Make `ptr_cast_add_auto_to_object` lint into hard error
In Rust 1.81, we added a FCW lint (including linting in dependencies) against pointer casts that add an auto trait to dyn bounds. This was part of work making casts of pointers involving trait objects stricter, and was part of the work needed to restabilize trait upcasting.
We considered just making this a hard error, but opted against it at that time due to breakage found by crater. This breakage was mostly due to the `anymap` crate which has been a persistent problem for us.
It's now a year later, and the fact that this is not yet a hard error is giving us pause about stabilizing arbitrary self types and `derive(CoercePointee)`. So let's see about making a hard error of this.
r? ghost
cc ```@adetaylor``` ```@Darksonn``` ```@BoxyUwU``` ```@RalfJung``` ```@compiler-errors``` ```@oli-obk``` ```@WaffleLapkin```
Related:
- https://github.com/rust-lang/rust/pull/135881
- https://github.com/rust-lang/rust/issues/136702
- https://github.com/rust-lang/rust/pull/136776
Tracking:
- https://github.com/rust-lang/rust/issues/127323
- https://github.com/rust-lang/rust/issues/44874
- https://github.com/rust-lang/rust/issues/123430
In Rust 1.81, we added a FCW lint (including linting in dependencies)
against pointer casts that add an auto trait to dyn bounds. This was
part of work making casts of pointers involving trait objects stricter
which was needed to restabilize trait upcasting.
We considered just making this a hard error at the time, but opted
against it due to breakage found by crater. This breakage was mostly
due to the `anymap` crate which has been a persistent problem for us.
It's now a year later, and the fact that this is not yet a hard error
is giving us pause about stabilizing arbitrary self types and
`derive(CoercePointee)`. So let's now make a hard error of this.
Detect when a manual `Default` implementation isn't using the existing default field values and suggest using `..` instead:
```
error: `Default` impl doesn't use the declared default field values
--> $DIR/manual-default-impl-could-be-derived.rs:14:1
|
LL | / impl Default for A {
LL | | fn default() -> Self {
LL | | A {
LL | | y: 0,
| | - this field has a default value
... |
LL | | }
| |_^
|
= help: use the default values in the `impl` with `Struct { mandatory_field, .. }` to avoid them diverging over time
note: the lint level is defined here
--> $DIR/manual-default-impl-could-be-derived.rs:5:9
|
LL | #![deny(default_overrides_default_fields)]
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
```
`CheckAttrVisitor::check_doc_keyword` checks `#[doc(keyword = "..")]`
attributes to ensure they are on an empty module, and that the value is
a non-empty identifier.
The `rustc::existing_doc_keyword` lint checks these attributes to ensure
that the value is the name of a keyword.
It's silly to have two different checking mechanisms for these
attributes. This commit does the following.
- Changes `check_doc_keyword` to check that the value is the name of a
keyword (avoiding the need for the identifier check, which removes a
dependency on `rustc_lexer`).
- Removes the lint.
- Updates tests accordingly.
There is one hack: the `SelfTy` FIXME case used to used to be handled by
disabling the lint, but now is handled with a special case in
`is_doc_keyword`. That hack will go away if/when the FIXME is fixed.
Co-Authored-By: Guillaume Gomez <guillaume1.gomez@gmail.com>
take 2
open up coroutines
tweak the wordings
the lint works up until 2021
We were missing one case, for ADTs, which was
causing `Result` to yield incorrect results.
only include field spans with significant types
deduplicate and eliminate field spans
switch to emit spans to impl Drops
Co-authored-by: Niko Matsakis <nikomat@amazon.com>
collect drops instead of taking liveness diff
apply some suggestions and add explantory notes
small fix on the cache
let the query recurse through coroutine
new suggestion format with extracted variable name
fine-tune the drop span and messages
bugfix on runtime borrows
tweak message wording
filter out ecosystem types earlier
apply suggestions
clippy
check lint level at session level
further restrict applicability of the lint
translate bid into nop for stable mir
detect cycle in type structure
Lint against getting pointers from immediately dropped temporaries
Fixes#123613
## Changes:
1. New lint: `dangling_pointers_from_temporaries`. Is a generalization of `temporary_cstring_as_ptr` for more types and more ways to get a temporary.
