Introduce `as_deref` to Option
This is re-submission for #59628.
Renames `deref()` to `as_deref()` and adds `deref_mut()` impls and tests.
CC #50264
r? @Kimundi
(I picked you as you're the previous reviewer.)
Add key and value methods to DebugMap
Implementation PR for an active (not approved) RFC: https://github.com/rust-lang/rfcs/pull/2696.
Add two new methods to `std::fmt::DebugMap` for writing the key and value part of a map entry separately:
```rust
impl<'a, 'b: 'a> DebugMap<'a, 'b> {
pub fn key(&mut self, key: &dyn Debug) -> &mut Self;
pub fn value(&mut self, value: &dyn Debug) -> &mut Self;
}
```
I want to do this so that I can write a `serde::Serializer` that forwards to our format builders, so that any `T: Serialize` can also be treated like a `T: Debug`.
Implement nth_back for slice::{Iter, IterMut}
Part of #54054.
I implemented `nth_back` as straightforwardly as I could, and then slightly changed `nth` to match `nth_back`. I believe I did so correctly, but please double-check 🙂
I also added the helper methods `zst_shrink`, `next_unchecked`, and `next_back_unchecked` to get rid of some duplicated code. These changes hopefully make this code easier to understand for new contributors like me.
I noticed the `is_empty!` and `len!` macros which sole purpose seems to be inlining, according to the comment right above them, but the `is_empty` and `len` methods are already marked with `#[inline(always)]`. Does that mean we could replace these macros with method calls, without affecting anything? I'd love to get rid of them.
Implement nth_back for RChunks(Exact)(Mut)
Part of #54054.
These implementations may not be optimal because of the use of `self.len()`, but it's quite cheap and simplifies the code a lot.
There's quite some duplication going on here, I wouldn't mind cleaning this up later. A good next step would probably be to add private `split_off_up_to`/`split_off_from` helper methods for slices since their behavior is commonly useful throughout the `Chunks` types.
r? @scottmcm
Implement `iter::Sum` and `iter::Product` for `Option`
This is similar to the existing implementation for `Result`. It will take each item into the accumulator unless a `None` is returned.
I based a lot of this on #38580. From that discussion it didn't seem like this addition would be too controversial or difficult. One thing I still don't understand is picking the values for the `stable` attribute. This is my first non-documentation PR for rust so I am open to any feedback on improvements.
coretest: Downgrade deny to warn
The `deny` causes a build failure in https://github.com/RalfJung/miri-test-libstd. Since we use `-D warnings` for rustc builds, `warn` should be enough to lead to compile errors here, without impeding external builds.
Implement saturating_abs() and saturating_neg() functions for signed integer types
Similar to wrapping_abs() / wrapping_neg() functions but saturating at the numeric bounds instead of wrapping around. Complements the existing set of functions with saturation mechanics.
cc #59983
