Require issue = "none" over issue = "0" in unstable attributes
These changes make the use of `issue = "none"` required in unstable attributes throughout the compiler.
Notes:
- #66299 is now in beta so `issue = "none"` is accepted.
- The `tidy` tool now fails on `issue = "0"`.
- Tests that used `issue = "0"` were changed to use `issue = "none"`, except for _one_ that asserts `issue = "0"` can still be used.
- The compiler still allows `issue = "0"` because some submodules require it, this could be disallowed once these are updated.
Resolves#41260
r? @varkor
Merge `TraitItem` & `ImplItem into `AssocItem`
In this PR we:
- Merge `{Trait,Impl}Item{Kind?}` into `AssocItem{Kind?}` as discussed in https://github.com/rust-lang/rust/issues/65041#issuecomment-538105286.
- This is done by using the cover grammar of both forms.
- In particular, it requires that we syntactically allow (under `#[cfg(FALSE)]`):
- `default`ness on `trait` items,
- `impl` items without a body / definition (`const`, `type`, and `fn`),
- and associated `type`s in `impl`s with bounds, e.g., `type Foo: Ord;`.
- The syntactic restrictions are replaced by semantic ones in `ast_validation`.
- Move syntactic restrictions around C-variadic parameters from the parser into `ast_validation`:
- `fn`s in all contexts now syntactically allow `...`,
- `...` can occur anywhere in the list syntactically (`fn foo(..., x: usize) {}`),
- and `...` can be the sole parameter (`fn foo(...) {}`.
r? @petrochenkov
Enable `loop` and `while` in constants behind a feature flag
This PR is an initial implementation of #52000. It adds a `const_loop` feature gate, which allows `while` and `loop` expressions through both HIR and MIR const-checkers if enabled. `for` expressions remain forbidden by the HIR const-checker, since they desugar to a call to `IntoIterator::into_iter`, which will be rejected anyways.
`while` loops also require [`#![feature(const_if_match)]`](https://github.com/rust-lang/rust/pull/66507), since they have a conditional built into them. The diagnostics from the HIR const checker will suggest this to the user.
r? @oli-obk
cc @rust-lang/wg-const-eval
Conditionals and loops now have unstable features, and `feature_err` has
its own error code. I think that `feature_err` should take an error code
as a parameter, but don't have the energy to make this change throughout
the codebase. Also, the error code system may be torn out entirely.
Add long error for E0631 and update ui tests.
This PR adds a long error for `E0631`, which covers errors where closure argument types are mismatched. It also updates UI tests where this error is applicable.
Part of #61137
Put back tidy check on error codes
I just realized that the tidy checks were not run anymore on the error code long explanations. This add it back.
cc @Dylan-DPC
r? @Mark-Simulacrum
