This updates the standard library's documentation to use the new syntax. The
documentation is worthwhile to update as it should be more idiomatic
(particularly for features like this, which are nice for users to get acquainted
with). The general codebase is likely more hassle than benefit to update: it'll
hurt git blame, and generally updates can be done by folks updating the code if
(and when) that makes things more readable with the new format.
A few places in the compiler and library code are updated (mostly just due to
already having been done when this commit was first authored).
diagnostics: use rustc_on_unimplemented to recommend `[].iter()`
To make this work, the `#[rustc_on_unimplemented]` data needs to be used to
report method resolution errors, which is most of what this commit does.
Fixes#94581
This change is somewhat extensive, since it affects MIR -- since this is called to determine Copy vs Move -- so any test that's `no_core` needs to actually have the normal `impl`s it uses.
Treat constant values as mir::ConstantKind::Val
Another step that is necessary for the introduction of Valtrees: we don't want to treat `ty::Const` instances of kind `ty::ConstKind::Value` as `mir::ConstantKind::Ty` anymore.
r? `@oli-obk`
add `#[rustc_pass_by_value]` to more types
the only interesting changes here should be to `TransitiveRelation`, but I believe to be highly unlikely that we will ever use a non `Copy` type with this type.
To make this work, the `#[rustc_on_unimplemented]` data needs to be used to
report method resolution errors, which is most of what this commit does.
Fixes#94581
Use impl substs in `#[rustc_on_unimplemented]`
We were using the trait-ref substs instead of impl substs in `rustc_on_unimplemented`, even when computing the `rustc_on_unimplemented` attached to an impl block. Let's not do that.
This PR also untangles impl and trait def-ids in the logic in `on_unimplemented` a bit.
Fixes#94675
Clarify `Layout` interning.
`Layout` is another type that is sometimes interned, sometimes not, and
we always use references to refer to it so we can't take any advantage
of the uniqueness properties for hashing or equality checks.
This commit renames `Layout` as `LayoutS`, and then introduces a new
`Layout` that is a newtype around an `Interned<LayoutS>`. It also
interns more layouts than before. Previously layouts within layouts
(via the `variants` field) were never interned, but now they are. Hence
the lifetime on the new `Layout` type.
Unlike other interned types, these ones are in `rustc_target` instead of
`rustc_middle`. This reflects the existing structure of the code, which
does layout-specific stuff in `rustc_target` while `TyAndLayout` is
generic over the `Ty`, allowing the type-specific stuff to occur in
`rustc_middle`.
The commit also adds a `HashStable` impl for `Interned`, which was
needed. It hashes the contents, unlike the `Hash` impl which hashes the
pointer.
r? `@fee1-dead`
`Layout` is another type that is sometimes interned, sometimes not, and
we always use references to refer to it so we can't take any advantage
of the uniqueness properties for hashing or equality checks.
This commit renames `Layout` as `LayoutS`, and then introduces a new
`Layout` that is a newtype around an `Interned<LayoutS>`. It also
interns more layouts than before. Previously layouts within layouts
(via the `variants` field) were never interned, but now they are. Hence
the lifetime on the new `Layout` type.
Unlike other interned types, these ones are in `rustc_target` instead of
`rustc_middle`. This reflects the existing structure of the code, which
does layout-specific stuff in `rustc_target` while `TyAndLayout` is
generic over the `Ty`, allowing the type-specific stuff to occur in
`rustc_middle`.
The commit also adds a `HashStable` impl for `Interned`, which was
needed. It hashes the contents, unlike the `Hash` impl which hashes the
pointer.
Currently some `Allocation`s are interned, some are not, and it's very
hard to tell at a use point which is which.
This commit introduces `ConstAllocation` for the known-interned ones,
which makes the division much clearer. `ConstAllocation::inner()` is
used to get the underlying `Allocation`.
In some places it's natural to use an `Allocation`, in some it's natural
to use a `ConstAllocation`, and in some places there's no clear choice.
I've tried to make things look as nice as possible, while generally
favouring `ConstAllocation`, which is the type that embodies more
information. This does require quite a few calls to `inner()`.
