[clang] [clang] Reject 'auto' storage class with type specifier in C++ (PR #166004)

[Osama Abdelkader via cfe-commits]

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@@ -4095,11 +4095,22 @@ void Parser::ParseDeclarationSpecifiers(
     case tok::kw_auto:
       if (getLangOpts().CPlusPlus11 || getLangOpts().C23) {
         if (isKnownToBeTypeSpecifier(GetLookAheadToken(1))) {
-          isInvalid = DS.SetStorageClassSpec(Actions, DeclSpec::SCS_auto, Loc,
-                                             PrevSpec, DiagID, Policy);
-          if (!isInvalid && !getLangOpts().C23)
-            Diag(Tok, diag::ext_auto_storage_class)
-              << FixItHint::CreateRemoval(DS.getStorageClassSpecLoc());
+          // In C++ (not C23), 'auto' cannot be combined with a type specifier.
+          // However, OpenCL has its own error handling for this case.
----------------
osamakader wrote:

Without excluding OpenCL, the parser emitted our generic error "'auto' cannot be combined with a type specifier" instead of the OpenCL-specific one.

The test clang/test/SemaOpenCL/storageclass.cl expects:

expected-error{{C++ for OpenCL version 2021 does not support the 'auto' storage class specifier}}

or for OpenCL C:
expected-error-re{{OpenCL C version {{1.2|3.0}} does not support the 'auto' storage class specifier}}

If we don't exclude OpenCL, the parser emits our error and the test fails because it expects the OpenCL-specific message. Excluding OpenCL (!getLangOpts().OpenCLCPlusPlus) lets Sema emit the OpenCL-specific error.

https://github.com/llvm/llvm-project/pull/166004