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.
This is an implementation of RFC rust-lang/rfcs#1156. It includes the code to implement the new rules, but that code is currently disabled. It also includes code to issue warnings when the change will cause breakage. These warnings try hard to be targeted but are also somewhat approximate. They could, with some effort, be made *more* targeted by adjusting the code in ty_relate that propagates the "will change" flag to consider the specific operation. Might be worth doing.
r? @pnkfelix (I think you understand region inference best)
