Allow return in a switch expression

[andrei-toterman]

This compiles just fine

void f(int x) {
  x = switch (x) {
      _ => throw Exception(),
  };
}

but this does not

void f(int x) {
  x = switch (x) {
      _ => return,
  };
}

But I think those should behave the same way, not assigning x any value and not caring about its type, since the function is about to be exited.

[julemand101]

I feel like this might be duplicate of #2025 or at least another case for that.

[andrei-toterman]

AH, yes, you are right. Thanks for pointing that out! I'll close this.