When subtracting an Instant from another, the function will panick when `RHS > self`, but the error message confusingly displays a different error:
```rust
let i = Instant::now();
let other = Instant::now();
if other > i {
println!("{:?}", i - other);
}
```
This results in a panic:
```
thread 'test_instant' panicked at 'other was less than the current instant', libstd/sys/unix/time.rs:292:17
```
pub fn sub_instant(&self, other: &Instant) -> Duration {
self.t.sub_timespec(&other.t).unwrap_or_else(|_| {
- panic!("other was less than the current instant")
+ panic!("other was greater than the current instant")
})
}