Switch expression can erroneously generate error about unreachable case when using "if" in case pattern

[jaccomoc]

This currently fails:

switch (3) {
  int if it == 3 -> '3'
  int                -> 'something else'
}

with this error:

io.jactl.CompileError: Unreachable switch case (covered by a previous case) @ line 3, column 3
  int -> 'something else'
  ^