Use `Self` in docs when possible
Fixes#76542.
I used `rg '\s*//[!/]\s+fn [\w_]+\(&?self, ' .` in `library/` to find instances, I found some with that and some by manually checking.
@rustbot modify labels: C-enhancement T-doc
Avoid useless sift_down when std::collections::binary_heap::PeekMut is never mutably dereferenced
If `deref_mut` is never called then it's not possible for the element to be mutated without internal mutability, meaning there's no need to call `sift_down`.
This could be a little improvement in cases where you want to mutate the biggest element of the heap only if it satisfies a certain predicate that needs only read access to the element.
Move to intra-doc links in collections/vec_deque.rs and collections/vec_deque/drain.rs
Helps with #75080.
@rustbot modify labels: T-doc, A-intra-doc-links
Remove unused feature gates from library/ crates
Removes some unused feature gates from library crates. It's likely not a complete list as I only tested a subset for which it's more likely that it is unused.
Test and fix Send and Sync traits of BTreeMap artefacts
Fixes#76686.
I'm not quite sure what all this implies. E.g. comparing with the definitions for `NodeRef` in node.rs, maybe an extra bound `T: 'a` is useful for something. The test compiles on stable/beta (apart from `drain_filter`) so I bet `Sync` is equally desirable.
r? @Mark-Simulacrum
BTreeMap: wrap node's raw parent pointer in NonNull
Now that the other `*const` (root) is gone, seemed like a small step forward.
r? `@Mark-Simulacrum`
Add as_str() to string::Drain.
Vec's Drain recently [had its `.as_slice()` stabilized](https://github.com/rust-lang/rust/pull/72584), but String's Drain was still missing the analogous `.as_str()`. This adds that.
Also improves the Debug implementation, which now shows the remaining data instead of just `"Drain { .. }"`.
Add associated constant `BITS` to all integer types
Recently I've regularly come across this snippet (in a few different crates, including `core` and `std`):
```rust
std::mem::size_of<usize>() * 8
```
I think it's time for a `usize::BITS`.
BTreeMap: avoid slices even more
Epilogue to #73971: it seems the compiler is unable to realize that creating a slice and `get_unchecked`-ing one element is a simple fetch. So try to spell it out for the only remaining but often invoked case.
Also, the previous code doesn't seem fair game to me, using `get_unchecked` to reach beyond the end of a slice. Although the local function `slice_insert` also does that.
r? `@Mark-Simulacrum`
