Check if the target types are equal instead of the types themselves.

Author: DanielRosenwasser

src/compiler/checker.ts

@@ -6894,7 +6894,7 @@ namespace ts {
         // subtype of T but not structurally identical to T. This specifically means that two distinct but
         // structurally identical types (such as two classes) are not considered instances of each other.
         function isTypeInstanceOf(source: Type, target: Type): boolean {
-            return source === target || isTypeSubtypeOf(source, target) && !isTypeIdenticalTo(source, target);
+            return getTargetType(source) === getTargetType(target) || isTypeSubtypeOf(source, target) && !isTypeIdenticalTo(source, target);
         }
 
         /**