Issue Description:

enum Demo {
  case foo
  case bar
  case baz
}


func ~= (pattern: Demo, value: String) -> Bool {
  false
}


func a() {
  switch "" {
  case .foo, .bar:
    break
  case Demo.baz:   // < ERROR: Enum case 'baz' is not a member of type 'String'
    break
  default:
    break
  }
}

When referring to cases as ".foo" or ".bar", all is well. However, when using the type-qualified spelling "Demo.baz", the code fails to compile. Moreover, the diagnostic tells us that it... expects 'baz' to exist on String... but it knows its an enum case, soo... it must have seen the definition in 'Demo'? So why is it looking in String?

Weirdness.