Show interior mutability chain in `mutable_key_type`
Fixes#10619
Just ran into this myself and I definitely agree it's not very nice to have to manually go through all the types involved to figure out why this happens and to evaluate if this is really a problem (knowing if the field of a struct is something that a hash impl relies on), so this changes the lint to emit notes for each step involved.
changelog: none
Restrict `ignore-mode-*` directives
This is only used by coverage test suites where the same sources get run under different coverage modes. Restrict `ignore-mode-<coverage_mode>` to only coverage modes.
coverage: Multiple small tweaks to counter creation
I've been experimenting with some larger changes to how coverage counters are assigned to parts of the control-flow graph, and while none of that is ready yet, along the way I've repeatedly found myself wanting these smaller tweaks as a base.
There are no changes to compiler output.
liballoc: introduce String, Vec const-slicing
This change `const`-qualifies many methods on `Vec` and `String`, notably `as_slice`, `as_str`, `len`. These changes are made behind the unstable feature flag `const_vec_string_slice`.
## Motivation
This is to support simultaneous variance over ownership and constness. I have an enum type that may contain either `String` or `&str`, and I want to produce a `&str` from it in a possibly-`const` context.
```rust
enum StrOrString<'s> {
Str(&'s str),
String(String),
}
impl<'s> StrOrString<'s> {
const fn as_str(&self) -> &str {
match self {
// In a const-context, I really only expect to see this variant, but I can't switch the implementation
// in some mode like #[cfg(const)] -- there has to be a single body
Self::Str(s) => s,
// so this is a problem, since it's not `const`
Self::String(s) => s.as_str(),
}
}
}
```
Currently `String` and `Vec` don't support this, but can without functional changes. Similar logic applies for `len`, `capacity`, `is_empty`.
## Changes
The essential thing enabling this change is that `Unique::as_ptr` is `const`. This lets us convert `RawVec::ptr` -> `Vec::as_ptr` -> `Vec::as_slice` -> `String::as_str`.
I had to move the `Deref` implementations into `as_{str,slice}` because `Deref` isn't `#[const_trait]`, but I would expect this change to be invisible up to inlining. I moved the `DerefMut` implementations as well for uniformity.
Don't use Immediate::offset to transmute pointers to integers
This applies the relatively new `assert_matches_abi` check in the `offset` operation on immediates, which makes sure that if offsets are used to alter the layout (which is possible because the field layout is arbitrarily picked by the caller), this is not done in a way that breaks the invariant of the `Immediate` type.
This leads to ICEs in a GVN mir-opt test, so the second commit fixes GVN.
Fixes https://github.com/rust-lang/rust/issues/131064.
This change `const`-qualifies many methods on Vec and String, notably
`as_slice`, `as_str`, `len`. These changes are made behind the unstable
feature flag `const_vec_string_slice` with the following tracking issue:
https://github.com/rust-lang/rust/issues/129041
