[clang] [clang] fix parsing of late parsed attributes with delayed template parsing (PR #163483)

[Matheus Izvekov via cfe-commits]

https://github.com/mizvekov updated https://github.com/llvm/llvm-project/pull/163483

>From 43ac945821e354d8f3e84ece1be11de359a3aeb9 Mon Sep 17 00:00:00 2001
From: Matheus Izvekov <mizvekov at gmail.com>
Date: Tue, 14 Oct 2025 22:08:13 -0300
Subject: [PATCH] [clang] fix parsing of late parsed attributes with delayed
 template parsing

Besides ignoring the attribute, this would also cause a memory
leak.
---
 clang/docs/ReleaseNotes.rst                  |  3 ++-
 clang/lib/Parse/Parser.cpp                   | 11 +++++------
 clang/test/Parser/DelayedTemplateParsing.cpp | 13 +++++++++++--
 3 files changed, 18 insertions(+), 9 deletions(-)

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index db2b0f6fd5027..e4a66fad29c83 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -424,7 +424,8 @@ Bug Fixes to Attribute Support
   (#GH141504) and on types returned from indirect calls (#GH142453).
 - Fixes some late parsed attributes, when applied to function definitions, not being parsed
   in function try blocks, and some situations where parsing of the function body
-  is skipped, such as error recovery and code completion. (#GH153551)
+  is skipped, such as error recovery, code completion, and msvc-compatible delayed
+  template parsing. (#GH153551)
 - Using ``[[gnu::cleanup(some_func)]]`` where some_func is annotated with
   ``[[gnu::error("some error")]]`` now correctly triggers an error. (#GH146520)
 - Fix a crash when the function name is empty in the `swift_name` attribute. (#GH157075)
diff --git a/clang/lib/Parse/Parser.cpp b/clang/lib/Parse/Parser.cpp
index bbff627d46600..ec01faf446e8d 100644
--- a/clang/lib/Parse/Parser.cpp
+++ b/clang/lib/Parse/Parser.cpp
@@ -1272,7 +1272,7 @@ Decl *Parser::ParseFunctionDefinition(ParsingDeclarator &D,
   // tokens and store them for late parsing at the end of the translation unit.
   if (getLangOpts().DelayedTemplateParsing && Tok.isNot(tok::equal) &&
       TemplateInfo.Kind == ParsedTemplateKind::Template &&
-      Actions.canDelayFunctionBody(D)) {
+      LateParsedAttrs->empty() && Actions.canDelayFunctionBody(D)) {
     MultiTemplateParamsArg TemplateParameterLists(*TemplateInfo.TemplateParams);
 
     ParseScope BodyScope(this, Scope::FnScope | Scope::DeclScope |
@@ -1301,10 +1301,8 @@ Decl *Parser::ParseFunctionDefinition(ParsingDeclarator &D,
     }
     return DP;
   }
-  else if (CurParsedObjCImpl &&
-           !TemplateInfo.TemplateParams &&
-           (Tok.is(tok::l_brace) || Tok.is(tok::kw_try) ||
-            Tok.is(tok::colon)) &&
+  if (CurParsedObjCImpl && !TemplateInfo.TemplateParams &&
+      (Tok.is(tok::l_brace) || Tok.is(tok::kw_try) || Tok.is(tok::colon)) &&
       Actions.CurContext->isTranslationUnit()) {
     ParseScope BodyScope(this, Scope::FnScope | Scope::DeclScope |
                                    Scope::CompoundStmtScope);
@@ -1420,7 +1418,8 @@ Decl *Parser::ParseFunctionDefinition(ParsingDeclarator &D,
 
   // Late attributes are parsed in the same scope as the function body.
   if (LateParsedAttrs)
-    ParseLexedAttributeList(*LateParsedAttrs, Res, false, true);
+    ParseLexedAttributeList(*LateParsedAttrs, Res, /*EnterScope=*/false,
+                            /*OnDefinition=*/true);
 
   if (SkipFunctionBodies && (!Res || Actions.canSkipFunctionBody(Res)) &&
       trySkippingFunctionBody()) {
diff --git a/clang/test/Parser/DelayedTemplateParsing.cpp b/clang/test/Parser/DelayedTemplateParsing.cpp
index bcd286ae04492..072c7ce5162ee 100644
--- a/clang/test/Parser/DelayedTemplateParsing.cpp
+++ b/clang/test/Parser/DelayedTemplateParsing.cpp
@@ -43,10 +43,10 @@ void undeclared()
 
 }
 
-template <class T> void foo5() {} //expected-note {{previous definition is here}} 
+template <class T> void foo5() {} //expected-note {{previous definition is here}}
 template <class T> void foo5() {} // expected-error {{redefinition of 'foo5'}}
 
-              
+
 
 
 namespace PR11931 {
@@ -195,3 +195,12 @@ template <typename> struct PR38460_2 {
   }
 };
 template struct PR38460_2<int>;
+
+namespace LateParsedAttrs {
+  template <class>
+  void f(int a) __attribute__((__diagnose_if__(a > 0, "foo", "error"))) {}
+  // expected-note at -1 {{from 'diagnose_if' attribute on 'f<int>'}}
+  void g() {
+    f<int>(1); // expected-error {{foo}}
+  }
+} // namespace LateParsedAttrs