Reorder trait bound modifiers *after* `for<...>` binder in trait bounds
This PR suggests changing the grammar of trait bounds from:
```
[CONSTNESS] [ASYNCNESS] [?] [BINDER] [TRAIT_PATH]
const async ? for<'a> Sized
```
to
```
([BINDER] [CONSTNESS] [ASYNCNESS] | [?]) [TRAIT_PATH]
```
i.e., either
```
? Sized
```
or
```
for<'a> const async Sized
```
(but not both)
### Why?
I think it's strange that the binder applies "more tightly" than the `?` trait polarity. This becomes even weirder when considering that we (or at least, I) want to have `async` trait bounds expressed like:
```
where T: for<'a> async Fn(&'a ()) -> i32,
```
and not:
```
where T: async for<'a> Fn(&'a ()) -> i32,
```
### Fallout
No crates on crater use this syntax, presumably because it's literally useless. This will require modifying the reference grammar, though.
### Alternatives
If this is not desirable, then we can alternatively keep parsing `for<'a>` after the `?` but deprecate it with either an FCW (or an immediate hard error), and begin parsing `for<'a>` *before* the `?`.
Deny keyword lifetimes pre-expansion
https://github.com/rust-lang/rust/pull/126452#issuecomment-2179464266
> Secondly, we confirmed that we're OK with moving the validation of keywords in lifetimes to pre-expansion from post-expansion. We similarly consider this a bug fix. While the breakage of the convenience feature of the with_locals crate that relies on this is unfortunate, and we wish we had not overlooked this earlier for that reason, we're fortunate that the breakage is contained to only one crate, and we're going to accept this breakage as the extra complexity we'd need to carry in the compiler to work around this isn't deemed worth it.
T-lang considers it to be a bugfix to deny `'keyword` lifetimes in the parser, rather than during AST validation that only happens post-expansion. This has one breakage: https://github.com/rust-lang/rust/pull/126452#issuecomment-2171654756
This probably should get lang FCP'd just for consistency.
Improve unsafe extern blocks diagnostics
Closes#126327
For this code:
```rust
extern {
pub fn foo();
pub safe fn bar();
}
```
We get ...
```
error: items in unadorned `extern` blocks cannot have safety qualifiers
--> test.rs:3:5
|
3 | pub safe fn bar();
| ^^^^^^^^^^^^^^^^^^
|
help: add unsafe to this `extern` block
|
1 | unsafe extern {
| ++++++
error[E0658]: `unsafe extern {}` blocks and `safe` keyword are experimental
--> test.rs:3:9
|
3 | pub safe fn bar();
| ^^^^
|
= note: see issue #123743 <https://github.com/rust-lang/rust/issues/123743> for more information
= help: add `#![feature(unsafe_extern_blocks)]` to the crate attributes to enable
error: aborting due to 2 previous errors
For more information about this error, try `rustc --explain E0658`.
```
And then making the extern block unsafe, we get ...
```
error: extern block cannot be declared unsafe
--> test.rs:1:1
|
1 | unsafe extern {
| ^^^^^^
|
= note: see issue #123743 <https://github.com/rust-lang/rust/issues/123743> for more information
= help: add `#![feature(unsafe_extern_blocks)]` to the crate attributes to enable
error: items in unadorned `extern` blocks cannot have safety qualifiers
--> test.rs:3:5
|
3 | pub safe fn bar();
| ^^^^^^^^^^^^^^^^^^
error[E0658]: `unsafe extern {}` blocks and `safe` keyword are experimental
--> test.rs:3:9
|
3 | pub safe fn bar();
| ^^^^
|
= note: see issue #123743 <https://github.com/rust-lang/rust/issues/123743> for more information
= help: add `#![feature(unsafe_extern_blocks)]` to the crate attributes to enable
error: aborting due to 3 previous errors
For more information about this error, try `rustc --explain E0658`.
```
r? ``@compiler-errors``
Update AST validation module docs
Drive-by doc update for AST validation pass:
- Syntax extensions are replaced by proc macros.
- Add rationale for why AST validation pass need to be run
post-expansion and why the pass is needed in the first place.
