This is consistent with all other diagnostics I could find containing
features and enables the use of `DiagSymbolList` for generalizing
diagnostics for unstable library features to multiple features.
The RFC for arbitrary self types v2 declares that we should reject
"generic" self types. This commit does so.
The definition of "generic" was unclear in the RFC, but has been
explored in
https://github.com/rust-lang/rust/issues/129147
and the conclusion is that "generic" means any `self` type which
is a type parameter defined on the method itself, or references
to such a type.
This approach was chosen because other definitions of "generic"
don't work. Specifically,
* we can't filter out generic type _arguments_, because that would
filter out Rc<Self> and all the other types of smart pointer
we want to support;
* we can't filter out all type params, because Self itself is a
type param, and because existing Rust code depends on other
type params declared on the type (as opposed to the method).
This PR decides to make a new error code for this case, instead of
reusing the existing E0307 error. This makes the code a
bit more complex, but it seems we have an opportunity to provide
specific diagnostics for this case so we should do so.
This PR filters out generic self types whether or not the
'arbitrary self types' feature is enabled. However, it's believed
that it can't have any effect on code which uses stable Rust, since
there are no stable traits which can be used to indicate a valid
generic receiver type, and thus it would have been impossible to
write code which could trigger this new error case.
It is however possible that this could break existing code which
uses either of the unstable `arbitrary_self_types` or
`receiver_trait` features. This breakage is intentional; as
we move arbitrary self types towards stabilization we don't want
to continue to support generic such types.
This PR adds lots of extra tests to arbitrary-self-from-method-substs.
Most of these are ways to trigger a "type mismatch" error which
9b82580c73/compiler/rustc_hir_typeck/src/method/confirm.rs (L519)
hopes can be minimized by filtering out generics in this way.
We remove a FIXME from confirm.rs suggesting that we make this change.
It's still possible to cause type mismatch errors, and a subsequent
PR may be able to improve diagnostics in this area, but it's harder
to cause these errors without contrived uses of the turbofish.
This is a part of the arbitrary self types v2 project,
https://github.com/rust-lang/rfcs/pull/3519https://github.com/rust-lang/rust/issues/44874
r? @wesleywiser
Retire the `unnamed_fields` feature for now
`#![feature(unnamed_fields)]` was implemented in part in #115131 and #115367, however work on that feature has (afaict) stalled and in the mean time there have been some concerns raised (e.g.[^1][^2]) about whether `unnamed_fields` is worthwhile to have in the language, especially in its current desugaring. Because it represents a compiler implementation burden including a new kind of anonymous ADT and additional complication to field selection, and is quite prone to bugs today, I'm choosing to remove the feature.
However, since I'm not one to really write a bunch of words, I'm specifically *not* going to de-RFC this feature. This PR essentially *rolls back* the state of this feature to "RFC accepted but not yet implemented"; however if anyone wants to formally unapprove the RFC from the t-lang side, then please be my guest. I'm just not totally willing to summarize the various language-facing reasons for why this feature is or is not worthwhile, since I'm coming from the compiler side mostly.
Fixes#117942Fixes#121161Fixes#121263Fixes#121299Fixes#121722Fixes#121799Fixes#126969Fixes#131041
Tracking:
* https://github.com/rust-lang/rust/issues/49804
[^1]: https://rust-lang.zulipchat.com/#narrow/stream/213817-t-lang/topic/Unnamed.20struct.2Funion.20fields
[^2]: https://github.com/rust-lang/rust/issues/49804#issuecomment-1972619108
Implement Return Type Notation (RTN)'s path form in where clauses
Implement return type notation (RTN) in path position for where clauses. We already had RTN in associated type position ([e.g.](https://play.rust-lang.org/?version=nightly&mode=debug&edition=2021&gist=627a4fb8e2cb334863fbd08ed3722c09)), but per [the RFC](https://rust-lang.github.io/rfcs/3654-return-type-notation.html#where-rtn-can-be-used-for-now):
> As a standalone type, RTN can only be used as the Self type of a where-clause [...]
