Fully implement or-pattern parsing
Builds upon the initial parsing in https://github.com/rust-lang/rust/pull/61708 to fully implement or-pattern (`p | q`) parsing as specified in [the grammar section of RFC 2535](https://github.com/rust-lang/rfcs/blob/master/text/2535-or-patterns.md#grammar).
Noteworthy:
- We allow or-patterns in `[p | q, ...]`.
- We allow or-patterns in `let` statements and `for` expressions including with leading `|`.
- We improve recovery for `p || q` (+ tests for that in `multiple-pattern-typo.rs`).
- We improve recovery for `| p | q` in inner patterns (tests in `or-patterns-syntactic-fail.rs`).
- We rigorously test or-pattern parsing (in `or-patterns-syntactic-{pass,fail}.rs`).
- We harden the feature gating tests.
- We do **_not_** change `ast.rs`. That is, `ExprKind::Let.0` and `Arm.pats` still accept `Vec<P<Pat>>`.
I was starting work on that but it would be cleaner to do this in a separate PR so this one has a narrower scope.
cc @dlrobertson
cc the tracking issue https://github.com/rust-lang/rust/issues/54883.
r? @estebank
Move `Resolver` fields specific to late resolution to the new visitor.
The `current_module` field from `Resolver` is replaced with two `current_module`s in `LateResolutionVisitor` and `BuildReducedGraphVisitor`.
Outside of those visitors `current_module` is replaced by passing `parent_scope` to more functions and using the parent module from it.
Visibility resolution no longer have access to later resolution methods and has to use early resolution, so its diagnostics in case of errors regress slightly.
Suggest trait bound on type parameter when it is unconstrained
Given
```
trait Foo { fn method(&self) {} }
fn call_method<T>(x: &T) {
x.method()
}
```
suggest constraining `T` with `Foo`.
Fix#21673, fix#41030.
resolve: Improve candidate search for unresolved macro suggestions
Use same scope visiting machinery for both collecting suggestion candidates and actually resolving the names.
The PR is better read in per-commit fashion with whitespace changes ignored (the first commit in particular moves some code around).
This should be the last pre-requisite for https://github.com/rust-lang/rust/pull/62086.
r? @davidtwco
Normally `#![feature(...)]` shouldn't change behavior, but custom attributes in particular are in the process of retirement, and we should not produce a message telling to enable them.
It also helps with unifying diagnostics for unresolved macros.
When encountering code where type inference fails, add more actionable
information:
```
fn main() {
let foo = Vec::new();
}
```
```
error[E0282]: type annotations needed for `std::vec::Vec<_>`
--> $DIR/vector-no-ann.rs:2:16
|
LL | let foo = Vec::new();
| --- ^^^^^^^^ cannot infer type for `T`
| |
| consider giving `foo` the type `std::vec::Vec<_>` with the type parameter `T` specified
```
We still need to modify type printing to optionally accept a
`TypeVariableTable` in order to properly print `std::vec::Vec<T>`.
CC #25633.
This commit extends existing suggestions to prefix unused variable
bindings in match arms with an underscore so that it applies to all
patterns in a match arm.