This was discussed during this week's [rustc-dev-guide reading club](https://rust-lang.zulipchat.com/#narrow/stream/196385-t-compiler.2Fwg-rustc-dev-guide), and the rationale was explained by cc ``````@bjorn3.``````
`StaticForeignItem` and `StaticItem` are the same
The struct `StaticItem` and `StaticForeignItem` are the same, so remove `StaticForeignItem`. Having them be separate is unique to `static` items -- unlike `ForeignItemKind::{Fn,TyAlias}`, which use the normal AST item.
r? ``@spastorino`` or ``@oli-obk``
We already do this for a number of crates, e.g. `rustc_middle`,
`rustc_span`, `rustc_metadata`, `rustc_span`, `rustc_errors`.
For the ones we don't, in many cases the attributes are a mess.
- There is no consistency about order of attribute kinds (e.g.
`allow`/`deny`/`feature`).
- Within attribute kind groups (e.g. the `feature` attributes),
sometimes the order is alphabetical, and sometimes there is no
particular order.
- Sometimes the attributes of a particular kind aren't even grouped
all together, e.g. there might be a `feature`, then an `allow`, then
another `feature`.
This commit extends the existing sorting to all compiler crates,
increasing consistency. If any new attribute line is added there is now
only one place it can go -- no need for arbitrary decisions.
Exceptions:
- `rustc_log`, `rustc_next_trait_solver` and `rustc_type_ir_macros`,
because they have no crate attributes.
- `rustc_codegen_gcc`, because it's quasi-external to rustc (e.g. it's
ignored in `rustfmt.toml`).
Rename HIR `TypeBinding` to `AssocItemConstraint` and related cleanup
Rename `hir::TypeBinding` and `ast::AssocConstraint` to `AssocItemConstraint` and update all items and locals using the old terminology.
Motivation: The terminology *type binding* is extremely outdated. "Type bindings" not only include constraints on associated *types* but also on associated *constants* (feature `associated_const_equality`) and on RPITITs of associated *functions* (feature `return_type_notation`). Hence the word *item* in the new name. Furthermore, the word *binding* commonly refers to a mapping from a binder/identifier to a "value" for some definition of "value". Its use in "type binding" made sense when equality constraints (e.g., `AssocTy = Ty`) were the only kind of associated item constraint. Nowadays however, we also have *associated type bounds* (e.g., `AssocTy: Bound`) for which the term *binding* doesn't make sense.
---
Old terminology (HIR, rustdoc):
```
`TypeBinding`: (associated) type binding
├── `Constraint`: associated type bound
└── `Equality`: (associated) equality constraint (?)
├── `Ty`: (associated) type binding
└── `Const`: associated const equality (constraint)
```
Old terminology (AST, abbrev.):
```
`AssocConstraint`
├── `Bound`
└── `Equality`
├── `Ty`
└── `Const`
```
New terminology (AST, HIR, rustdoc):
```
`AssocItemConstraint`: associated item constraint
├── `Bound`: associated type bound
└── `Equality`: associated item equality constraint OR associated item binding (for short)
├── `Ty`: associated type equality constraint OR associated type binding (for short)
└── `Const`: associated const equality constraint OR associated const binding (for short)
```
r? compiler-errors
Support C23's Variadics Without a Named Parameter
Fixes#123773
This PR removes the static check that disallowed extern functions
with ellipsis (varargs) as the only parameter since this is now
valid in C23.
This will not break any existing code as mentioned in the proposal
document: https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2975.pdf.
Also, adds a doc comment for `check_decl_cvariadic_pos()` and
fixes the name of the function (`varadic` -> `variadic`).
Translation of the lint message happens when the actual diagnostic is
created, not when the lint is buffered. Generating the message from
BuiltinLintDiag ensures that all required data to construct the message
is preserved in the LintBuffer, eventually allowing the messages to be
moved to fluent.
Remove the `msg` field from BufferedEarlyLint, it is either generated
from the data in the BuiltinLintDiag or stored inside
BuiltinLintDiag::Normal.
- Syntax extensions are replaced by proc macros.
- Add rationale for why AST validation pass need to be run
post-expansion and why the pass is needed in the first place.
This PR removes the static check that disallowed extern functions
with ellipsis (varargs) as the only parameter since this is now
valid in C23.
Also, adds a doc comment for `check_decl_cvariadic_pos()` and
fixes the name of the function (`varadic` -> `variadic`).
Improve diagnostic by suggesting to remove visibility qualifier
Resolves#123529
This PR improve diagnostic by suggesting to remove visibility qualifier.
compiler: fix few unused_peekable and needless_pass_by_ref_mut clippy lints
This fixes few instances of `unused_peekable` and `needless_pass_by_ref_mut`. While i expected to fix more warnings, `needless_pass_by_ref_mut` produced too much for one PR, so i stopped here.
