[clang] [Clang] Avoid querying tag definitions for invalid DeclSpecs (PR #210085)

[Osama Abdelkader via cfe-commits]

https://github.com/osamakader updated https://github.com/llvm/llvm-project/pull/210085

>From ae6df644f97e3f2347ec992194385949324e55e0 Mon Sep 17 00:00:00 2001
From: Osama Abdelkader <osama.abdelkader at gmail.com>
Date: Thu, 16 Jul 2026 17:38:30 +0200
Subject: [PATCH 1/4] [Clang] Avoid querying tag definitions for invalid
 DeclSpecs

Guard hasTagDefinition() against invalid type-specifier state so recovery from invalid auto/tag combinations does not assert.

Signed-off-by: Osama Abdelkader <osama.abdelkader at gmail.com>
---
 clang/lib/Sema/DeclSpec.cpp       | 2 +-
 clang/test/SemaCXX/auto-cxx0x.cpp | 3 +++
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/clang/lib/Sema/DeclSpec.cpp b/clang/lib/Sema/DeclSpec.cpp
index 4d20657d5e517..9df12d0c4ce75 100644
--- a/clang/lib/Sema/DeclSpec.cpp
+++ b/clang/lib/Sema/DeclSpec.cpp
@@ -431,7 +431,7 @@ void DeclSpec::forEachQualifier(
 }
 
 bool DeclSpec::hasTagDefinition() const {
-  if (!TypeSpecOwned)
+  if (!TypeSpecOwned || !isDeclRep((TST)TypeSpecType))
     return false;
   return cast<TagDecl>(getRepAsDecl())->isCompleteDefinition();
 }
diff --git a/clang/test/SemaCXX/auto-cxx0x.cpp b/clang/test/SemaCXX/auto-cxx0x.cpp
index fa953f35723ef..ff2c98fce7523 100644
--- a/clang/test/SemaCXX/auto-cxx0x.cpp
+++ b/clang/test/SemaCXX/auto-cxx0x.cpp
@@ -14,6 +14,9 @@ void f() {
 struct PR209000 {
 } auto; // expected-error {{'auto' cannot be combined with a type specifier}}
 
+auto union { // expected-error {{cannot combine with previous 'auto' declaration specifier}}
+} foo<>; // expected-error {{no template named 'foo'}}
+
 typedef auto PR25449(); // expected-error {{'auto' not allowed in typedef}}
 
 thread_local auto x; // expected-error {{requires an initializer}}

>From da2d9c93b52e457fb88f303f07aabfd1dc468a4b Mon Sep 17 00:00:00 2001
From: Osama Abdelkader <osama.abdelkader at gmail.com>
Date: Mon, 20 Jul 2026 15:51:48 +0200
Subject: [PATCH 2/4] [Clang] update ReleaseNotes with #GH210014 fix

Signed-off-by: Osama Abdelkader <osama.abdelkader at gmail.com>
---
 clang/docs/ReleaseNotes.md | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/clang/docs/ReleaseNotes.md b/clang/docs/ReleaseNotes.md
index 052838ef0af0d..2bb80455b85a6 100644
--- a/clang/docs/ReleaseNotes.md
+++ b/clang/docs/ReleaseNotes.md
@@ -155,6 +155,9 @@ latest release, please see the [Clang Web Site](https://clang.llvm.org) or the
 
 #### Miscellaneous Clang Crashes Fixed
 
+- Fixed a crash when parsing invalid C++ declarations that combine `auto` with
+  an anonymous tag definition. (#GH210014)
+
 ### OpenACC Specific Changes
 
 ### OpenCL Specific Changes

>From fb38c9c7e0e631cf09040c6f743eaa69cc9a93b2 Mon Sep 17 00:00:00 2001
From: Osama Abdelkader <osama.abdelkader at gmail.com>
Date: Tue, 21 Jul 2026 15:48:51 +0200
Subject: [PATCH 3/4] [Clang] update test case #GH210014

Signed-off-by: Osama Abdelkader <osama.abdelkader at gmail.com>
---
 clang/test/SemaCXX/auto-cxx0x.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/clang/test/SemaCXX/auto-cxx0x.cpp b/clang/test/SemaCXX/auto-cxx0x.cpp
index ff2c98fce7523..bdb154b8600b4 100644
--- a/clang/test/SemaCXX/auto-cxx0x.cpp
+++ b/clang/test/SemaCXX/auto-cxx0x.cpp
@@ -15,7 +15,7 @@ struct PR209000 {
 } auto; // expected-error {{'auto' cannot be combined with a type specifier}}
 
 auto union { // expected-error {{cannot combine with previous 'auto' declaration specifier}}
-} foo<>; // expected-error {{no template named 'foo'}}
+} foo<>(); // expected-error {{no template named 'foo'}}
 
 typedef auto PR25449(); // expected-error {{'auto' not allowed in typedef}}
 

>From e551f86c7d91ad3179d696e3bd7db8b1686d7dcf Mon Sep 17 00:00:00 2001
From: Osama Abdelkader <osama.abdelkader at gmail.com>
Date: Tue, 21 Jul 2026 16:09:55 +0200
Subject: [PATCH 4/4] [Clang] update test case #GH210014 expectations

Signed-off-by: Osama Abdelkader <osama.abdelkader at gmail.com>
---
 clang/test/SemaCXX/auto-cxx0x.cpp | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/clang/test/SemaCXX/auto-cxx0x.cpp b/clang/test/SemaCXX/auto-cxx0x.cpp
index bdb154b8600b4..7b84da97b464c 100644
--- a/clang/test/SemaCXX/auto-cxx0x.cpp
+++ b/clang/test/SemaCXX/auto-cxx0x.cpp
@@ -15,7 +15,8 @@ struct PR209000 {
 } auto; // expected-error {{'auto' cannot be combined with a type specifier}}
 
 auto union { // expected-error {{cannot combine with previous 'auto' declaration specifier}}
-} foo<>(); // expected-error {{no template named 'foo'}}
+} foo<>(); // expected-error {{no template named 'foo'}} \
+           // expected-error {{expected unqualified-id}}
 
 typedef auto PR25449(); // expected-error {{'auto' not allowed in typedef}}