Constier maybe uninit
I was playing around trying to make `[T; N]::zip()` in #79451 be `const fn`. One of the things I bumped into was `MaybeUninit::assume_init`. Is there any reason for the intrinsic `assert_inhabited<T>()` and therefore `MaybeUninit::assume_init` not being `const`?
---
I have as best as I could tried to follow the instruction in [library/core/src/intrinsics.rs](https://github.com/rust-lang/rust/blob/master/library/core/src/intrinsics.rs#L11). I have no idea what I am doing but it seems to compile after some slight changes after the copy paste. Is this anywhere near how this should be done?
Also any ideas for name of the feature gate? I guess `const_maybe_assume_init` is quite misleading since I have added some more methods. Should I add test? If so what should be tested?
remove this weird special case from promotion
Promotion has a special case to ignore interior mutability under some specific circumstances. The purpose of this PR is to figure out what changes if we remove that. Since `Cell::new` and friends only get promoted inside `const`/`static` initializers these days, it actually is not easy to exploit this case: you need something like
```rust
const TEST_INTERIOR_MUT: () = {
// The "0." case is already ruled out by not permitting any interior mutability in `const`.
let _val: &'static _ = &(Cell::new(1), 2).1;
};
```
I assume something like `&Some(&(Cell::new(1), 2).1)` would hit the nested case inside `validate_rvalue`... though I am not sure why that would not just trigger nested promotion, first promoting the inner reference and then the outer one?
Fixes https://github.com/rust-lang/rust/issues/67534 (by simply rejecting that code^^)
r? `@oli-obk` (but for now this is not meant to be merged!)
Cc `@rust-lang/wg-const-eval`
Validate naked functions definitions
Validate that naked functions are defined in terms of a single inline assembly
block that uses only `const` and `sym` operands and has `noreturn` option.
Implemented as future incompatibility lint with intention to migrate it into
hard error. When it becomes a hard error it will ensure that naked functions are
either unsafe or contain an unsafe block around the inline assembly. It will
guarantee that naked functions do not reference functions parameters (obsoleting
part of existing checks from #79411). It will limit the definitions of naked
functions to what can be reliably supported. It will also reject naked functions
implemented using legacy LLVM style assembly since it cannot satisfy those
conditions.
https://github.com/rust-lang/rfcs/pull/2774https://github.com/rust-lang/rfcs/pull/2972
Const parameters can not be inferred with `_` help note
This should close: #79557
# Example output
```
error[E0747]: type provided when a constant was expected
--> inferred_const_note.rs:6:19
|
6 | let a = foo::<_, 2>([0, 1, 2]);
| ^
|
= help: Const parameters can not be inferred with `_`
error: aborting due to previous error
For more information about this error, try `rustc --explain E0747`.
```
r? `@lcnr`
A slightly clearer diagnostic when misusing const
Fixes#79598
This produces the following diagnostic:
"expected one of `>`, a const expression, lifetime, or type, found keyword `const`"
Instead of the previous, more confusing:
"expected one of `>`, const, lifetime, or type, found keyword `const`"
This might not be completely clear as some users might not understand what a const expression is, but I do believe this is an improvement.
Fix src/test/ui/env-vars.rs on 128-core machines on Windows
On Windows, the environment variable NUMBER_OF_PROCESSORS has special
meaning. Unfortunately, you can get different answers, depending on
whether you are enumerating all environment variables or querying a
specific variable. This was causing the src/test/ui/env-vars.rs test
to fail on machines with more than 64 processors when run on Windows.
check the recursion limit when finding a struct's tail
fixes#79437
This does a `delay_span_bug` (via `ty_error_with_message`) rather than emit a new error message, under the assumption that there will be an error elsewhere (even if the type isn't infinitely recursive, just deeper than the recursion limit, this appears to be the case).
On Windows, the environment variable NUMBER_OF_PROCESSORS has special
meaning. Unfortunately, you can get different answers, depending on
whether you are enumerating all environment variables or querying a
specific variable. This was causing the src/test/ui/env-vars.rs test
to fail on machines with more than 64 processors when run on Windows.
Revert "Auto merge of #79209
r? `@nikomatsakis`
This has caused some issues (#79560) so better to revert and try to come up with a proper fix without rush.
Do not show negative polarity trait implementations in diagnostic messages for similar implementations
This fixes#79458.
Previously, this code:
```rust
#[derive(Clone)]
struct Foo<'a, T> {
x: &'a mut T,
}
```
would have suggested that `<&mut T as Clone>` was an implementation that was found. This is due to the fact that the standard library now has `impl<'_, T> !Clone for &'_ mut T`, and explicit negative polarity implementations were not filtered out in diagnostic output when suggesting similar implementations.
This PR fixes this issue by filtering out negative polarity trait implementations in `find_similar_impl_candidates` within `rustc_trait_selection::traits::error_reporting::InferCtxtPrivExt<'tcx>`. It also adds a UI regression test for this issue and fixes UI tests that had incorrectly been modified to expect the invalid output.
r? `@scottmcm`
Use true previous lint level when detecting overriden forbids
Previously, cap-lints was ignored when checking the previous forbid level, which
meant that it was a hard error to do so. This is different from the normal
behavior of lints, which are silenced by cap-lints; if the forbid would not take
effect regardless, there is not much point in complaining about the fact that we
are reducing its level.
It might be considered a bug that even `--cap-lints deny` would suffice to
silence the error on overriding forbid, depending on if one cares about failing
the build or precisely forbid being set. But setting cap-lints to deny is quite
odd and not really done in practice, so we don't try to handle it specially.
This also unifies the code paths for nested and same-level scopes. However, the
special case for CLI lint flags is left in place (introduced by #70918) to fix
the regression noted in #70819. That means that CLI flags do not lint on forbid
being overridden by a non-forbid level. It is unclear whether this is a bug or a
desirable feature, but it is certainly inconsistent. CLI flags are a
sufficiently different "type" of place though that this is deemed out of scope
for this commit.
r? `@pnkfelix` perhaps?
cc #77713 -- not marking as "Fixes" because of the lack of proper unused attribute handling in this PR
