentImpls
                     | AttributeKind::RustcHiddenTypeOfOpaques
                     | AttributeKind::RustcIfThisChanged(..)
+                    | AttributeKind::RustcInsignificantDtor
                     | AttributeKind::RustcIntrinsic
                     | AttributeKind::RustcIntrinsicConstStableIndirect
                     | AttributeKind::RustcLayout(..)
@@ -386,7 +387,6 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                             | sym::default_lib_allocator
                             | sym::rustc_diagnostic_item
                             | sym::rustc_no_mir_inline
-                            | sym::rustc_insignificant_dtor
                             | sym::rustc_nonnull_optimization_guaranteed
                             | sym::rustc_inherit_overflow_checks
                             | sym::rustc_trivial_field_reads
diff --git a/compiler/rustc_ty_utils/src/needs_drop.rs b/compiler/rustc_ty_utils/src/needs_drop.rs
index 0ef435b1a0e2..06eef7e95145 100644
--- a/compiler/rustc_ty_utils/src/needs_drop.rs
+++ b/compiler/rustc_ty_utils/src/needs_drop.rs
@@ -1,13 +1,14 @@
 //! Check whether a type has (potentially) non-trivial drop glue.
 
 use rustc_data_structures::fx::FxHashSet;
+use rustc_hir::attrs::AttributeKind;
 use rustc_hir::def_id::DefId;
+use rustc_hir::find_attr;
 use rustc_hir::limit::Limit;
 use rustc_middle::bug;
 use rustc_middle::query::Providers;
 use rustc_middle::ty::util::{AlwaysRequiresDrop, needs_drop_components};
 use rustc_middle::ty::{self, EarlyBinder, GenericArgsRef, Ty, TyCtxt};
-use rustc_span::sym;
 use tracing::{debug, instrument};
 
 use crate::errors::NeedsDropOverflow;
@@ -396,8 +397,7 @@ fn adt_consider_insignificant_dtor<'tcx>(
     tcx: TyCtxt<'tcx>,
 ) -> impl Fn(ty::AdtDef<'tcx>) -> Option<DtorType> {
     move |adt_def: ty::AdtDef<'tcx>| {
-        let is_marked_insig = tcx.has_attr(adt_def.did(), sym::rustc_insignificant_dtor);
-        if is_marked_insig {
+        if find_attr!(tcx.get_all_attrs(adt_def.did()), AttributeKind::RustcInsignificantDtor) {
             // In some cases like `std::collections::HashMap` where the struct is a wrapper around
             // a type that is a Drop type, and the wrapped type (eg: `hashbrown::HashMap`) lies
             // outside stdlib, we might choose to still annotate the wrapper (std HashMap) with