A macro for operator tests

[masak]

Never mind that we don't have a testing library in 007. We can stub one if we want.

This tweet felt inspiring. Not least because the author goes through a few iterations of his idea in order to arrive at the best possible macro.

(Edit: reproducing the Tweet below for completeness.)

This took a bit of macro voodoo, but I now have a pretty cool DSL for writing unit tests for my type checker. 😅 #rustlang

#[test]
fn add_operator() {
  operator_tests! {
    op: add,
    pass: [
      (int, int) -> int,
      (string, string) -> string
    ],
    fail: [
      (int, string),
      (string, int),
      (boolean, boolean)
    ]
  };
}

The final version is here. The implementation of that macro is just above.

I think it'd be interesting to think about what would be the 007 analogue of this, and how it'd be implemented as a macro.