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- [x] Removed `?const` and change uses of `?const`
- [x] Added `~const` to the AST. It is gated behind const_trait_impl.
- [x] Validate `~const` in ast_validation.
- [ ] Add enum `BoundConstness` to the HIR. (With variants `NotConst` and
`ConstIfConst` allowing future extensions)
- [ ] Adjust trait selection and pre-existing code to use `BoundConstness`.
- [ ] Optional steps (*for this PR, obviously*)
- [ ] Fix #88155
- [ ] Do something with constness bounds in chalk
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Instead of updating global state to mark attributes as used,
we now explicitly emit a warning when an attribute is used in
an unsupported position. As a side effect, we are to emit more
detailed warning messages (instead of just a generic "unused" message).
`Session.check_name` is removed, since its only purpose was to mark
the attribute as used. All of the callers are modified to use
`Attribute.has_name`
Additionally, `AttributeType::AssumedUsed` is removed - an 'assumed
used' attribute is implemented by simply not performing any checks
in `CheckAttrVisitor` for a particular attribute.
We no longer emit unused attribute warnings for the `#[rustc_dummy]`
attribute - it's an internal attribute used for tests, so it doesn't
mark sense to treat it as 'unused'.
With this commit, a large source of global untracked state is removed.
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Stabilize `arbitrary_enum_discriminant`
Closes #60553.
----
## Stabilization Report
_copied from https://github.com/rust-lang/rust/issues/60553#issuecomment-865922311_
### Summary
Enables a user to specify *explicit* discriminants on arbitrary enums.
Previously, this was hard to achieve:
```rust
#[repr(u8)]
enum Foo {
A(u8) = 0,
B(i8) = 1,
C(bool) = 42,
}
```
Someone would need to add 41 hidden variants in between as a workaround with implicit discriminants.
In conjunction with [RFC 2195](https://github.com/rust-lang/rfcs/blob/master/text/2195-really-tagged-unions.md), this feature would provide more flexibility for FFI and unsafe code involving enums.
### Test cases
Most tests are in [`src/test/ui/enum-discriminant`](https://github.com/rust-lang/rust/tree/master/src/test/ui/enum-discriminant), there are two [historical](https://github.com/rust-lang/rust/blob/master/src/test/ui/parser/tag-variant-disr-non-nullary.rs) [tests](https://github.com/rust-lang/rust/blob/master/src/test/ui/parser/issue-17383.rs) that are now covered by the feature (removed by this pr due to them being obsolete).
### Edge cases
The feature is well defined and does not have many edge cases.
One [edge case](https://github.com/rust-lang/rust/issues/70509) was related to another unstable feature named `repr128` and is resolved.
### Previous PRs
The [implementation PR](https://github.com/rust-lang/rust/pull/60732) added documentation to the Unstable Book, https://github.com/rust-lang/reference/pull/1055 was opened as a continuation of https://github.com/rust-lang/reference/pull/639.
### Resolution of unresolved questions
The questions are resolved in https://github.com/rust-lang/rust/issues/60553#issuecomment-511235271.
----
(someone please add `needs-fcp`)
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Remove min_type_alias_impl_trait in favor of type_alias_impl_trait
r? ``@oli-obk``
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Stabilize bindings_after_at
attempting to stabilze bindings_after_at [#65490](https://github.com/rust-lang/rust/issues/65490), im pretty new to the whole thing so any pointers are greatly appreciated.
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Stabilize "RangeFrom" patterns in 1.55
Implements a partial stabilization of #67264 and #37854.
Reference PR: https://github.com/rust-lang/reference/pull/900
# Stabilization Report
This stabilizes the `X..` pattern, shown as such, offering an exhaustive match for unsigned integers:
```rust
match x as u32 {
0 => println!("zero!"),
1.. => println!("positive number!"),
}
```
Currently if a Rust author wants to write such a match on an integer, they must use `1..={integer}::MAX` . By allowing a "RangeFrom" style pattern, this simplifies the match to not require the MAX path and thus not require specifically repeating the type inside the match, allowing for easier refactoring. This is particularly useful for instances like the above case, where different behavior on "0" vs. "1 or any positive number" is desired, and the actual MAX is unimportant.
Notably, this excepts slice patterns which include half-open ranges from stabilization, as the wisdom of those is still subject to some debate.
## Practical Applications
Instances of this specific usage have appeared in the compiler:
https://github.com/rust-lang/rust/blob/16143d10679537d3fde4247e15334e78ad9d55b9/compiler/rustc_middle/src/ty/inhabitedness/mod.rs#L219
https://github.com/rust-lang/rust/blob/673d0db5e393e9c64897005b470bfeb6d5aec61b/compiler/rustc_ty_utils/src/ty.rs#L524
And I have noticed there are also a handful of "in the wild" users who have deployed it to similar effect, especially in the case of rejecting any value of a certain number or greater. It simply makes it much more ergonomic to write an irrefutable match, as done in Katholieke Universiteit Leuven's [SCALE and MAMBA project](https://github.com/KULeuven-COSIC/SCALE-MAMBA/blob/05e5db00d553573534258585651c525d0da5f83f/WebAssembly/scale_std/src/fixed_point.rs#L685-L695).
## Tests
There were already many tests in [src/test/ui/half-open-range/patterns](https://github.com/rust-lang/rust/tree/90a2e5e3fe59a254d4d707aa291517b3791ea5a6/src/test/ui/half-open-range-patterns), as well as [generic pattern tests that test the `exclusive_range_pattern` feature](https://github.com/rust-lang/rust/blob/673d0db5e393e9c64897005b470bfeb6d5aec61b/src/test/ui/pattern/usefulness/integer-ranges/reachability.rs), many dating back to the feature's introduction and remaining standing to this day. However, this stabilization comes with some additional tests to explore the... sometimes interesting behavior of interactions with other patterns. e.g. There is, at least, a mild diagnostic improvement in some edge cases, because before now, the pattern `0..=(5+1)` encounters the `half_open_range_patterns` feature gate and can thus emit the request to enable the feature flag, while also emitting the "inclusive range with no end" diagnostic. There is no intent to allow an `X..=` pattern that I am aware of, so removing the flag request is a strict improvement. The arrival of the `J | K` "or" pattern also enables some odd formations.
Some of the behavior tested for here is derived from experiments in this [Playground](https://play.rust-lang.org/?version=nightly&mode=debug&edition=2018&gist=58777b3c715c85165ac4a70d93efeefc) example, linked at https://github.com/rust-lang/rust/issues/67264#issuecomment-812770692, which may be useful to reference to observe the current behavior more closely.
In addition tests constituting an explanation of the "slicing range patterns" syntax issue are included in this PR.
## Desiderata
The exclusive range patterns and half-open range patterns are fairly strongly requested by many authors, as they make some patterns much more natural to write, but there is disagreement regarding the "closed" exclusive range pattern or the "RangeTo" pattern, especially where it creates "off by one" gaps in the presence of a "catch-all" wildcard case. Also, there are obviously no range analyses in place that will force diagnostics for e.g. highly overlapping matches. I believe these should be warned on, ideally, and I think it would be reasonable to consider such a blocker to stabilizing this feature, but there is no technical issue with the feature as-is from the purely syntactic perspective as such overlapping or missed matches can already be generated today with such a catch-all case. And part of the "point" of the feature, at least from my view, is to make it easier to omit wildcard matches: a pattern with such an "open" match produces an irrefutable match and does not need the wild card case, making it easier to benefit from exhaustiveness checking.
## History
- Implemented:
- Partially via exclusive ranges: https://github.com/rust-lang/rust/pull/35712
- Fully with half-open ranges: https://github.com/rust-lang/rust/pull/67258
- Unresolved Questions:
- The precedence concerns of https://github.com/rust-lang/rust/pull/48501 were considered as likely requiring adjustment but probably wanting a uniform consistent change across all pattern styles, given https://github.com/rust-lang/rust/issues/67264#issuecomment-720711656, but it is still unknown what changes might be desired
- How we want to handle slice patterns in ranges seems to be an open question still, as witnessed in the discussion of this PR!
I checked but I couldn't actually find an RFC for this, and given "approved provisionally by lang team without an RFC", I believe this might require an RFC before it can land? Unsure of procedure here, on account of this being stabilizing a subset of a feature of syntax.
r? `@scottmcm`
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Handle C-variadic arguments properly when reporting region errors
This pull request fixes #86053. The issue is that for a C-variadic function
```rust
#![feature(c_variadic)]
unsafe extern "C" fn foo(_: (), ...) {}
```
`foo`'s signature will contain only the first parameter (and have `c_variadic` set to `true`), whereas its body has a second argument (a `hir::Pat` for the `...`).
The code for reporting region errors iterates over the body's parameters and tries to fetch the corresponding parameter from the signature; this causes an out-of-bounds ICE for the `...` (though not in the example above, because there are no region errors to report).
I have simply restricted the iteration over the body parameters to exclude `...`, which is fine because `...` cannot cause a region error.
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Fix some diagnostic issues with const_generics_defaults feature gate
This PR makes a few changes:
- print out const param defaults in "lifetime ordering" errors rather than discarding them
- update `is_simple_text` to account for const params when checking if a type has no generics, this was causing a note to be failed to add to an error message
- fixes some diagnostic wording that incorrectly said there was ordering restrictions between type/const params despite the `const_generics_defaults` feature gate is active
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position.
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# Stabilization report
## Summary
This stabilizes using macro expansion in key-value attributes, like so:
```rust
#[doc = include_str!("my_doc.md")]
struct S;
#[path = concat!(env!("OUT_DIR"), "/generated.rs")]
mod m;
```
See the changes to the reference for details on what macros are allowed;
see Petrochenkov's excellent blog post [on internals](https://internals.rust-lang.org/t/macro-expansion-points-in-attributes/11455)
for alternatives that were considered and rejected ("why accept no more
and no less?")
This has been available on nightly since 1.50 with no major issues.
## Notes
### Accepted syntax
The parser accepts arbitrary Rust expressions in this position, but any expression other than a macro invocation will ultimately lead to an error because it is not expected by the built-in expression forms (e.g., `#[doc]`). Note that decorators and the like may be able to observe other expression forms.
### Expansion ordering
Expansion of macro expressions in "inert" attributes occurs after decorators have executed, analogously to macro expressions appearing in the function body or other parts of decorator input.
There is currently no way for decorators to accept macros in key-value position if macro expansion must be performed before the decorator executes (if the macro can simply be copied into the output for later expansion, that can work).
## Test cases
- https://github.com/rust-lang/rust/blob/master/src/test/ui/attributes/key-value-expansion-on-mac.rs
- https://github.com/rust-lang/rust/blob/master/src/test/rustdoc/external-doc.rs
The feature has also been dogfooded extensively in the compiler and
standard library:
- https://github.com/rust-lang/rust/pull/83329
- https://github.com/rust-lang/rust/pull/83230
- https://github.com/rust-lang/rust/pull/82641
- https://github.com/rust-lang/rust/pull/80534
## Implementation history
- Initial proposal: https://github.com/rust-lang/rust/issues/55414#issuecomment-554005412
- Experiment to see how much code it would break: https://github.com/rust-lang/rust/pull/67121
- Preliminary work to restrict expansion that would conflict with this
feature: https://github.com/rust-lang/rust/pull/77271
- Initial implementation: https://github.com/rust-lang/rust/pull/78837
- Fix for an ICE: https://github.com/rust-lang/rust/pull/80563
## Unresolved Questions
~~https://github.com/rust-lang/rust/pull/83366#issuecomment-805180738 listed some concerns, but they have been resolved as of this final report.~~
## Additional Information
There are two workarounds that have a similar effect for `#[doc]`
attributes on nightly. One is to emulate this behavior by using a limited version of this feature that was stabilized for historical reasons:
```rust
macro_rules! forward_inner_docs {
($e:expr => $i:item) => {
#[doc = $e]
$i
};
}
forward_inner_docs!(include_str!("lib.rs") => struct S {});
```
This also works for other attributes (like `#[path = concat!(...)]`).
The other is to use `doc(include)`:
```rust
#![feature(external_doc)]
#[doc(include = "lib.rs")]
struct S {}
```
The first works, but is non-trivial for people to discover, and
difficult to read and maintain. The second is a strange special-case for
a particular use of the macro. This generalizes it to work for any use
case, not just including files.
I plan to remove `doc(include)` when this is stabilized. The
`forward_inner_docs` workaround will still compile without warnings, but
I expect it to be used less once it's no longer necessary.
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Add unnamed_fields feature gate and gate unnamed fields on parsing
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This commit implements both the native linking modifiers infrastructure
as well as an initial attempt at the individual modifiers from the RFC.
It also introduces a feature flag for the general syntax along with
individual feature flags for each modifier.
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Revert "Rollup merge of #82296 - spastorino:pubrules, r=nikomatsakis"
This reverts commit e2561c58a41023a14e0e583113dcf55e1ecb236a, reversing
changes made to 2982ba50fc4bb629b8fe4108a81cb2f9b053510b.
As discussed in #83641 this feature is not complete and in particular doesn't work cross macros and given that this is not going to be included in edition 2021 nobody seems to be trying to fix the underlying problem. When can add this again I guess, whenever somebody has the time to make it work cross crates.
r? `@nikomatsakis`
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Always reject `const fn` in `trait` during parsing.
'const fn' in trait are rejected in the AST:
https://github.com/rust-lang/rust/blob/b78c0d8a4d5af91a4a55d029293e3ecb879ec142/compiler/rustc_ast_passes/src/ast_validation.rs#L1411
So this feature gate check is a NOP and we can just remove it.
The src/test/ui/feature-gates/feature-gate-min_const_fn.rs and src/test/ui/feature-gates/feature-gate-const_fn.rs tests ensure that we still reject `const fn` in `trait`
Cc https://github.com/rust-lang/rust/issues/84510
r? `@oli-obk`
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various const parameter defaults improvements
Actually resolve names in const parameter defaults, fixing `struct Foo<const N: usize = { usize::MAX }>`.
---
Split generic parameter ban rib for types and consts, allowing
```rust
#![feature(const_generics_defaults)]
struct Q;
struct Foo<T = Q, const Q: usize = 3>(T);
```
---
Remove the type/const ordering restriction if `const_generics_defaults` is active, even if `const_generics` is not. allowing us to stabilize and test const param defaults separately.
---
Check well formedness of const parameter defaults, eagerly emitting an error for `struct Foo<const N: usize = { 0 - 1 }>`
---
Do not forbid const parameters in param defaults, allowing `struct Foo<const N: usize, T = [u8; N]>(T)` and `struct Foo<const N: usize, const M: usize = N>`. Note that this should not change anything which is stabilized, as on stable, type parameters must be in front of const parameters, which means that type parameter defaults are only allowed if no const parameters exist.
We still forbid generic parameters inside of const param types.
r? `@varkor` `@petrochenkov`
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On stable, suggest removing `#![feature]` for features that have been stabilized
I don't know how to test this (https://rust-lang.zulipchat.com/#narrow/stream/182449-t-compiler.2Fhelp/topic/Run.20tests.20without.20enabling.20nightly.20features.3F). I confirmed locally that this gives the
appropriate help with `channel = "beta"`:
```
error[E0554]: `#![feature]` may not be used on the beta release channel
--> src/lib.rs:2:1
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2 | #![feature(min_const_generics)]
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: remove the attribute
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= help: the feature `min_const_generics` has been stable since 1.51.0 and no longer requires an attribute to enable
error[E0554]: `#![feature]` may not be used on the beta release channel
--> src/lib.rs:3:1
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3 | #![feature(min_const_generics, min_specialization)]
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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= help: the feature `min_const_generics` has been stable since 1.51.0 and no longer requires an attribute to enable
error[E0554]: `#![feature]` may not be used on the beta release channel
--> src/lib.rs:4:1
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4 | #![feature(box_patterns)]
| ^^^^^^^^^^^^^^^^^^^^^^^^^
```
Closes https://github.com/rust-lang/rust/issues/83715.
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This reverts commit e2561c58a41023a14e0e583113dcf55e1ecb236a, reversing
changes made to 2982ba50fc4bb629b8fe4108a81cb2f9b053510b.
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Stablize `non-ascii-idents`
This is the stablization PR for RFC 2457. Currently this is waiting on fcp in [tracking issue](https://github.com/rust-lang/rust/issues/55467).
r? `@Manishearth`
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This commit implements the idea of a new ABI for the WebAssembly target,
one called `"wasm"`. This ABI is entirely of my own invention
and has no current precedent, but I think that the addition of this ABI
might help solve a number of issues with the WebAssembly targets.
When `wasm32-unknown-unknown` was first added to Rust I naively
"implemented an abi" for the target. I then went to write `wasm-bindgen`
which accidentally relied on details of this ABI. Turns out the ABI
definition didn't match C, which is causing issues for C/Rust interop.
Currently the compiler has a "wasm32 bindgen compat" ABI which is the
original implementation I added, and it's purely there for, well,
`wasm-bindgen`.
Another issue with the WebAssembly target is that it's not clear to me
when and if the default C ABI will change to account for WebAssembly's
multi-value feature (a feature that allows functions to return multiple
values). Even if this does happen, though, it seems like the C ABI will
be guided based on the performance of WebAssembly code and will likely
not match even what the current wasm-bindgen-compat ABI is today. This
leaves a hole in Rust's expressivity in binding WebAssembly where given
a particular import type, Rust may not be able to import that signature
with an updated C ABI for multi-value.
To fix these issues I had the idea of a new ABI for WebAssembly, one
called `wasm`. The definition of this ABI is "what you write
maps straight to wasm". The goal here is that whatever you write down in
the parameter list or in the return values goes straight into the
function's signature in the WebAssembly file. This special ABI is for
intentionally matching the ABI of an imported function from the
environment or exporting a function with the right signature.
With the addition of a new ABI, this enables rustc to:
* Eventually remove the "wasm-bindgen compat hack". Once this
ABI is stable wasm-bindgen can switch to using it everywhere.
Afterwards the wasm32-unknown-unknown target can have its default ABI
updated to match C.
* Expose the ability to precisely match an ABI signature for a
WebAssembly function, regardless of what the C ABI that clang chooses
turns out to be.
* Continue to evolve the definition of the default C ABI to match what
clang does on all targets, since the purpose of that ABI will be
explicitly matching C rather than generating particular function
imports/exports.
Naturally this is implemented as an unstable feature initially, but it
would be nice for this to get stabilized (if it works) in the near-ish
future to remove the wasm32-unknown-unknown incompatibility with the C
ABI. Doing this, however, requires the feature to be on stable because
wasm-bindgen works with stable Rust.
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I don't know how to test this. I confirmed locally that this gives the
appropriate help with `channel = "beta"`:
```
error[E0554]: `#![feature]` may not be used on the beta release channel
--> src/lib.rs:2:1
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2 | #![feature(min_const_generics)]
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: remove the attribute
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= help: the feature `min_const_generics` has been stable since 1.51.0 and no longer requires an attribute to enable
error[E0554]: `#![feature]` may not be used on the beta release channel
--> src/lib.rs:3:1
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3 | #![feature(min_const_generics, min_specialization)]
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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= help: the feature `min_const_generics` has been stable since 1.51.0 and no longer requires an attribute to enable
error[E0554]: `#![feature]` may not be used on the beta release channel
--> src/lib.rs:4:1
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4 | #![feature(box_patterns)]
| ^^^^^^^^^^^^^^^^^^^^^^^^^
```
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Rename `#[doc(spotlight)]` to `#[doc(notable_trait)]`
Fixes #80936.
"spotlight" is not a very specific or self-explaining name.
Additionally, the dialog that it triggers is called "Notable traits".