2. `temporary_cstring_as_ptr` is removed and marked as renamed to `dangling_pointers_from_temporaries`.
3. `clippy::temporary_cstring_as_ptr` is marked as renamed to `dangling_pointers_from_temporaries`.
4. Fixed a false positive[^fp] for when the pointer is not actually dangling because of lifetime extension for function/method call arguments.
5. `core::cell::Cell` is now `rustc_diagnostic_item = "Cell"`
## Questions:
- [ ] Instead of manually checking for a list of known methods and diagnostic items, maybe add some sort of annotation to those methods in library and check for the presence of that annotation? https://github.com/rust-lang/rust/pull/128985#issuecomment-2318714312
## Known limitations:
### False negatives[^fn]:
See the comments in `compiler/rustc_lint/src/dangling.rs`
1. Method calls that are not checked for:
- `temporary_unsafe_cell.get()`
- `temporary_sync_unsafe_cell.get()`
2. Ways to get a temporary that are not recognized:
- `owning_temporary.field`
- `owning_temporary[index]`
3. No checks for ref-to-ptr conversions:
- `&raw [mut] temporary`
- `&temporary as *(const|mut) _`
- `ptr::from_ref(&temporary)` and friends
[^fn]: lint **should** be emitted, but **is not**
[^fp]: lint **should not** be emitted, but **is**
(Big performance change) Do not run lints that cannot emit
Before this change, adding a lint was a difficult matter because it always had some overhead involved. This was because all lints would run, no matter their default level, or if the user had `#![allow]`ed them. This PR changes that. This change would improve both the Rust lint infrastructure and Clippy, but Clippy will see the most benefit, as it has about 900 registered lints (and growing!)
So yeah, with this little patch we filter all lints pre-linting, and remove any lint that is either:
- Manually `#![allow]`ed in the whole crate,
- Allowed in the command line, or
- Not manually enabled with `#[warn]` or similar, and its default level is `Allow`
As some lints **need** to run, this PR also adds **loadbearing lints**. On a lint declaration, you can use the ``@eval_always` = true` marker to label it as loadbearing. A loadbearing lint will never be filtered (it will always run)
Fixes#106983
Before this change, adding a lint was a difficult matter
because it always had some overhead involved. This was
because all lints would run, no matter their default level,
or if the user had #![allow]ed them. This PR changes that
Make deprecated_cfg_attr_crate_type_name a hard error
Turns the forward compatibility lint added by #83744 into a hard error, so now, while the `#![crate_name]` and `#![crate_type]` attributes are still allowed in raw form, they are now forbidden to be nested inside a `#![cfg_attr()]` attribute.
The following will now be an error:
```Rust
#![cfg_attr(foo, crate_name = "foobar")]
#![cfg_attr(foo, crate_type = "bin")]
```
This code will continue working and is not deprecated:
```Rust
#![crate_name = "foobar"]
#![crate_type = "lib"]
```
The reasoning for this is explained in #83744: it allows us to not have to cfg-expand in order to determine the crate's type and name.
As of filing the PR, exactly two years have passed since #99784 has been merged, which has turned the lint's default warning level into an error, so there has been ample time to move off the now-forbidden syntax.
cc #91632 - tracking issue for the lint
const-eval interning: accept interior mutable pointers in final value
…but keep rejecting mutable references
This fixes https://github.com/rust-lang/rust/issues/121610 by no longer firing the lint when there is a pointer with interior mutability in the final value of the constant. On stable, such pointers can be created with code like:
```rust
pub enum JsValue {
Undefined,
Object(Cell<bool>),
}
impl Drop for JsValue {
fn drop(&mut self) {}
}
// This does *not* get promoted since `JsValue` has a destructor.
