打字稿2.8.3：没有共同属性的联合类型

Question

The following worked fine on Typescript 2.3.5 but it does not anymore on 2.8.3 .

class A {
       variableA: string;
   }
   class B {
       variableB: number;
   }
   class C {
       variableC: boolean;
   }
   type TYPES = A | B | C;

   function doStuff(types: TYPES) {
       switch (types) {
       case A: // error
           break;
       case B: // error
           break;
       case C: // error
           break;
       }
   }
   doStuff(A); // error

[ts] Argument of type 'typeof A' is not assignable to parameter of type 'TYPES'. Type 'typeof A' is not assignable to type 'C'. Property 'variableC' is missing in type 'typeof A'.

How do I change this structure so it works again?

Answer 1

A type designates an instance of A/B/C class, while types value is A/B/C class itself.

It should be:

   type TYPES = typeof A | typeof B | typeof C;

   function doStuff(types: TYPES) {
       switch (types) {
       case A:
           break;
       case B:
           break;
       case C:
           break;
       }
   }
   doStuff(A);