Constify trait aliases
Allow `const trait Foo = Bar + [const] Baz;` trait alias declarations. Their rules are the same as with super traits of const traits. So `[const] Baz` or `const Baz` is only required for `[const] Foo` or `const Foo` bounds respectively.
tracking issue rust-lang/rust#41517 (part of the general trait alias feature gate, but I can split it out into a separate const trait alias feature gate. I just assumed that const traits would stabilize before trait aliases, and we'd want to stabilize trait aliases together with const trait aliases at the same time)
r? ``@compiler-errors`` ``@fee1-dead``
Mark desugared range expression spans with DesugaringKind::RangeExpr
This is a prerequisite to removing `QPath::LangItem` (rust-lang/rust#115178) because otherwise there would be no way to detect a range expression in the HIR.
There are some non-obvious Clippy changes so a Clippy team review would be good.
unused_must_use: Don't warn on `Result<(), Uninhabited>` or `ControlFlow<Uninhabited, ()>`
This suppresses warnings on things like `Result<(), !>`, which helps simplify code using the common pattern of having an `Error` associated type: code will only have to check the error if there is a possibility of error.
This will, for instance, help with future refactorings of `write!` in the standard library.
As this is a user-visible change to lint behavior, it'll require a lang FCP.
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My proposal, here, is that we handle this simple case to make common patterns more usable. This does not rule out the possibility of adding more cases in the future, including general trait-based cases. However, I don't think we should make this common case wait on the more general cases. In particular, this solution does not close any doors on replacing this special case with a general case.
This would unblock some planned work in the standard library to make `write!` more usable for infallible cases (e.g. writing into a `Vec` or `String`).
Issue-125323: ICE non-ADT in struct pattern when long time constant evaluation is in for loop
This PR fixes#125323
## Context
According to the issue, the ICE happens since #121206.
In the PR, some error methods were reorganized. For example, has_errors() was renamed to has_errors_exclude_lint_errors(). However, some codes which used the original has_errors() were not switched to has_errors_exclude_lint_errors(). I finally found that report_error() in writeback.rs causes this ICE. Currently the method uses tainted_by_errors() to get guar (ErrorGuaranteed), but originally it used dcx().has_errors() but it wasn't changed to has_errors_exclude_lint_errors() when changes in #121206 were merged. I don't think I fully understand how an error is propagated, but I suppose that the error from long time constant evaluation is unexpectedly propagated other parts (in this ICE, for loop), then cause the non-ADT in struct pattern ICE.
## Change
- Fix report_error() in writeback.rs: use dcx().has_errors_exclude_lint_errors() instead of tainted_by_errors() to prevent error propagation from constant evaluation.
- Add test for the ICE
- Modify some tests to align the change: Due to this fix, E0282 error happens (or not happen anymore) in some tests.
## NOTE
The 4th commit aims to revert the fix in #123516 because I confirmed that the ICE solved by the PR doesn't happen if I modify report_error(). I think the root cause of that ICE is the same as #125323 . But I can discard this commit since we can fix#125323 without it.
Result/Option layout guarantee clarifications
- It seems worth spelling out that this guarantee allows particular transmutes.
- After the `Result` section was written, the `Option` section it referenced gained *more* guarantees, saying that `None` is represented as `[0u8; N]`. Those guarantees were not meant to apply to `Result`. Make the `Result` section more self-contained to make this more clear.
- "Type has no fields" is unclear since there is no general definition of what the fields of some arbitrary type are. Replace that by a more accurate description of the actual check implemented [here](e379c77586/compiler/rustc_lint/src/types.rs (L828-L838)).
r? `@traviscross`
mismatched_lifetime_syntax lint refactors and optimizations
I found several opportunities to return early so I'm hoping those will have a perf improvement. Otherwise, it's various refactors for simplicity.
error from const eval lint causes ICE at check_pat in late_lint, because the function expects the typeck result isn't tainted by error but it is.
To avoid the ICE, check_pat returns earlier if the typeck_result is tainted.
check_mod_deathness also has an issue from the same reason. visit_body for making live symbols expects the typeck result has no error.
So this commit adds a check in visit_nested_body to avoid the ICE.
However, if visit_nested_body just returns without doing anything, all codes with the error are marked as dead, because live_symbols is empty.
To avoid this side effect, visit_nested_body and other visit_* functions in MarkSymbolVistior should return appropriate error.
If a function returns ControlFlow::Break, live_symbols_and_ignore_derived_traits returns earlier with error,
then check_mod_deathness, the caller of the function returns earlier without pushing everything into dead_codes.
Restrict sysroot crate imports to those defined in this repo.
It's common to import dependencies from the sysroot via `extern crate` rather than use an explicit cargo dependency, when it's necessary to use the same dependency version as used by rustc itself. However, this is dangerous for crates.io crates, since rustc may not pull in the dependency on some targets, or may pull in multiple versions. In both cases, the `extern crate` fails to resolve.
To address this, re-export all such dependencies from the appropriate `rustc_*` crates, and use this alias from crates which would otherwise need to use `extern crate`.
See https://github.com/rust-lang/rust/pull/143492 for an example of the kind of issue that can occur.
It's common to import dependencies from the sysroot via `extern crate`
rather than use an explicit cargo dependency, when it's necessary to use
the same dependency version as used by rustc itself. However, this is
dangerous for crates.io crates, since rustc may not pull in the
dependency on some targets, or may pull in multiple versions. In both
cases, the `extern crate` fails to resolve.
To address this, re-export all such dependencies from the appropriate
`rustc_*` crates, and use this alias from crates which would otherwise
need to use `extern crate`.
This suppresses warnings on things like `Result<(), !>`, which helps
simplify code using the common pattern of having an `Error` associated
type: code will only have to check the error if there is a possibility
of error.
Prefer to use repeat_n over repeat().take()
More from https://github.com/rust-lang/rust/pull/147464, but batch processed with `ast-grep` to find and replace.
second commit add notes for library: affaf532f9
r? ``@RalfJung``
ignore power alignment rule on unions
fixes https://github.com/rust-lang/rust/issues/147348
The power alignment rule only applies to the non-first field of a struct, and so should not apply to unions at all.
The current code also does not consider enums (whose fields might be, morally, structs). Given that C does not actually have ADTs like this it's probably fine from a compatibility perspective, but I'll leave that to the powerpc folks.
cc `@daltenty` `@gilamn5tr`
r? compiler
Clean up `ty::Dynamic`
1. As a follow-up to PR rust-lang/rust#143036, remove `DynKind` entirely.
2. Inside HIR ty lowering, consolidate modules `dyn_compatibility` and `lint` into `dyn_trait`
* `dyn_compatibility` wasn't about dyn compatibility itself, it's about lowering trait object types
* `lint` contained dyn-Trait-specific diagnostics+lints only
Keep space if arg does not follow punctuation when lint unused parens
Fixesrust-lang/rust#138234
If the arg follows punctuation, still pass `left_pos` with `None` and no space will be added, else then pass `left_pos` with `Some(arg.span.lo())`, so that we can add the space as expected.
And `emit_unused_delims` can make sure no more space will be added if the expr follows space.
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Edited:
Directly use the `value_span` to check whether the expr removed parens will follow identifier or be followed by identifier.