The commit also tweaks how `PartialOrd` works for `Interned`. The
previous code was too clever by half, building on `T: Ord` to make the
code shorter. That caused problems with deriving `PartialOrd` and `Ord`
for `ConstAllocation`, so I changed it to build on `T: PartialOrd`,
which is slightly more verbose but much more standard and avoided the
problems.
Ensure stability directives are checked in all cases
Split off #93017
Stability and deprecation were not checked in all cases, for instance if a type error happened.
This PR moves the check earlier in the pipeline to ensure the errors are emitted in all cases.
r? `@lcnr`
improve comments for `simplify_type`
Should now correctly describe what's going on. Experimented with checking the invariant for projections
but that ended up requiring fairly involved changes. I assume that it is not possible to get unsoundness here,
at least for now and I can pretty much guarantee that it's impossible to trigger it by accident.
r? `````@nikomatsakis````` cc #92721
Implementation of the `expect` attribute (RFC 2383)
This is an implementation of the `expect` attribute as described in [RFC-2383](https://rust-lang.github.io/rfcs/2383-lint-reasons.html). The attribute allows the suppression of lint message by expecting them. Unfulfilled lint expectations (meaning no expected lint was caught) will emit the `unfulfilled_lint_expectations` lint at the `expect` attribute.
### Example
#### input
```rs
// required feature flag
#![feature(lint_reasons)]
#[expect(unused_mut)] // Will warn about an unfulfilled expectation
#[expect(unused_variables)] // Will be fulfilled by x
fn main() {
let x = 0;
}
```
#### output
```txt
warning: this lint expectation is unfulfilled
--> $DIR/trigger_lint.rs:3:1
|
LL | #[expect(unused_mut)] // Will warn about an unfulfilled expectation
| ^^^^^^^^^^
|
= note: `#[warn(unfulfilled_lint_expectations)]` on by default
```
### Implementation
This implementation introduces `Expect` as a new lint level for diagnostics, which have been expected. All lint expectations marked via the `expect` attribute are collected in the [`LintLevelsBuilder`] and assigned an ID that is stored in the new lint level. The `LintLevelsBuilder` stores all found expectations and the data needed to emit the `unfulfilled_lint_expectations` in the [`LintLevelsMap`] which is the result of the [`lint_levels()`] query.
The [`rustc_errors::HandlerInner`] is the central error handler in rustc and handles the emission of all diagnostics. Lint message with the level `Expect` are suppressed during this emission, while the expectation ID is stored in a set which marks them as fulfilled. The last step is then so simply check if all expectations collected by the [`LintLevelsBuilder`] in the [`LintLevelsMap`] have been marked as fulfilled in the [`rustc_errors::HandlerInner`]. Otherwise, a new lint message will be emitted.
The implementation of the `LintExpectationId` required some special handling to make it stable between sessions. Lints can be emitted during [`EarlyLintPass`]es. At this stage, it's not possible to create a stable identifier. The level instead stores an unstable identifier, which is later converted to a stable `LintExpectationId`.
### Followup TO-DOs
All open TO-DOs have been marked with `FIXME` comments in the code. This is the combined list of them:
* [ ] The current implementation doesn't cover cases where the `unfulfilled_lint_expectations` lint is actually expected by another `expect` attribute.
* This should be easily possible, but I wanted to get some feedback before putting more work into this.
* This could also be done in a new PR to not add to much more code to this one
* [ ] Update unstable documentation to reflect this change.
* [ ] Update unstable expectation ids in [`HandlerInner::stashed_diagnostics`](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_errors/struct.HandlerInner.html#structfield.stashed_diagnostics)
### Open questions
I also have a few open questions where I would like to get feedback on:
1. The RFC discussion included a suggestion to change the `expect` attribute to something else. (Initiated by `@Ixrec` [here](https://github.com/rust-lang/rfcs/pull/2383#issuecomment-378424091), suggestion from `@scottmcm` to use `#[should_lint(...)]` [here](https://github.com/rust-lang/rfcs/pull/2383#issuecomment-378648877)). No real conclusion was drawn on that point from my understanding. Is this still open for discussion, or was this discarded with the merge of the RFC?
