[Clang] prevent setting default lexical access specifier for missing primary declarations

[a-tarasyuk]

Fixes #112208

---

This PR resolves a crash triggered by a forward reference to an enum type in a function parameter list. The fix includes setting Invalid when TagUseKind is Declaration to ensure correct error handling.

[llvmbot]

@llvm/pr-subscribers-clang

Author: Oleksandr T. (a-tarasyuk)

Changes

Fixes #112208

---

Full diff: https://github.com/llvm/llvm-project/pull/112424.diff

3 Files Affected:

• (modified) clang/docs/ReleaseNotes.rst (+2)
• (modified) clang/lib/Sema/SemaAccess.cpp (+2-1)
• (modified) clang/test/SemaCXX/enum.cpp (+8)

diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 817e3abef8d566..64ffdcde045a3a 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -517,6 +517,8 @@ Bug Fixes to C++ Support
   certain situations. (#GH47400), (#GH90896)
 - Fix erroneous templated array size calculation leading to crashes in generated code. (#GH41441)
 - During the lookup for a base class name, non-type names are ignored. (#GH16855)
+- Fixed an assertion failure when the default lexical access specifier was set for missing
+  primary declarations. (#GH112208)
 
 Bug Fixes to AST Handling
 ^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/clang/lib/Sema/SemaAccess.cpp b/clang/lib/Sema/SemaAccess.cpp
index df6edb21a50dee..8b4a5b70669d84 100644
--- a/clang/lib/Sema/SemaAccess.cpp
+++ b/clang/lib/Sema/SemaAccess.cpp
@@ -39,7 +39,8 @@ bool Sema::SetMemberAccessSpecifier(NamedDecl *MemberDecl,
                                     AccessSpecifier LexicalAS) {
   if (!PrevMemberDecl) {
     // Use the lexical access specifier.
-    MemberDecl->setAccess(LexicalAS);
+    if (LexicalAS != AS_none)
+      MemberDecl->setAccess(LexicalAS);
     return false;
   }
 
diff --git a/clang/test/SemaCXX/enum.cpp b/clang/test/SemaCXX/enum.cpp
index 9c398cc8da886c..44042d8bf5cfc8 100644
--- a/clang/test/SemaCXX/enum.cpp
+++ b/clang/test/SemaCXX/enum.cpp
@@ -143,3 +143,11 @@ struct PR28903 {
     })
   };
 };
+
+namespace GH112208 {
+class C {
+  enum E { e = 0 };
+  void f(int, enum E;); // expected-error {{ISO C++ forbids forward references to 'enum' types}} \
+                        // expected-error {{unexpected ';' before ')'}}
+};
+}

[shafik]

Assuming it passes the test LGTM

[zyn0217]

Thanks!