rust/library/core
Yuki Okushi c1f9d985d7
Rollup merge of #102271 - lopopolo:lopopolo/stabilize-duration-try-from-secs-float, r=dtolnay
Stabilize `duration_checked_float`

## Stabilization Report

This stabilization report is for a stabilization of `duration_checked_float`, tracking issue: https://github.com/rust-lang/rust/issues/83400.

### Implementation History

- https://github.com/rust-lang/rust/pull/82179
- https://github.com/rust-lang/rust/pull/90247
- https://github.com/rust-lang/rust/pull/96051
- Changed error type to `FromFloatSecsError` in https://github.com/rust-lang/rust/pull/90247
- https://github.com/rust-lang/rust/pull/96051 changes the rounding mode to round-to-nearest instead of truncate.

## API Summary

This stabilization report proposes the following API to be stabilized in `core`, along with their re-exports in `std`:

```rust
// core::time

impl Duration {
    pub const fn try_from_secs_f32(secs: f32) -> Result<Duration, TryFromFloatSecsError>;
    pub const fn try_from_secs_f64(secs: f64) -> Result<Duration, TryFromFloatSecsError>;
}

#[derive(Debug, Clone, PartialEq, Eq)]
pub struct TryFromFloatSecsError { ... }

impl core::fmt::Display for TryFromFloatSecsError { ... }
impl core::error::Error for TryFromFloatSecsError { ... }
```

These functions are made const unstable under `duration_consts_float`, tracking issue #72440.

There is an open question in the tracking issue around what the error type should be called which I was hoping to resolve in the context of an FCP.

In this stabilization PR, I have altered the name of the error type to `TryFromFloatSecsError`. In my opinion, the error type shares the name of the method (adjusted to accommodate both types of floats), which is consistent with other error types in `core`, `alloc` and `std` like `TryReserveError` and `TryFromIntError`.

## Experience Report

Code such as this is ready to be converted to a checked API to ensure it is panic free:

```rust
impl Time {
    pub fn checked_add_f64(&self, seconds: f64) -> Result<Self, TimeError> {
        // Fail safely during `f64` conversion to duration
        if seconds.is_nan() || seconds.is_infinite() {
            return Err(TzOutOfRangeError::new().into());
        }

        if seconds.is_sign_positive() {
            self.checked_add(Duration::from_secs_f64(seconds))
        } else {
            self.checked_sub(Duration::from_secs_f64(-seconds))
        }
    }
}
```

See: https://github.com/artichoke/artichoke/issues/2194.

`@rustbot` label +T-libs-api -T-libs

cc `@mbartlett21`
2022-10-24 19:32:26 +09:00
..
benches add a benchmark for slice_iter.copied().array_chunks() 2022-10-17 23:40:21 +02:00
primitive_docs
src Rollup merge of #102271 - lopopolo:lopopolo/stabilize-duration-try-from-secs-float, r=dtolnay 2022-10-24 19:32:26 +09:00
tests Rollup merge of #102271 - lopopolo:lopopolo/stabilize-duration-try-from-secs-float, r=dtolnay 2022-10-24 19:32:26 +09:00
Cargo.toml