Specifically, in order to enable code like:
```rust
trait Foo {
fn bar() -> impl Sized;
}
fn is_send(_: impl Send) {}
fn test<T>()
where
T: Foo,
T::bar(..): Send,
{
is_send(T::bar());
}
```
* In the resolver, when we see a `TyKind::Path` whose final segment is `GenericArgs::ParenthesizedElided` (i.e. `(..)`), resolve that path in the *value* namespace, since we're looking for a method.
* When lowering where clauses in HIR lowering, we first try to intercept an RTN self type via `lower_ty_maybe_return_type_notation`. If we find an RTN type, we lower it manually in a way that respects its higher-ranked-ness (see below) and resolves to the corresponding RPITIT. Anywhere else, we'll emit the same "return type notation not allowed in this position yet" error we do when writing RTN in every other position.
* In `resolve_bound_vars`, we add some special treatment for RTN types in where clauses. Specifically, we need to add new lifetime variables to our binders for the early- and late-bound vars we encounter on the method. This implements the higher-ranked desugaring [laid out in the RFC](https://rust-lang.github.io/rfcs/3654-return-type-notation.html#converting-to-higher-ranked-trait-bounds).
This PR also adds a bunch of tests, mostly negative ones (testing error messages).
In a follow-up PR, I'm going to mark RTN as no longer incomplete, since this PR basically finishes the impl surface that we should initially stabilize, and the RFC was accepted.
cc [RFC 3654](https://github.com/rust-lang/rfcs/pull/3654) and https://github.com/rust-lang/rust/issues/109417
Correct outdated object size limit
The comment here about 48 bit addresses being enough was written in 2016 but was made incorrect in 2019 by 5-level paging, and then persisted for another 5 years before being noticed and corrected.
The bolding of the "exclusive" part is merely to call attention to something I missed when reading it and doublechecking the math.
try-job: i686-msvc
try-job: test-various
Forbid borrows and unsized types from being used as the type of a const generic under `adt_const_params`
Fixes#112219Fixes#112124Fixes#112125
### Motivation
Currently the `adt_const_params` feature allows writing `Foo<const N: [u8]>` this is entirely useless as it is not possible to write an expression which evaluates to a type that is not `Sized`. In order to actually use unsized types in const generics they are typically written as `const N: &[u8]` which *is* possible to provide a value of.
Unfortunately allowing the types of const parameters to contain references is non trivial (#120961) as it introduces a number of difficult questions about how equality of references in the type system should behave. References in the types of const generics is largely only useful for using unsized types in const generics.
This PR introduces a new feature gate `unsized_const_parameters` and moves support for `const N: [u8]` and `const N: &...` from `adt_const_params` into it. The goal here hopefully is to experiment with allowing `const N: [u8]` to work without references and then eventually completely forbid references in const generics.
Splitting this out into a new feature gate means that stabilization of `adt_const_params` does not have to resolve#120961 which is the only remaining "big" blocker for the feature. Remaining issues after this are a few ICEs and naming bikeshed for `ConstParamTy`.
### Implementation
The implementation is slightly subtle here as we would like to ensure that a stabilization of `adt_const_params` is forwards compatible with any outcome of `unsized_const_parameters`. This is inherently tricky as we do not support unstable trait implementations and we determine whether a type is valid as the type of a const parameter via a trait bound.
There are a few constraints here:
- We would like to *allow for the possibility* of adding a `Sized` supertrait to `ConstParamTy` in the event that we wind up opting to not support unsized types and instead requiring people to write the 'sized version', e.g. `const N: [u8; M]` instead of `const N: [u8]`.
