[clang] [clang]fix ppcaching assertion gh186582 (PR #187370)

[via cfe-commits]

https://github.com/Serosh-commits updated https://github.com/llvm/llvm-project/pull/187370

>From e9b8aeea0bf90303d30387d762d69ff29e40d2fa Mon Sep 17 00:00:00 2001
From: Serosh-commits <janmejayapanda400 at gmail.com>
Date: Thu, 19 Mar 2026 00:57:24 +0530
Subject: [PATCH] test update

---
 clang/docs/ReleaseNotes.rst      | 7 ++++---
 clang/lib/Parse/ParseExprCXX.cpp | 4 ++--
 clang/test/Parser/gh186582.cpp   | 6 ++++++
 3 files changed, 12 insertions(+), 5 deletions(-)
 create mode 100644 clang/test/Parser/gh186582.cpp

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 613d87668be18..91fbeb82aa04e 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -227,6 +227,7 @@ Bug Fixes in This Version
 - Fixed atomic boolean compound assignment; the conversion back to atomic bool would be miscompiled. (#GH33210)
 
 - Fixed a failed assertion in the preprocessor when ``__has_embed`` parameters are missing parentheses. (#GH175088)
+- Fixed an assertion failure in the preprocessor when encountering ``::template operator`` during tentative parsing. (#GH186582)
 
 - Fix lifetime extension of temporaries in for-range-initializers in templates. (#GH165182)
 - Fixed a preprocessor crash in ``__has_cpp_attribute`` on incomplete scoped attributes. (#GH178098)
@@ -343,7 +344,7 @@ AST Matchers
 
 clang-format
 ------------
-- Add ``ObjCSpaceAfterMethodDeclarationPrefix`` option to control space between the 
+- Add ``ObjCSpaceAfterMethodDeclarationPrefix`` option to control space between the
   '-'/'+' and the return type in Objective-C method declarations
 
 libclang
@@ -378,8 +379,8 @@ Python Binding Changes
   Affected methods: ``isKindOptional``, ``isKindTypedText``, ``isKindPlaceHolder``,
   ``isKindInformative`` and ``isKindResultType``.
 - Add a deprecation warning to ``CodeCompletionResults.results``.
-  This property will become an implementation detail with changed behavior in a 
-  future release and should not be used directly.. Existing uses of 
+  This property will become an implementation detail with changed behavior in a
+  future release and should not be used directly.. Existing uses of
   ``CodeCompletionResults.results`` should be changed to directly use
   ``CodeCompletionResults``: it nows supports ``__len__`` and ``__getitem__``,
   so it can be used the same as ``CodeCompletionResults.results``.
diff --git a/clang/lib/Parse/ParseExprCXX.cpp b/clang/lib/Parse/ParseExprCXX.cpp
index 842b52375eb14..b50b5c383b961 100644
--- a/clang/lib/Parse/ParseExprCXX.cpp
+++ b/clang/lib/Parse/ParseExprCXX.cpp
@@ -286,7 +286,7 @@ bool Parser::ParseOptionalCXXScopeSpecifier(
         // we already annotated the template-id.
         if (ParseUnqualifiedIdOperator(SS, EnteringContext, ObjectType,
                                        TemplateName)) {
-          TPA.Commit();
+          TPA.Revert();
           break;
         }
 
@@ -295,7 +295,7 @@ bool Parser::ParseOptionalCXXScopeSpecifier(
           Diag(TemplateName.getSourceRange().getBegin(),
                diag::err_id_after_template_in_nested_name_spec)
             << TemplateName.getSourceRange();
-          TPA.Commit();
+          TPA.Revert();
           break;
         }
       } else {
diff --git a/clang/test/Parser/gh186582.cpp b/clang/test/Parser/gh186582.cpp
new file mode 100644
index 0000000000000..c5094724ba6e5
--- /dev/null
+++ b/clang/test/Parser/gh186582.cpp
@@ -0,0 +1,6 @@
+// RUN: %clang_cc1 -fsyntax-only -std=c++23 -verify %s
+
+a(   ::template operator // expected-error {{a type specifier is required for all declarations}} \
+                         // expected-error {{expected ';' after top level declarator}}
+// expected-error at 6 {{expected a type}}
+// expected-error {{expected unqualified-id}}