This module handles the following cases:
- `... >= ... + 1` and `... >= 1 + ...`
- `... - 1 >= ...` and `-1 + ... >= ...`
- `... + 1 <= ...` and `... + 1 <= ...`
- `... <= ... - 1` and `... <= -1 + ...`
Note: this only goes 1 level deep (i.e., does not constant-fold) and
does not currently simplify expressions. Examples of these
cases include:
```rust
let x = 1;
y >= y + x; // won't catch this case or any permutation
x + 1 >= y + 2; // won't catch this case
x + 1 - 1 >= y - 1 + 1; // WILL catch this case when it likely shouldn't
```