- Crates should be able to enable `unsized_const_parameters` and write trait implementations of `ConstParamTy` for `!Sized` types without downstream crates that only enable `adt_const_params` being able to observe this (required for std to be able to `impl<T> ConstParamTy for [T]`
Ultimately the way this is accomplished is via having two traits (sad), `ConstParamTy` and `UnsizedConstParamTy`. Depending on whether `unsized_const_parameters` is enabled or not we change which trait is used to check whether a type is allowed to be a const parameter.
Long term (when stabilizing `UnsizedConstParamTy`) it should be possible to completely merge these traits (and derive macros), only having a single `trait ConstParamTy` and `macro ConstParamTy`.
Under `adt_const_params` it is now illegal to directly refer to `ConstParamTy` it is only used as an internal impl detail by `derive(ConstParamTy)` and checking const parameters are well formed. This is necessary in order to ensure forwards compatibility with all possible future directions for `feature(unsized_const_parameters)`.
Generally the intuition here should be that `ConstParamTy` is the stable trait that everything uses, and `UnsizedConstParamTy` is that plus unstable implementations (well, I suppose `ConstParamTy` isn't stable yet :P).
Use structured suggestions for unconstrained generic parameters on impl blocks
I did not deduplicate with `UnusedGenericParameter`, because in contrast to type declarations, just using a generic parameter in an impl isn't enough, it must be used with the right variance and not just as part of a projection.
`C-cmse-nonsecure-call`: improved error messages
tracking issue: #81391
issue for the error messages (partially implemented by this PR): #81347
related, in that it also deals with CMSE: https://github.com/rust-lang/rust/pull/127766
When using the `C-cmse-nonsecure-call` ABI, both the arguments and return value must be passed via registers. Previously, when violating this constraint, an ugly LLVM error would be shown. Now, the rust compiler itself will print a pretty message and link to more information.
Rollup of 16 pull requests
Successful merges:
- #123374 (DOC: Add FFI example for slice::from_raw_parts())
- #124514 (Recommend to never display zero disambiguators when demangling v0 symbols)
- #125978 (Cleanup: HIR ty lowering: Consolidate the places that do assoc item probing & access checking)
- #125980 (Nvptx remove direct passmode)
- #126187 (For E0277 suggest adding `Result` return type for function when using QuestionMark `?` in the body.)
- #126210 (docs(core): make more const_ptr doctests assert instead of printing)
- #126249 (Simplify `[T; N]::try_map` signature)
- #126256 (Add {{target}} substitution to compiletest)
- #126263 (Make issue-122805.rs big endian compatible)
- #126281 (set_env: State the conclusion upfront)
- #126286 (Make `storage-live.rs` robust against rustc internal changes.)
- #126287 (Update a cranelift patch file for formatting changes.)
- #126301 (Use `tidy` to sort crate attributes for all compiler crates.)
- #126305 (Make PathBuf less Ok with adding UTF-16 then `into_string`)
- #126310 (Migrate run make prefer rlib)
- #126314 (fix RELEASES: we do not support upcasting to auto traits)
r? `@ghost`
`@rustbot` modify labels: rollup
Cleanup: Replace item names referencing GitHub issues or error codes with something more meaningful
**lcnr** in https://github.com/rust-lang/rust/pull/117164#pullrequestreview-1969935387:
> […] while I know that there's precendent to name things `Issue69420`, I really dislike this as it requires looking up the issue to figure out the purpose of such a variant. Actually referring to the underlying issue, e.g. `AliasMayNormToUncovered` or whatever and then linking to the issue in a doc comment feels a lot more desirable to me. We should ideally rename all the functions and enums which currently use issue numbers.
I've grepped through `compiler/` like crazy and think that I've found all instances of this pattern.
However, I haven't renamed `compute_2229_migrations_*`. Should I?
The first commit introduces an abhorrent and super long name for an item because naming is hard but also scary looking / unwelcoming names are good for things related to temporary-ish backcompat hacks. I'll let you discover it by yourself.
Contains a bit of drive-by cleanup and a diag migration bc that was the simplest option.
r? lcnr or compiler
