BinaryOp::reverse does nothing but is used with the expectation of doing something

[pikaju]

The function BinaryOp::reverse currently does nothing as far as I can tell:

toasty/crates/toasty-core/src/stmt/op_binary.rs

Line 27 in 8d1636f

pub fn reverse(&mut self) {

However, code in IndexMatch expects this function to do something:

toasty/crates/toasty/src/engine/index/index_match.rs

Line 65 in 8d1636f

let mut op = e.op;

toasty/crates/toasty/src/engine/index/index_match.rs

Line 329 in 8d1636f

op.reverse();

The tests pass despite this. I tried actually reversing the operator from Lt to Gt, LetoGe`, etc, and as a result the tests failed.

[claymcleod]

It's worth mentioning that I introduced a commute() function here—this appears to be a full implementation of what reverse() was meant to be (maybe?).