Exploiting the fact that getting the length of the slices is known, we
can use a counted loop instead of iterators, which means that we only
need a single counter, instead of having to increment and check one
pointer for each iterator.
Benchmarks comparing vectors with 100,000 elements:
Before:
```
running 8 tests
test eq1_u8 ... bench: 66,757 ns/iter (+/- 113)
test eq2_u16 ... bench: 111,267 ns/iter (+/- 149)
test eq3_u32 ... bench: 126,282 ns/iter (+/- 111)
test eq4_u64 ... bench: 126,418 ns/iter (+/- 155)
test ne1_u8 ... bench: 88,990 ns/iter (+/- 161)
test ne2_u16 ... bench: 89,126 ns/iter (+/- 265)
test ne3_u32 ... bench: 96,901 ns/iter (+/- 92)
test ne4_u64 ... bench: 96,750 ns/iter (+/- 137)
```
After:
```
running 8 tests
test eq1_u8 ... bench: 46,413 ns/iter (+/- 521)
test eq2_u16 ... bench: 46,500 ns/iter (+/- 74)
test eq3_u32 ... bench: 50,059 ns/iter (+/- 92)
test eq4_u64 ... bench: 54,001 ns/iter (+/- 92)
test ne1_u8 ... bench: 47,595 ns/iter (+/- 53)
test ne2_u16 ... bench: 47,521 ns/iter (+/- 59)
test ne3_u32 ... bench: 44,889 ns/iter (+/- 74)
test ne4_u64 ... bench: 47,775 ns/iter (+/- 68)
```
Fixes#24249
I've tagged all items that were missing docs to allow them to compile for now, the ones in core/num should probably be documented at least.
This is also a breaking change for any crates using `#[deny(missing_docs)]` that have undocumented constants, not sure there is any way to avoid this without making it a separate lint?
`MethodCallee` now has no information about the method, other than its `DefId`.
The previous bits of information can be recovered as follows:
```rust
let method_item = tcx.impl_or_trait_item(callee.def_id);
let container = method_item.container();
```
The method is inherent if `container` is a `ty::ImplContainer`:
* the `impl` the method comes from is `container.id()`
The method is a trait method if `container` is a `ty::TraitContainer:
* the `trait` the method is part of is `container.id()`
* a `ty::TraitRef` can be constructed by putting together:
* `container.id()` as the `trait` ID
* `callee.substs.clone().method_to_trait()` as the `trait` substs (including `Self`)
* the above `trait_ref` is a valid `T: Trait<A, B, C>` predicate
* selecting `trait_ref` could result in one of the following:
* `traits::VtableImpl(data)`: static dispatch to `data.impl_def_id`
* `traits::VtableObject(data)`: dynamic dispatch, with the vtable index:
`traits::get_vtable_index_of_object_method(tcx, data, callee.def_id)`
* other variants of `traits::Vtable`: various other `impl` sources
core: Use memcmp in is_prefix_of / is_suffix_of
The basic str equality in core::str calls memcmp, re-use the same
function in StrSearcher's is_prefix_of, is_suffix_of.
Documentation claims it panics on out of bounds -- it regards out of
bounds as just not a char boundary.
core::str module is aware of how it works and uses it appropriately.
Maybe we should rename it to `is_valid_index`, `is_slicable_index`, or
something similar.
