[clang] [Clang] Fix getReturnTypeSourceRange() for trailing return types (PR #219101)

[Younan Zhang via cfe-commits]

https://github.com/zyn0217 created https://github.com/llvm/llvm-project/pull/219101

I'm not quite sure what that 'self-referential' meant and that logic doesn't seem to make much sense and it doesn't work for trailing return types.

Fixes #162649

>From 572d94bae50349793cf39d0b1fa373d426da5d32 Mon Sep 17 00:00:00 2001
From: Younan Zhang <zyn7109 at gmail.com>
Date: Thu, 27 Aug 2026 12:10:41 +0800
Subject: [PATCH] [Clang] Fix getReturnTypeSourceRange() for trailing return
 types

I'm not quite sure what that 'self-referential' meant and that logic
doesn't seem to make much sense and it doesn't work for trailing
return types.
---
 clang/docs/ReleaseNotes.md              | 7 +++++--
 clang/lib/AST/Decl.cpp                  | 5 +----
 clang/test/Sema/warn-main-return-type.c | 5 +++--
 3 files changed, 9 insertions(+), 8 deletions(-)

diff --git a/clang/docs/ReleaseNotes.md b/clang/docs/ReleaseNotes.md
index 8cc8eb5f80066..815e858b85360 100644
--- a/clang/docs/ReleaseNotes.md
+++ b/clang/docs/ReleaseNotes.md
@@ -486,9 +486,9 @@ features cannot lower the translation-unit ABI level;
   producing a spurious "no matching function" error with no candidate notes.
   (#GH210822)
 
-- Fixed a crash when module directive export module foo not following a 
+- Fixed a crash when module directive export module foo not following a
   semicolon and there are no rest pp-tokens in current module file. (#GH187771)
-  
+
 - Fixed a crash when a lambda parameter pack was given a default argument that
   is a pack expansion referencing an enclosing function's parameter pack (e.g.
   `[](Types... = args...) {}`). Clang now diagnoses the illegal default
@@ -544,6 +544,9 @@ features cannot lower the translation-unit ABI level;
   serialized PCH/AST files and `-Wunused-local-typedef` diagnostics
   non-reproducible across runs. (#GH209639)
 
+- `FunctionDecl::getReturnTypeSourceRange()` now returns correct source
+  location of a trailing return type. (#GH162649)
+
 #### Miscellaneous Bug Fixes
 
 #### Miscellaneous Clang Crashes Fixed
diff --git a/clang/lib/AST/Decl.cpp b/clang/lib/AST/Decl.cpp
index 0894097333d73..c9524dc82588a 100644
--- a/clang/lib/AST/Decl.cpp
+++ b/clang/lib/AST/Decl.cpp
@@ -4070,12 +4070,9 @@ SourceRange FunctionDecl::getReturnTypeSourceRange() const {
   if (!FTL)
     return SourceRange();
 
-  // Skip self-referential return types.
-  const SourceManager &SM = getASTContext().getSourceManager();
   SourceRange RTRange = FTL.getReturnLoc().getSourceRange();
   SourceLocation Boundary = getNameInfo().getBeginLoc();
-  if (RTRange.isInvalid() || Boundary.isInvalid() ||
-      !SM.isBeforeInTranslationUnit(RTRange.getEnd(), Boundary))
+  if (RTRange.isInvalid() || Boundary.isInvalid())
     return SourceRange();
 
   return RTRange;
diff --git a/clang/test/Sema/warn-main-return-type.c b/clang/test/Sema/warn-main-return-type.c
index 468a5de478e39..307395f70b4c0 100644
--- a/clang/test/Sema/warn-main-return-type.c
+++ b/clang/test/Sema/warn-main-return-type.c
@@ -43,8 +43,9 @@ fptr main(void) {
   return (fptr) 0;
 }
 
-// expected-error at +2 {{conflicting types for 'main}}
-// expected-warning at +1 {{return type of 'main' is not 'int'}}
+// expected-error at +3 {{conflicting types for 'main}}
+// expected-warning at +2 {{return type of 'main' is not 'int'}}
+// expected-note at +1 {{change return type to 'int'}}
 void *(*main(void))(int a) {
   return (fptr) 0;
 }