[Clang] Fix crash in Parser::ParseDirectDeclarator by adding check that token is not an annotation token

[shafik]

Summary

In Parser::ParseDirectDeclarator(...) in some cases ill-formed code can cause an annotation token to end up where it was not expected. The fix is to add a !Tok.isAnnotation() guard before attempting to access identifier info.

This fixes:

https://github.com/llvm/llvm-project/issues/64836

[nridge]

I'm not well versed in the parser code, but the fix clearly avoids the assertion in getIdentifierInfo(), and both @aaron.ballman and @rjmccall indicated in the issue discussion that this fix is appropriate, so I will take the liberty of approving this.

[shafik]

• Add release note

clang/lib/Parse/ParseDecl.cpp

if (Tok.is(tok::l_paren)) {
     if (Tok.getKind() == tok::annot_pragma_parser_crash)
       LLVM_BUILTIN_TRAP;
     if (Tok.is(tok::l_square))
       return ParseMisplacedBracketDeclarator(D);
     if (D.getContext() == DeclaratorContext::Member) {
       // Objective-C++: Detect C++ keywords and try to prevent further errors by
       // treating these keyword as valid member names.
       if (getLangOpts().ObjC && getLangOpts().CPlusPlus &&
-          Tok.getIdentifierInfo() &&
+          !Tok.isAnnotation() && Tok.getIdentifierInfo() &&
           Tok.getIdentifierInfo()->isCPlusPlusKeyword(getLangOpts())) {
         Diag(getMissingDeclaratorIdLoc(D, Tok.getLocation()),
              diag::err_expected_member_name_or_semi_objcxx_keyword)
             << Tok.getIdentifierInfo()
             << (D.getDeclSpec().isEmpty() ? SourceRange()
                                           : D.getDeclSpec().getSourceRange());
         D.SetIdentifier(Tok.getIdentifierInfo(), Tok.getLocation());
         D.SetRangeEnd(Tok.getLocation());

clang/test/Parser/gh64836.cpp

+// RUN: %clang_cc1 -fsyntax-only -verify -xobjective-c++-header %s
+
+template <typename, typename>
+class C {};
+
+class B {
+  p // expected-error {{unknown type name 'p'}}
+ private: // expected-error {{'private' is a keyword in Objective-C++}}
+  void f() {} // expected-error {{expected '(' for function-style cast or type construction}}
+  C<int, decltype(f)> c; // expected-error {{use of undeclared identifier 'f'}}
+  // expected-error@-1 {{expected member name}}
+};