2. How should the expect attribute deal with the new `force-warn` lint level?
---
This approach was inspired by a discussion with `@LeSeulArtichaut.`
RFC tracking issue: #54503
Mentoring/Implementation issue: #85549
[`LintLevelsBuilder`]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_lint/levels/struct.LintLevelsBuilder.html
[`LintLevelsMap`]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_middle/lint/struct.LintLevelMap.html
[`lint_levels()`]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_middle/ty/context/struct.TyCtxt.html#method.lint_levels
[`rustc_errors::HandlerInner`]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_errors/struct.HandlerInner.html
[`EarlyLintPass`]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_lint/trait.EarlyLintPass.html
Miri/CTFE: properly treat overflow in (signed) division/rem as UB
To my surprise, it looks like LLVM treats overflow of signed div/rem as UB. From what I can tell, MIR `Div`/`Rem` directly lowers to the corresponding LLVM operation, so to make that correct we also have to consider these overflows UB in the CTFE/Miri interpreter engine.
r? `@oli-obk`
Restore the local filter on mono item sorting
In `CodegenUnit::items_in_deterministic_order`, there's a comment that
only local HirIds should be taken into account, but #90408 removed the
`as_local` call that sets others to None. Restoring that check fixes the
s390x hangs seen in [RHBZ 2058803].
[RHBZ 2058803]: https://bugzilla.redhat.com/show_bug.cgi?id=2058803
Adt copy suggestions
Previously we've only suggested adding `Copy` bounds when the type being moved/copied is a type parameter (generic). With this PR we also suggest adding bounds when a type
- Can be copy
- All predicates that need to be satisfied for that are based on type params
i.e. we will suggest `T: Copy` for `Option<T>`, but won't suggest anything for `Option<String>`.
An example:
```rust
fn duplicate<T>(t: Option<T>) -> (Option<T>, Option<T>) {
(t, t)
}
```
New error (current compiler doesn't provide `help`:):
```text
error[E0382]: use of moved value: `t`
--> t.rs:2:9
|
1 | fn duplicate<T>(t: Option<T>) -> (Option<T>, Option<T>) {
| - move occurs because `t` has type `Option<T>`, which does not implement the `Copy` trait
2 | (t, t)
| - ^ value used here after move
| |
| value moved here
|
help: consider restricting type parameter `T`
|
1 | fn duplicate<T: Copy>(t: Option<T>) -> (Option<T>, Option<T>) {
| ++++++
```
Fixes#93623
r? ``````````@estebank``````````
``````````@rustbot`````````` label +A-diagnostics +A-suggestion-diagnostics +C-enhancement
----
I'm not at all sure if this is the right implementation for this kind of suggestion, but it seems to work :')
Direct users towards using Rust target feature names in CLI
This PR consists of a couple of changes on how we handle target features.
In particular there is a bug-fix wherein we avoid passing through features that aren't prefixed by `+` or `-` to LLVM. These appear to be causing LLVM to assert, which is pretty poor a behaviour (and also makes it pretty clear we expect feature names to be prefixed).
The other commit, I anticipate to be somewhat more controversial is outputting a warning when users specify a LLVM-specific, or otherwise unknown, feature name on the CLI. In those situations we request users to either replace it with a known Rust feature name (e.g. `bmi` -> `bmi1`) or file a feature request. I've a couple motivations for this: first of all, if users are specifying these features on the command line, I'm pretty confident there is also a need for these features to be usable via `#[cfg(target_feature)]` machinery. And second, we're growing a fair number of backends recently and having ability to provide some sort of unified-ish interface in this place seems pretty useful to me.
Sponsored by: standard.ai
In `CodegenUnit::items_in_deterministic_order`, there's a comment that
only local HirIds should be taken into account, but #90408 removed the
`as_local` call that sets others to None. Restoring that check fixes the
s390x hangs seen in [RHBZ 2058803].
[RHBZ 2058803]: https://bugzilla.redhat.com/show_bug.cgi?id=2058803
