else prong works even when it is exhaustive switch stage1

[g-w1]

This works:

pub fn main() void {
  const x = error.T;
  switch (x) {
    error.T => {},
    else => {}
  }
}

but it should not allow else because @TypeOf(x) == error { T } (according to @compileLog) so else is unreachable. I will try to fix this.

[Vexu]

This was intentionally left out when the error for unreachable else prongs was added (#5693) since it caused issues generic code.

[g-w1]

Ah, well ill let the other pr handle this, thanks.