[NFC][CLANG] Fix issue with dereference null return value in EvaluateBuiltinClassifyType()

[Manna]

Summary

This patch uses cast instead of dyn_cast which will assert if the type doesn't match.

[erichkeane]

clang/lib/AST/ExprConstant.cpp

11292–11293

I don't think this is right. BT is only dereferenced in the event that CanTy's type class is "Builtin". We COULD introduce a scope around the Type::Builtin type and move this there, but this will now assert any time that CanTy is a Pointer, auto, etc.

[Manna]

Thank you @erichkeane for reviews! I have updated patch to avoid the regression.

[erichkeane]

This looks right for me.

[Manna]

Fix clang-format error

clang/lib/AST/ExprConstant.cpp

 };
 
 /// EvaluateBuiltinClassifyType - Evaluate __builtin_classify_type the same way
 /// as GCC.
 static GCCTypeClass
 EvaluateBuiltinClassifyType(QualType T, const LangOptions &LangOpts) {
   assert(!T->isDependentType() && "unexpected dependent type");
 
   QualType CanTy = T.getCanonicalType();
-  const BuiltinType *BT = dyn_cast<BuiltinType>(CanTy);
 
   switch (CanTy->getTypeClass()) {
 #define TYPE(ID, BASE)
 #define DEPENDENT_TYPE(ID, BASE) case Type::ID:
 #define NON_CANONICAL_TYPE(ID, BASE) case Type::ID:
 #define NON_CANONICAL_UNLESS_DEPENDENT_TYPE(ID, BASE) case Type::ID:
 #include "clang/AST/TypeNodes.inc"
   case Type::Auto:
   case Type::DeducedTemplateSpecialization:
       llvm_unreachable("unexpected non-canonical or dependent type");
 
   case Type::Builtin:
-    switch (BT->getKind()) {
+      switch (cast<BuiltinType>(CanTy)->getKind()) {
 #define BUILTIN_TYPE(ID, SINGLETON_ID)
 #define SIGNED_TYPE(ID, SINGLETON_ID) \
     case BuiltinType::ID: return GCCTypeClass::Integer;
 #define FLOATING_TYPE(ID, SINGLETON_ID) \
     case BuiltinType::ID: return GCCTypeClass::RealFloat;
 #define PLACEHOLDER_TYPE(ID, SINGLETON_ID) \
     case BuiltinType::ID: break;
 #include "clang/AST/BuiltinTypes.def"