[clang][Parser] Fix crash on malformed using declaration in constexpr function

[el-ev]

• Closes Clang frontend crashes on invalid usage of [[deprecated]] inside constexpr function #144264

[llvmbot]

@llvm/pr-subscribers-clang

Author: Iris Shi (el-ev)

Changes

• Closes #144264

---

Full diff: https://github.com/llvm/llvm-project/pull/144286.diff

2 Files Affected:

• (modified) clang/lib/Parse/ParseDeclCXX.cpp (+4)
• (added) clang/test/Parser/cxx-invalid-attr-in-constexpr-crash.cpp (+8)

diff --git a/clang/lib/Parse/ParseDeclCXX.cpp b/clang/lib/Parse/ParseDeclCXX.cpp
index f31c9265a0074..ed401c894f71c 100644
--- a/clang/lib/Parse/ParseDeclCXX.cpp
+++ b/clang/lib/Parse/ParseDeclCXX.cpp
@@ -760,6 +760,10 @@ Parser::DeclGroupPtrTy Parser::ParseUsingDeclaration(
 
     Decl *AD = ParseAliasDeclarationAfterDeclarator(
         TemplateInfo, UsingLoc, D, DeclEnd, AS, Attrs, &DeclFromDeclSpec);
+
+    if (!AD)
+      return nullptr;
+    
     return Actions.ConvertDeclToDeclGroup(AD, DeclFromDeclSpec);
   }
 
diff --git a/clang/test/Parser/cxx-invalid-attr-in-constexpr-crash.cpp b/clang/test/Parser/cxx-invalid-attr-in-constexpr-crash.cpp
new file mode 100644
index 0000000000000..82104779ca67e
--- /dev/null
+++ b/clang/test/Parser/cxx-invalid-attr-in-constexpr-crash.cpp
@@ -0,0 +1,8 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+
+// issue144264
+constexpr void test() 
+{ 
+    using TT = struct T[deprecated{}; 
+    // expected-error@-1 {{use of undeclared identifier 'deprecated'}}
+}

[github-actions]

✅ With the latest revision this PR passed the C/C++ code formatter.

[zwuis]

Please add a release note.

[el-ev]

Added.

[AaronBallman]

It looks like the test coverage was dropped in a recent commit.

[AaronBallman]

LGTM!