Add isTypeErasedGenericClassType to TypeBase.

NFC.

Author: aschwaighofer

include/swift/AST/Types.h

@@ -714,7 +714,10 @@ class alignas(1 << TypeAlignInBits) TypeBase {
   /// class-bounded existential type whose required conformances are
   /// all @objc.  Such types are compatible with ObjC.
   bool isObjCExistentialType();
-  
+
+  // // Is this an ObjC generic class.
+  bool isTypeErasedGenericClassType();
+
   /// Determines whether this type is an existential type with a class protocol
   /// bound.
   bool isClassExistentialType();

lib/AST/Type.cpp

@@ -337,6 +337,10 @@ bool TypeBase::isObjCExistentialType() {
   return getCanonicalType().isObjCExistentialType();
 }
 
+bool TypeBase::isTypeErasedGenericClassType() {
+  return getCanonicalType().isTypeErasedGenericClassType();
+}
+
 bool CanType::isObjCExistentialTypeImpl(CanType type) {
   if (!type.isExistentialType())
     return false;
@@ -4316,7 +4320,7 @@ case TypeKind::Id:
     bool changed = false;
     auto hasTypeErasedGenericClassType = [](Type ty) -> bool {
       return ty.findIf([](Type subType) -> bool {
-        if (subType->getCanonicalType().isTypeErasedGenericClassType())
+        if (subType->isTypeErasedGenericClassType())
           return true;
         else
           return false;