bjoernager/rust
bjoernager/rust
1
Fork 0
Code Activity

Auto merge of #80962 - jhpratt:const_int_fn-stabilization, r=dtolnay

Browse source 
Stabilize remaining integer methods as `const fn`

This pull request stabilizes the following methods as `const fn`:

- `i*::checked_div`
- `i*::checked_div_euclid`
- `i*::checked_rem`
- `i*::checked_rem_euclid`
- `i*::div_euclid`
- `i*::overflowing_div`
- `i*::overflowing_div_euclid`
- `i*::overflowing_rem`
- `i*::overflowing_rem_euclid`
- `i*::rem_euclid`
- `i*::wrapping_div`
- `i*::wrapping_div_euclid`
- `i*::wrapping_rem`
- `i*::wrapping_rem_euclid`
- `u*::checked_div`
- `u*::checked_div_euclid`
- `u*::checked_rem`
- `u*::checked_rem_euclid`
- `u*::div_euclid`
- `u*::overflowing_div`
- `u*::overflowing_div_euclid`
- `u*::overflowing_rem`
- `u*::overflowing_rem_euclid`
- `u*::rem_euclid`
- `u*::wrapping_div`
- `u*::wrapping_div_euclid`
- `u*::wrapping_rem`
- `u*::wrapping_rem_euclid`

These can all be implemented on the current stable (1.49). There are two unstable details: const likely/unlikely and unchecked division/remainder. Both of these are for optimizations, and are in no way required to make the methods function; there is no exposure of these details publicly. Per comments below, it seems best practice is to stabilize the intrinsics. As such, `intrinsics::unchecked_div` and `intrinsics::unchecked_rem` have been stabilized as `const` as part of this pull request as well. The methods themselves remain unstable.

I believe part of the reason these were not stabilized previously was the behavior around division by 0 and modulo 0. After testing on nightly, the diagnostic for something like `const _: i8 = 5i8 % 0i8;` is similar to that of `const _: i8 = 5i8.rem_euclid(0i8);` (assuming the appropriate feature flag is enabled). As such, I believe these methods are ready to be stabilized as `const fn`.

This pull request represents the final methods mentioned in #53718. As such, this PR closes #53718.

`@rustbot` modify labels to +A-const-fn, +T-libs
This commit is contained in:
bors 2021-02-08 05:05:55 +00:00
commit 4940dd483a
5 changed files with 30 additions and 38 deletions
Download patch file Download diff file Expand all files Collapse all files

3
library/core/src/lib.rs
View file

@ -73,11 +73,8 @@
#![feature(const_discriminant)]
#![feature(const_cell_into_inner)]
#![feature(const_intrinsic_copy)]
#![feature(const_checked_int_methods)]
#![feature(const_euclidean_int_methods)]
#![feature(const_float_classify)]
#![feature(const_float_bits_conv)]
#![feature(const_overflowing_int_methods)]
#![feature(const_int_unchecked_arith)]
#![feature(const_mut_refs)]
#![feature(const_cttz)]