From ddcd55fa66354b7a3a7b524ba773a06bcbe4ae27 Mon Sep 17 00:00:00 2001
From: Jonathan Brouwer <jonathantbrouwer@gmail.com>
Date: Sun, 9 Nov 2025 17:54:22 +0100
Subject: [PATCH] Don't allow codegen attributes on trait methods

Signed-off-by: Jonathan Brouwer <jonathantbrouwer@gmail.com>
---
 compiler/rustc_attr_parsing/src/attributes/allow_unstable.rs  | 1 -
 compiler/rustc_attr_parsing/src/attributes/codegen_attrs.rs   | 3 +--
 compiler/rustc_attr_parsing/src/attributes/link_attrs.rs      | 3 +--
 compiler/rustc_attr_parsing/src/attributes/repr.rs            | 2 +-
 tests/ui/feature-gates/issue-43106-gating-of-builtin-attrs.rs | 4 ++++
 5 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/compiler/rustc_attr_parsing/src/attributes/allow_unstable.rs b/compiler/rustc_attr_parsing/src/attributes/allow_unstable.rs
index 79f7171cc0c8..7323db06a8f1 100644
--- a/compiler/rustc_attr_parsing/src/attributes/allow_unstable.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/allow_unstable.rs
@@ -61,7 +61,6 @@ impl<S: Stage> CombineAttributeParser<S> for AllowConstFnUnstableParser {
     const ALLOWED_TARGETS: AllowedTargets = AllowedTargets::AllowList(&[
         Allow(Target::Fn),
         Allow(Target::Method(MethodKind::Inherent)),
-        Allow(Target::Method(MethodKind::Trait { body: false })),
         Allow(Target::Method(MethodKind::Trait { body: true })),
         Allow(Target::Method(MethodKind::TraitImpl)),
     ]);
diff --git a/compiler/rustc_attr_parsing/src/attributes/codegen_attrs.rs b/compiler/rustc_attr_parsing/src/attributes/codegen_attrs.rs
index 7d3a7418f06c..477b8adc6729 100644
--- a/compiler/rustc_attr_parsing/src/attributes/codegen_attrs.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/codegen_attrs.rs
@@ -57,7 +57,6 @@ impl<S: Stage> NoArgsAttributeParser<S> for ColdParser {
         Allow(Target::Fn),
         Allow(Target::Method(MethodKind::Trait { body: true })),
         Allow(Target::Method(MethodKind::TraitImpl)),
-        Allow(Target::Method(MethodKind::Trait { body: false })),
         Allow(Target::Method(MethodKind::Inherent)),
         Allow(Target::ForeignFn),
         Allow(Target::Closure),
@@ -343,7 +342,7 @@ impl<S: Stage> NoArgsAttributeParser<S> for TrackCallerParser {
         Allow(Target::Method(MethodKind::Inherent)),
         Allow(Target::Method(MethodKind::Trait { body: true })),
         Allow(Target::Method(MethodKind::TraitImpl)),
-        Allow(Target::Method(MethodKind::Trait { body: false })),
+        Allow(Target::Method(MethodKind::Trait { body: false })), // `#[track_caller]` is inherited from trait methods
         Allow(Target::ForeignFn),
         Allow(Target::Closure),
         Warn(Target::MacroDef),
diff --git a/compiler/rustc_attr_parsing/src/attributes/link_attrs.rs b/compiler/rustc_attr_parsing/src/attributes/link_attrs.rs
index fe8f3578fe14..79143823bc68 100644
--- a/compiler/rustc_attr_parsing/src/attributes/link_attrs.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/link_attrs.rs
@@ -469,7 +469,6 @@ impl<S: Stage> SingleAttributeParser<S> for LinkSectionParser {
         Allow(Target::Static),
         Allow(Target::Fn),
         Allow(Target::Method(MethodKind::Inherent)),
-        Allow(Target::Method(MethodKind::Trait { body: false })),
         Allow(Target::Method(MethodKind::Trait { body: true })),
         Allow(Target::Method(MethodKind::TraitImpl)),
     ]);
@@ -587,12 +586,12 @@ impl<S: Stage> SingleAttributeParser<S> for LinkageParser {
     const ALLOWED_TARGETS: AllowedTargets = AllowedTargets::AllowList(&[
         Allow(Target::Fn),
         Allow(Target::Method(MethodKind::Inherent)),
-        Allow(Target::Method(MethodKind::Trait { body: false })),
         Allow(Target::Method(MethodKind::Trait { body: true })),
         Allow(Target::Method(MethodKind::TraitImpl)),
         Allow(Target::Static),
         Allow(Target::ForeignStatic),
         Allow(Target::ForeignFn),
+        Warn(Target::Method(MethodKind::Trait { body: false })), // Not inherited
     ]);
 
     const TEMPLATE: AttributeTemplate = template!(NameValueStr: [
diff --git a/compiler/rustc_attr_parsing/src/attributes/repr.rs b/compiler/rustc_attr_parsing/src/attributes/repr.rs
index 4520e4f5dbac..8df2f1d2c468 100644
--- a/compiler/rustc_attr_parsing/src/attributes/repr.rs
+++ b/compiler/rustc_attr_parsing/src/attributes/repr.rs
@@ -315,7 +315,7 @@ impl<S: Stage> AttributeParser<S> for AlignParser {
         Allow(Target::Method(MethodKind::Inherent)),
         Allow(Target::Method(MethodKind::Trait { body: true })),
         Allow(Target::Method(MethodKind::TraitImpl)),
-        Allow(Target::Method(MethodKind::Trait { body: false })),
+        Allow(Target::Method(MethodKind::Trait { body: false })), // `#[align]` is inherited from trait methods
         Allow(Target::ForeignFn),
     ]);
 
diff --git a/tests/ui/feature-gates/issue-43106-gating-of-builtin-attrs.rs b/tests/ui/feature-gates/issue-43106-gating-of-builtin-attrs.rs
index 4b5420a2ff8b..6716e78a7197 100644
--- a/tests/ui/feature-gates/issue-43106-gating-of-builtin-attrs.rs
+++ b/tests/ui/feature-gates/issue-43106-gating-of-builtin-attrs.rs
@@ -680,6 +680,10 @@ mod link_section {
     //~| HELP remove the attribute
     trait Tr {
         #[link_section = "1800"]
+        //~^ WARN attribute cannot be used on
+        //~| WARN previously accepted
+        //~| HELP can be applied to
+        //~| HELP remove the attribute
         fn inside_tr_no_default(&self);
 
         #[link_section = "1800"]