Better reviewed commit by commit, as fixes splitted by chunks.
warning: this argument is a mutable reference, but not used mutably
--> compiler\rustc_session\src\config.rs:2013:16
|
2013 | early_dcx: &mut EarlyDiagCtxt,
| ^^^^^^^^^^^^^^^^^^ help: consider changing to: `&EarlyDiagCtxt`
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#needless_pass_by_ref_mut
warning: this argument is a mutable reference, but not used mutably
--> compiler\rustc_ast_passes\src\ast_validation.rs:1555:11
|
1555 | this: &mut AstValidator<'_>,
| ^^^^^^^^^^^^^^^^^^^^^ help: consider changing to: `&AstValidator<'_>`
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#needless_pass_by_ref_mut
warning: this argument is a mutable reference, but not used mutably
--> compiler\rustc_infer\src\infer\snapshot\fudge.rs:16:12
|
16 | table: &mut UnificationTable<'_, 'tcx, T>,
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider changing to: `&UnificationTable<'_, 'tcx, T>`
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#needless_pass_by_ref_mut
warning: this argument is a mutable reference, but not used mutably
--> compiler\rustc_expand\src\expand.rs:961:13
|
961 | parser: &mut Parser<'a>,
| ^^^^^^^^^^^^^^^ help: consider changing to: `&Parser<'a>`
|
= warning: changing this function will impact semver compatibility
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#needless_pass_by_ref_mut
Experimental feature postfix match
This has a basic experimental implementation for the RFC postfix match (rust-lang/rfcs#3295, #121618). [Liaison is](https://rust-lang.zulipchat.com/#narrow/stream/213817-t-lang/topic/Postfix.20Match.20Liaison/near/423301844) ```@scottmcm``` with the lang team's [experimental feature gate process](https://github.com/rust-lang/lang-team/blob/master/src/how_to/experiment.md).
This feature has had an RFC for a while, and there has been discussion on it for a while. It would probably be valuable to see it out in the field rather than continue discussing it. This feature also allows to see how popular postfix expressions like this are for the postfix macros RFC, as those will take more time to implement.
It is entirely implemented in the parser, so it should be relatively easy to remove if needed.
This PR is split in to 5 commits to ease review.
1. The implementation of the feature & gating.
2. Add a MatchKind field, fix uses, fix pretty.
3. Basic rustfmt impl, as rustfmt crashes upon seeing this syntax without a fix.
4. Add new MatchSource to HIR for Clippy & other HIR consumers
Stabilize associated type bounds (RFC 2289)
This PR stabilizes associated type bounds, which were laid out in [RFC 2289]. This gives us a shorthand to express nested type bounds that would otherwise need to be expressed with nested `impl Trait` or broken into several `where` clauses.
### What are we stabilizing?
We're stabilizing the associated item bounds syntax, which allows us to put bounds in associated type position within other bounds, i.e. `T: Trait<Assoc: Bounds...>`. See [RFC 2289] for motivation.
In all position, the associated type bound syntax expands into a set of two (or more) bounds, and never anything else (see "How does this differ[...]" section for more info).
Associated type bounds are stabilized in four positions:
* **`where` clauses (and APIT)** - This is equivalent to breaking up the bound into two (or more) `where` clauses. For example, `where T: Trait<Assoc: Bound>` is equivalent to `where T: Trait, <T as Trait>::Assoc: Bound`.
* **Supertraits** - Similar to above, `trait CopyIterator: Iterator<Item: Copy> {}`. This is almost equivalent to breaking up the bound into two (or more) `where` clauses; however, the bound on the associated item is implied whenever the trait is used. See #112573/#112629.
* **Associated type item bounds** - This allows constraining the *nested* rigid projections that are associated with a trait's associated types. e.g. `trait Trait { type Assoc: Trait2<Assoc2: Copy>; }`.
* **opaque item bounds (RPIT, TAIT)** - This allows constraining associated types that are associated with the opaque without having to *name* the opaque. For example, `impl Iterator<Item: Copy>` defines an iterator whose item is `Copy` without having to actually name that item bound.
The latter three are not expressible in surface Rust (though for associated type item bounds, this will change in #120752, which I don't believe should block this PR), so this does represent a slight expansion of what can be expressed in trait bounds.
### How does this differ from the RFC?
Compared to the RFC, the current implementation *always* desugars associated type bounds to sets of `ty::Clause`s internally. Specifically, it does *not* introduce a position-dependent desugaring as laid out in [RFC 2289], and in particular:
* It does *not* desugar to anonymous associated items in associated type item bounds.
