Timer now throws an error in undefined case

[FraserLee]

Minimum Sample

use bevy::prelude::Timer;
use bevy::utils::Duration;

fn main() {
    let mut timer = Timer::from_seconds(0.0, true);
    timer.tick(Duration::from_millis(1000));
}

In 0.5 this will internally cause a nan f32, which will saturate to 0u32 and not error. As of #2362 it will throw an error and crash the program, since this piece of math has been converted to f128, which doesn't saturate on casts.

I'm a bit unsure whether to put in a PR to fix it, since the usecase here is fairly marginal (eg setting a timer to 0 duration to ensure it will hit on the next loop, etc). A fix here, on the other hand, could possibly have some performance penalties.

I'm fairly new to bevy, what's the move?

[DJMcNab]

A timer with 0 time is malformed. We should instead panic on new if the 0 Duration is added.

The use case of wanting the Timer to 'trigger next time' seems like it should just be stored in a piece of non-Timer state.

[mockersf]

Bevy already panic for a negative duration, it should panic for 0.0 too 👍

[DJMcNab]

As far as I know, Duration is by definition non-negative?

How do we panic on a negative duration?

[mockersf]

I mean, when calling from_seconds with a f32, Bevy creates a std Duration that panics for a negative value

[mockersf]

To have a Timer that is triggered at creation, I usually go with something like

    let duration = Duration::from_secs_f32(19.0);
    let mut new_timer = Timer::new(duration, true);
    new_timer.set_elapsed(duration);