Minimize uses of `LocalInternedString`
`LocalInternedString` is described as "An alternative to `Symbol` and `InternedString`, useful when the chars within the symbol need to be accessed. It is best used for temporary values."
This PR makes the code match that comment, by removing all non-local uses of `LocalInternedString`. This allows the removal of a number of operations on `LocalInternedString` and a couple of uses of `unsafe`.
Make Allocation::bytes private
Fixes#62931.
Direct immutable access to the bytes is still possible but redirected through the new method `raw_bytes_with_undef_and_ptr`, similar to `get_bytes_with_undef_and_ptr` but without requiring an interpretation context and not doing *any* relocation or bounds checks. The `size` of the allocation is stored separately which makes access as `Size` and `usize` more ergonomic.
cc: @RalfJung
The old struct tail functions did not deal with `<T as Trait>::A` and `impl
Trait`, at least not explicitly. (We didn't notice this bug before because it
is only exposed when the tail (post deep normalization) is not `Sized`, so it
was a rare case to deal with.)
For post type-checking (i.e. during codegen), there is now
`struct_tail_erasing_lifetimes` and `struct_lockstep_tails_erasing_lifetimes`,
which each take an additional `ParamEnv` argument to drive normalization.
For pre type-checking cases where normalization is not needed, there is
`struct_tail_without_normalization`. (Currently, the only instance of this is
`Expectation::rvalue_hint`.)
All of these new entrypoints work by calling out to common helper routines.
The helpers are parameterized over a closure that handles the normalization.
Change visit api
r? @oli-obk
In the [first commit](37386d366a) of this PR, I'm changing `visit_place` to be the function that traverses the `Place` and have only that responsibility. Then there are two other functions `visit_place_base` and `visit_projection` which are the ones in charge of visiting the base and the projection. Visitor implementors can implement any of those.
In the [second commit](e786f631b8) we can already see some things that confuses me, which I think this division will make more clear. The old code, first checked if the place was a base, did something with it and then called `super_place` [here](e786f631b8 (diff-d583e4efe1a72516e274158e53223633L678)). `super_place` checks again if it's a base [here](https://github.com/rust-lang/rust/blob/master/src/librustc/mir/visit.rs#L679-L684) and in case is a local, visits the local and stuff like that. That's not very obvious on the code, and if I'm not wrong it's not needed. In this PR or we have [this](e786f631b8 (diff-d583e4efe1a72516e274158e53223633R673)) as I did or we can just do `- => self.super_place_base(...)` and that will be obvious that I'm letting the default implementation process the base.
* rename AllocKind -> GlobalAlloc. This stores the allocation itself, not just its kind.
* rename the methods that allocate stuff to have consistent names.
The commit should have changed comments as well.
At the time of writting, it passes the tidy and check tool.
Revisions asked by eddyb :
- Renamed of all the occurences of {visit/super}_mir
- Renamed test structures `CachedMir` to `Cached`
Fixing the missing import on `AggregateKind`