* It does *not* desugar to nested RPITs in RPIT bounds, nor nested TAITs in TAIT bounds.
This position-dependent desugaring laid out in the RFC existed simply to side-step limitations of the trait solver, which have mostly been fixed in #120584. The desugaring laid out in the RFC also added unnecessary complication to the design of the feature, and introduces its own limitations to, for example:
* Conditionally lowering to nested `impl Trait` in certain positions such as RPIT and TAIT means that we inherit the limitations of RPIT/TAIT, namely lack of support for higher-ranked opaque inference. See this code example: https://github.com/rust-lang/rust/pull/120752#issuecomment-1979412531.
* Introducing anonymous associated types makes traits no longer object safe, since anonymous associated types are not nameable, and all associated types must be named in `dyn` types.
This last point motivates why this PR is *not* stabilizing support for associated type bounds in `dyn` types, e.g, `dyn Assoc<Item: Bound>`. Why? Because `dyn` types need to have *concrete* types for all associated items, this would necessitate a distinct lowering for associated type bounds, which seems both complicated and unnecessary compared to just requiring the user to write `impl Trait` themselves. See #120719.
### Implementation history:
Limited to the significant behavioral changes and fixes and relevant PRs, ping me if I left something out--
* #57428
* #108063
* #110512
* #112629
* #120719
* #120584Closes#52662
[RFC 2289]: https://rust-lang.github.io/rfcs/2289-associated-type-bounds.html
Includes related tests and documentation pages.
Michael Goulet: Don't issue feature error in resolver for f16/f128
unless finalize
Co-authored-by: Michael Goulet <michael@errs.io>
AST validation: Improve handling of inherent impls nested within functions and anon consts
Minimal fix for issue #121607 extracted from PR #120698 for ease of backporting and since I'd like to improve PR #120698 in such a way that it makes AST validator truly robust against such sort of regressions (AST validator is generally *beyond* footgun-y atm). The current version of PR #120698 sort of does that already but there's still room for improvement.
Fixes#89342.
Fixes [after beta-backport] #121607.
Partially addresses #119924 (#120698 aims to fully fix it).
---
### Explainer
The last commit of PR #119505 regressed issue #121607.
Previously we would reject visibilities on associated items with `visibility_not_permitted` if we were in a trait (by checking the parameter `ctxt` of `visit_assoc_item` which was 100% accurate) or if we were in a trait impl (by checking a flag called `in_trait_impl` tracked in `AstValidator` which was/is only accurate if the visitor methods correctly updated it which isn't actually the case giving rise to the old open issue #89342).
In PR #119505, I moved even more state into the `AstValidator` by generalizing the flag `in_trait_impl` to `trait_or_trait_impl` to be able to report more precise diagnostics (modeling *Trait | TraitImpl*). However since we/I didn't update `trait_or_trait_impl` in all places to reflect reality (similar to us not updating `in_trait_impl` before), this lead to https://github.com/rust-lang/rust/issues/121607#issuecomment-1963084636 getting wrongfully rejected. Since PR #119505 we reject visibilities if the “globally tracked” (wrt. to `AstValidator`) `outer_trait_or_trait_impl` is `Some`.
Crucially, when visiting an inherent impl, I never reset `outer_trait_or_trait_impl` back to `None` leading us to believe that `bar` in the stack [`trait Foo` > `fn foo` > `impl Bar` > `pub fn bar`] (from the MCVE) was an inherent associated item (we saw `trait Foo` but not `impl Bar` before it).
The old open issue #89342 is caused by the aforementioned issue of us never updating `in_trait_impl` prior to my PR #119505 / `outer_trait_or_trait` after my PR. Stack: [`impl Default for Foo` > `{` > `impl Foo` > `pub const X`] (we only saw `impl Default for Foo` but not the `impl Foo` before it).
---
This PR is only meant to be a *hot fix*. I plan on completely *rewriting* `AstValidator` from the ground up to not rely on “globally tracked” state like this or at least make it close to impossible to forget updating it when descending into nested items (etc.). Other visitors do a way better job at that (e.g. AST lowering). I actually plan on experimenting with moving more and more logic from `AstValidator` into the AST lowering pass/stage/visitor to follow the [Parse, don't validate](https://lexi-lambda.github.io/blog/2019/11/05/parse-don-t-validate/) “pattern”.