// However, the outer scope rule applies, still giving this 'static lifetime.
const UNDEFINED: &JsValue = &JsValue::Undefined;
```
It's not great to accept such values since people *might* think that it is legal to mutate them with unsafe code. (This is related to how "infectious" `UnsafeCell` is, which is a [wide open question](https://github.com/rust-lang/unsafe-code-guidelines/issues/236).) However, we [explicitly document](https://doc.rust-lang.org/reference/behavior-considered-undefined.html) that things created by `const` are immutable. Furthermore, we also accept the following even more questionable code without any lint today:
```rust
let x: &'static Option<Cell<i32>> = &None;
```
This is even more questionable since it does *not* involve a `const`, and yet still puts the data into immutable memory. We could view this as promotion [potentially introducing UB](https://github.com/rust-lang/unsafe-code-guidelines/issues/493). However, we've accepted this since ~forever and it's [too late to reject this now](https://github.com/rust-lang/rust/pull/122789); the pattern is just too useful.
So basically, if you think that `UnsafeCell` should be tracked fully precisely, then you should want the lint we currently emit to be removed, which this PR does. If you think `UnsafeCell` should "infect" surrounding `enum`s, the big problem is really https://github.com/rust-lang/unsafe-code-guidelines/issues/493 which does not trigger the lint -- the cases the lint triggers on are actually the "harmless" ones as there is an explicit surrounding `const` explaining why things end up being immutable.
What all this goes to show is that the hard error added in https://github.com/rust-lang/rust/pull/118324 (later turned into the future-compat lint that I am now suggesting we remove) was based on some wrong assumptions, at least insofar as it concerns shared references. Furthermore, that lint does not help at all for the most problematic case here where the potential UB is completely implicit. (In fact, the lint is actively in the way of [my preferred long-term strategy](https://github.com/rust-lang/unsafe-code-guidelines/issues/493#issuecomment-2028674105) for dealing with this UB.) So I think we should go back to square one and remove that error/lint for shared references. For mutable references, it does seem to work as intended, so we can keep it. Here it serves as a safety net in case the static checks that try to contain mutable references to the inside of a const initializer are not working as intended; I therefore made the check ICE to encourage users to tell us if that safety net is triggered.
Closes https://github.com/rust-lang/rust/issues/122153 by removing the lint.
Cc `@rust-lang/opsem` `@rust-lang/lang`
make writes_through_immutable_pointer a hard error
This turns the lint added in https://github.com/rust-lang/rust/pull/118324 into a hard error. This has been reported in cargo's future-compat reports since Rust 1.76 (released in February). Given that const_mut_refs is still unstable, it should be impossible to even hit this error on stable: we did accidentally stabilize some functions that can cause this error, but that got reverted in https://github.com/rust-lang/rust/pull/117905. Still, let's do a crater run just to be sure.
Given that this should only affect unstable code, I don't think it needs an FCP, but let's Cc ``@rust-lang/lang`` anyway -- any objection to making this unambiguous UB into a hard error during const-eval? This can be viewed as part of https://github.com/rust-lang/rust/pull/129195 which is already nominated for discussion.
Use `#[rustfmt::skip]` on some `use` groups to prevent reordering.
`use` declarations will be reformatted in #125443. Very rarely, there is a desire to force a group of `use` declarations together in a way that auto-formatting will break up. E.g. when you want a single comment to apply to a group. #126776 dealt with all of these in the codebase, ensuring that no comments intended for multiple `use` declarations would end up in the wrong place. But some people were unhappy with it.
This commit uses `#[rustfmt::skip]` to create these custom `use` groups in an idiomatic way for a few of the cases changed in #126776. This works because rustfmt treats any `use` item annotated with `#[rustfmt::skip]` as a barrier and won't reorder other `use` items around it.
r? `@cuviper`
Implement lint against ambiguous negative literals
This PR implements a lint against ambiguous negative literals with a literal and method calls right after it.
## `ambiguous_negative_literals`
(deny-by-default)
The `ambiguous_negative_literals` lint checks for cases that are confusing between a negative literal and a negation that's not part of the literal.
### Example
```rust,compile_fail
-1i32.abs(); // equals -1, while `(-1i32).abs()` equals 1
```
### Explanation
Method calls take precedence over unary precedence. