[clang] [Clang] fix assertion failure in ::template operator parsing (PR #194097)

[via cfe-commits]

https://github.com/Serosh-commits updated https://github.com/llvm/llvm-project/pull/194097

>From 64e7f41672c4b29243815b3ba9d502895f6d89dc Mon Sep 17 00:00:00 2001
From: Serosh-commits <janmejayapanda400 at gmail.com>
Date: Sat, 25 Apr 2026 06:50:32 +0530
Subject: [PATCH 1/2] [Clang][Parser] Fix assertion failure in ::template
 operator parsing (#GH186582)

---
 clang/docs/ReleaseNotes.rst      | 1 +
 clang/lib/Parse/ParseExprCXX.cpp | 8 ++++----
 clang/test/Parser/gh186582.cpp   | 8 ++++++++
 3 files changed, 13 insertions(+), 4 deletions(-)
 create mode 100644 clang/test/Parser/gh186582.cpp

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index c5c8c1fa12e7a..f4c5173028687 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -472,6 +472,7 @@ Improvements to Coverage Mapping
 Bug Fixes in This Version
 -------------------------
 
+- Fixed a preprocessor assertion failure triggered when parsing an invalid template-id starting with `::template operator`. (#GH186582)
 - Fixed atomic boolean compound assignment; the conversion back to atomic bool would be miscompiled. (#GH33210)
 - Correctly handle default template argument when establishing subsumption. (#GH188640)
 - Fixed a failed assertion in the preprocessor when ``__has_embed`` parameters are missing parentheses. (#GH175088)
diff --git a/clang/lib/Parse/ParseExprCXX.cpp b/clang/lib/Parse/ParseExprCXX.cpp
index 8903b638d49a4..39c61f4b5bf5c 100644
--- a/clang/lib/Parse/ParseExprCXX.cpp
+++ b/clang/lib/Parse/ParseExprCXX.cpp
@@ -287,8 +287,8 @@ bool Parser::ParseOptionalCXXScopeSpecifier(
         // we already annotated the template-id.
         if (ParseUnqualifiedIdOperator(SS, EnteringContext, ObjectType,
                                        TemplateName)) {
-          TPA.Commit();
-          break;
+          TPA.Revert();
+          return true;
         }
 
         if (TemplateName.getKind() != UnqualifiedIdKind::IK_OperatorFunctionId &&
@@ -296,8 +296,8 @@ bool Parser::ParseOptionalCXXScopeSpecifier(
           Diag(TemplateName.getSourceRange().getBegin(),
                diag::err_id_after_template_in_nested_name_spec)
             << TemplateName.getSourceRange();
-          TPA.Commit();
-          break;
+          TPA.Revert();
+          return true;
         }
       } else {
         TPA.Revert();
diff --git a/clang/test/Parser/gh186582.cpp b/clang/test/Parser/gh186582.cpp
new file mode 100644
index 0000000000000..d5b1102586833
--- /dev/null
+++ b/clang/test/Parser/gh186582.cpp
@@ -0,0 +1,8 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+
+a(   ::template operator
+// expected-error at -1 {{unknown type name 'a'}}
+// expected-error at -2 {{expected unqualified-id}}
+// expected-error at -3 {{expected ')'}}
+// expected-note at -4 {{to match this '('}}
+// expected-error@* 2{{expected a type}}

>From a102bf7026548eeb20c82e1a16574fff30bea909 Mon Sep 17 00:00:00 2001
From: Serosh-commits <janmejayapanda400 at gmail.com>
Date: Mon, 27 Apr 2026 19:12:04 +0530
Subject: [PATCH 2/2] [clang][docs] Move GH186582 release note to C++ bug fixes
 section

---
 clang/docs/ReleaseNotes.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index f4c5173028687..67843b99dfe45 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -472,7 +472,6 @@ Improvements to Coverage Mapping
 Bug Fixes in This Version
 -------------------------
 
-- Fixed a preprocessor assertion failure triggered when parsing an invalid template-id starting with `::template operator`. (#GH186582)
 - Fixed atomic boolean compound assignment; the conversion back to atomic bool would be miscompiled. (#GH33210)
 - Correctly handle default template argument when establishing subsumption. (#GH188640)
 - Fixed a failed assertion in the preprocessor when ``__has_embed`` parameters are missing parentheses. (#GH175088)
@@ -517,6 +516,7 @@ Bug Fixes to Attribute Support
 
 Bug Fixes to C++ Support
 ^^^^^^^^^^^^^^^^^^^^^^^^
+- Fixed a preprocessor assertion failure triggered when parsing an invalid template-id starting with ``::template operator``. (#GH186582)
 - Fixed a crash when a function template is defined as a non-template friend with a global scope qualifier. (#GH185341)
 - Clang now rejects constant template parameters with block pointer types, since these are not implemented anyway and would lead to crashes. (#GH189247)
 - Fixed a crash on error recovery when dealing with invalid templates. (#GH183075)