---
r? `@compiler-errors`
Stabilize the `#[diagnostic]` namespace and `#[diagnostic::on_unimplemented]` attribute
This PR stabilizes the `#[diagnostic]` attribute namespace and a minimal option of the `#[diagnostic::on_unimplemented]` attribute.
The `#[diagnostic]` attribute namespace is meant to provide a home for attributes that allow users to influence error messages emitted by the compiler. The compiler is not guaranteed to use any of this hints, however it should accept any (non-)existing attribute in this namespace and potentially emit lint-warnings for unused attributes and options. This is meant to allow discarding certain attributes/options in the future to allow fundamental changes to the compiler without the need to keep then non-meaningful options working.
The `#[diagnostic::on_unimplemented]` attribute is allowed to appear on a trait definition. This allows crate authors to hint the compiler to emit a specific error message if a certain trait is not implemented. For the `#[diagnostic::on_unimplemented]` attribute the following options are implemented:
* `message` which provides the text for the top level error message
* `label` which provides the text for the label shown inline in the broken code in the error message
* `note` which provides additional notes.
The `note` option can appear several times, which results in several note messages being emitted. If any of the other options appears several times the first occurrence of the relevant option specifies the actually used value. Any other occurrence generates an lint warning. For any other non-existing option a lint-warning is generated.
All three options accept a text as argument. This text is allowed to contain format parameters referring to generic argument or `Self` by name via the `{Self}` or `{NameOfGenericArgument}` syntax. For any non-existing argument a lint warning is generated.
This allows to have a trait definition like:
```rust
#[diagnostic::on_unimplemented(
message = "My Message for `ImportantTrait<{A}>` is not implemented for `{Self}`",
label = "My Label",
note = "Note 1",
note = "Note 2"
)]
trait ImportantTrait<A> {}
```
which then generates for the following code
```rust
fn use_my_trait(_: impl ImportantTrait<i32>) {}
fn main() {
use_my_trait(String::new());
}
```
this error message:
```
error[E0277]: My Message for `ImportantTrait<i32>` is not implemented for `String`
--> src/main.rs:14:18
|
14 | use_my_trait(String::new());
| ------------ ^^^^^^^^^^^^^ My Label
| |
| required by a bound introduced by this call
|
= help: the trait `ImportantTrait<i32>` is not implemented for `String`
= note: Note 1
= note: Note 2
```
[Playground with the unstable feature](https://play.rust-lang.org/?version=nightly&mode=debug&edition=2021&gist=05133acce8e1d163d481e97631f17536)
Fixes#111996
Rework `untranslatable_diagnostic` lint
Currently it only checks calls to functions marked with `#[rustc_lint_diagnostics]`. This PR changes it to check calls to any function with an `impl Into<{D,Subd}iagnosticMessage>` parameter. This greatly improves its coverage and doesn't rely on people remembering to add `#[rustc_lint_diagnostics]`. It also lets us add `#[rustc_lint_diagnostics]` to a number of functions that don't have an `impl Into<{D,Subd}iagnosticMessage>`, such as `Diag::span`.
r? ``@davidtwco``
Currently it only checks calls to functions marked with
`#[rustc_lint_diagnostics]`. This commit changes it to check calls to
any function with an `impl Into<{D,Subd}iagMessage>` parameter. This
greatly improves its coverage and doesn't rely on people remembering to
add `#[rustc_lint_diagnostics]`.
The commit also adds `#[allow(rustc::untranslatable_diagnostic)`]
attributes to places that need it that are caught by the improved lint.
These places that might be easy to convert to translatable diagnostics.
Finally, it also:
- Expands and corrects some comments.
- Does some minor formatting improvements.
- Adds missing `DecorateLint` cases to
`tests/ui-fulldeps/internal-lints/diagnostics.rs`.
Existing names for values of this type are `sess`, `parse_sess`,
`parse_session`, and `ps`. `sess` is particularly annoying because
that's also used for `Session` values, which are often co-located, and
it can be difficult to know which type a value named `sess` refers to.
(That annoyance is the main motivation for this change.) `psess` is nice
and short, which is good for a name used this much.
The commit also renames some `parse_sess_created` values as
`psess_created`.
This PR stabilizes the `#[diagnostic]` attribute namespace and a minimal
option of the `#[diagnostic::on_unimplemented]` attribute.
The `#[diagnostic]` attribute namespace is meant to provide a home for
attributes that allow users to influence error messages emitted by the
compiler. The compiler is not guaranteed to use any of this hints,
however it should accept any (non-)existing attribute in this namespace
and potentially emit lint-warnings for unused attributes and options.
