[clang] Improved isSimpleTypeSpecifier (llvm#79037)

- Sema::isSimpleTypeSpecifier return true for _Bool in c99 (currently
returns false for _Bool, regardless of C dialect). (Fixes llvm#72203)
- replace the logic with a check for simple types and a proper check for
a valid keyword in the appropriate dialect

Co-authored-by: Carl Peto <CPeto@becrypt.com>

clang/include/clang/Sema/Sema.h

@@ -2683,7 +2683,7 @@ class Sema final {
 
   void DiagnoseUseOfUnimplementedSelectors();
 
-  bool isSimpleTypeSpecifier(tok::TokenKind Kind) const;
+  bool isSimpleTypeSpecifier(const Token &Tok) const;
 
   ParsedType getTypeName(const IdentifierInfo &II, SourceLocation NameLoc,
                          Scope *S, CXXScopeSpec *SS = nullptr,

clang/lib/Parse/ParseExpr.cpp

@@ -1609,7 +1609,7 @@ ExprResult Parser::ParseCastExpression(CastParseKind ParseKind,
       if (TryAnnotateTypeOrScopeToken())
         return ExprError();
 
-      if (!Actions.isSimpleTypeSpecifier(Tok.getKind()))
+      if (!Actions.isSimpleTypeSpecifier(Tok))
         // We are trying to parse a simple-type-specifier but might not get such
         // a token after error recovery.
         return ExprError();

clang/lib/Parse/ParseObjc.cpp

@@ -2971,7 +2971,7 @@ bool Parser::ParseObjCXXMessageReceiver(bool &IsExpr, void *&TypeOrExpr) {
                   tok::annot_cxxscope))
     TryAnnotateTypeOrScopeToken();
 
-  if (!Actions.isSimpleTypeSpecifier(Tok.getKind())) {
+  if (!Actions.isSimpleTypeSpecifier(Tok)) {
     //   objc-receiver:
     //     expression
     // Make sure any typos in the receiver are corrected or diagnosed, so that

clang/lib/Sema/SemaDecl.cpp

@@ -128,10 +128,13 @@ class TypeNameValidatorCCC final : public CorrectionCandidateCallback {
 } // end anonymous namespace
 
 /// Determine whether the token kind starts a simple-type-specifier.
-bool Sema::isSimpleTypeSpecifier(tok::TokenKind Kind) const {
-  switch (Kind) {
-  // FIXME: Take into account the current language when deciding whether a
-  // token kind is a valid type specifier
+bool Sema::isSimpleTypeSpecifier(const Token &Tok) const {
+  switch (Tok.getKind()) {
+  case tok::annot_typename:
+  case tok::annot_decltype:
+  case tok::annot_pack_indexing_type:
+    return true;
+
   case tok::kw_short:
   case tok::kw_long:
   case tok::kw___int64:
@@ -150,31 +153,23 @@ bool Sema::isSimpleTypeSpecifier(tok::TokenKind Kind) const {
   case tok::kw___ibm128:
   case tok::kw_wchar_t:
   case tok::kw_bool:
+  case tok::kw__Bool:
   case tok::kw__Accum:
   case tok::kw__Fract:
   case tok::kw__Sat:
 #define TRANSFORM_TYPE_TRAIT_DEF(_, Trait) case tok::kw___##Trait:
 #include "clang/Basic/TransformTypeTraits.def"
   case tok::kw___auto_type:
-    return true;
-
-  case tok::annot_typename:
   case tok::kw_char16_t:
   case tok::kw_char32_t:
   case tok::kw_typeof:
-  case tok::annot_decltype:
-  case tok::annot_pack_indexing_type:
   case tok::kw_decltype:
-    return getLangOpts().CPlusPlus;
-
   case tok::kw_char8_t:
-    return getLangOpts().Char8;
+    return Tok.getIdentifierInfo()->isKeyword(getLangOpts());
 
   default:
-    break;
+    return false;
   }
-
-  return false;
 }
 
 namespace {