So, "notable trait" is a better name.
* Rename `#[doc(spotlight)]` to `#[doc(notable_trait)]`
* Rename `#![feature(doc_spotlight)]` to `#![feature(doc_notable_trait)]`
* Update documentation
* Improve documentation
r? `@Manishearth`
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This currently creates a field which is always false on GenericParamDefKind for future use when
consts are permitted to have defaults
Update const_generics:default locations
Previously just ignored them, now actually do something about them.
Fix using type check instead of value
Add parsing
This adds all the necessary changes to lower const-generics defaults from parsing.
Change P<Expr> to AnonConst
This matches the arguments passed to instantiations of const generics, and makes it specific to
just anonymous constants.
Attempt to fix lowering bugs
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StructField -> FieldDef ("field definition")
Field -> ExprField ("expression field", not "field expression")
FieldPat -> PatField ("pattern field", not "field pattern")
Also rename visiting and other methods working on them.
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"spotlight" is not a very specific or self-explaining name.
Additionally, the dialog that it triggers is called "Notable traits".
So, "notable trait" is a better name.
* Rename `#[doc(spotlight)]` to `#[doc(notable_trait)]`
* Rename `#![feature(doc_spotlight)]` to `#![feature(doc_notable_trait)]`
* Update documentation
* Improve documentation
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actual changes in behaviour
This makes `type_alias_impl_trait` not actually do anything anymore
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### Overview
This commit begins the implementation work for RFC 2945. For more
information, see the rendered RFC [1] and tracking issue [2].
A boolean `unwind` payload is added to the `C`, `System`, `Stdcall`,
and `Thiscall` variants, marking whether unwinding across FFI
boundaries is acceptable. The cases where each of these variants'
`unwind` member is true correspond with the `C-unwind`,
`system-unwind`, `stdcall-unwind`, and `thiscall-unwind` ABI strings
introduced in RFC 2945 [3].
### Feature Gate and Unstable Book
This commit adds a `c_unwind` feature gate for the new ABI strings.
Tests for this feature gate are included in `src/test/ui/c-unwind/`,
which ensure that this feature gate works correctly for each of the
new ABIs.
A new language features entry in the unstable book is added as well.
### Further Work To Be Done
This commit does not proceed to implement the new unwinding ABIs,
and is intentionally scoped specifically to *defining* the ABIs and
their feature flag.
### One Note on Test Churn
This will lead to some test churn, in re-blessing hash tests, as the
deleted comment in `src/librustc_target/spec/abi.rs` mentioned,
because we can no longer guarantee the ordering of the `Abi`
variants.
While this is a downside, this decision was made bearing in mind
that RFC 2945 states the following, in the "Other `unwind` Strings"
section [3]:
> More unwind variants of existing ABI strings may be introduced,
> with the same semantics, without an additional RFC.
Adding a new variant for each of these cases, rather than specifying
a payload for a given ABI, would quickly become untenable, and make
working with the `Abi` enum prone to mistakes.
This approach encodes the unwinding information *into* a given ABI,
to account for the future possibility of other `-unwind` ABI
strings.
### Ignore Directives
`ignore-*` directives are used in two of our `*-unwind` ABI test
cases.
Specifically, the `stdcall-unwind` and `thiscall-unwind` test cases
ignore architectures that do not support `stdcall` and
`thiscall`, respectively.
These directives are cribbed from
`src/test/ui/c-variadic/variadic-ffi-1.rs` for `stdcall`, and
`src/test/ui/extern/extern-thiscall.rs` for `thiscall`.
This would otherwise fail on some targets, see:
https://github.com/rust-lang-ci/rust/commit/fcf697f90206e9c87b39d494f94ab35d976bfc60
### Footnotes
[1]: https://github.com/rust-lang/rfcs/blob/master/text/2945-c-unwind-abi.md
[2]: https://github.com/rust-lang/rust/issues/74990
[3]: https://github.com/rust-lang/rfcs/blob/master/text/2945-c-unwind-abi.md#other-unwind-abi-strings
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