This is meant to allow discarding certain attributes/options in the
future to allow fundamental changes to the compiler without the need to
keep then non-meaningful options working.
The `#[diagnostic::on_unimplemented]` attribute is allowed to appear
on a trait definition. This allows crate authors to hint the compiler
to emit a specific error message if a certain trait is not implemented.
For the `#[diagnostic::on_unimplemented]` attribute the following
options are implemented:
* `message` which provides the text for the top level error message
* `label` which provides the text for the label shown inline in the
broken code in the error message
* `note` which provides additional notes.
The `note` option can appear several times, which results in several
note messages being emitted. If any of the other options appears several
times the first occurrence of the relevant option specifies the actually
used value. Any other occurrence generates an lint warning. For any
other non-existing option a lint-warning is generated.
All three options accept a text as argument. This text is allowed to
contain format parameters referring to generic argument or `Self` by
name via the `{Self}` or `{NameOfGenericArgument}` syntax. For any
non-existing argument a lint warning is generated.
Tracking issue: #111996
If we abort immediately after complaining about the obsolete `impl Trait
for ..` syntax, then we avoid reaching HIR lowering. This means we can
use `TyKind::Dummy` instead of `TyKind::Err`.
Currently many diagnostic modifier methods are available on both
`Diagnostic` and `DiagnosticBuilder`. This commit removes most of them
from `Diagnostic`. To minimize the diff size, it keeps them within
`diagnostic.rs` but changes the surrounding `impl Diagnostic` block to
`impl DiagnosticBuilder`. (I intend to move things around later, to give
a more sensible code layout.)
`Diagnostic` keeps a few methods that it still needs, like `sub`,
`arg`, and `replace_args`.
The `forward!` macro, which defined two additional methods per call
(e.g. `note` and `with_note`), is replaced by the `with_fn!` macro,
which defines one additional method per call (e.g. `with_note`). It's
now also only used when necessary -- not all modifier methods currently
need a `with_*` form. (New ones can be easily added as necessary.)
All this also requires changing `trait AddToDiagnostic` so its methods
take `DiagnosticBuilder` instead of `Diagnostic`, which leads to many
mechanical changes. `SubdiagnosticMessageOp` gains a type parameter `G`.
There are three subdiagnostics -- `DelayedAtWithoutNewline`,
`DelayedAtWithNewline`, and `InvalidFlushedDelayedDiagnosticLevel` --
that are created within the diagnostics machinery and appended to
external diagnostics. These are handled at the `Diagnostic` level, which
means it's now hard to construct them via `derive(Diagnostic)`, so
instead we construct them by hand. This has no effect on what they look
like when printed.
There are lots of new `allow` markers for `untranslatable_diagnostics`
and `diagnostics_outside_of_impl`. This is because
`#[rustc_lint_diagnostics]` annotations were present on the `Diagnostic`
modifier methods, but missing from the `DiagnosticBuilder` modifier
methods. They're now present.
This makes it more like `hir::TyKind::Err`, and avoids a
`span_delayed_bug` call in `LoweringContext::lower_ty_direct`.
It also requires adding `ast::TyKind::Dummy`, now that
`ast::TyKind::Err` can't be used for that purpose in the absence of an
error emission.
There are a couple of cases that aren't as neat as I would have liked,
marked with `FIXME` comments.
Provide more suggestions on invalid equality where bounds
```
error: equality constraints are not yet supported in `where` clauses
--> $DIR/equality-bound.rs:50:9
|
LL | IntoIterator::Item = A
| ^^^^^^^^^^^^^^^^^^^^^^ not supported
|
= note: see issue #20041 <https://github.com/rust-lang/rust/issues/20041> for more information
help: if `IntoIterator::Item` is an associated type you're trying to set, use the associated type binding syntax
|
LL ~ fn from_iter<T: IntoIterator<Item = A>>(_: T) -> Self
LL ~
|
error: equality constraints are not yet supported in `where` clauses
--> $DIR/equality-bound.rs:63:9
|
LL | T::Item = A
| ^^^^^^^^^^^ not supported
|
= note: see issue #20041 <https://github.com/rust-lang/rust/issues/20041> for more information
help: if `IntoIterator::Item` is an associated type you're trying to set, use the associated type binding syntax
|
LL ~ fn from_iter<T: IntoIterator<Item = A>>(_: T) -> Self
LL ~
|
```
Fix#68982.
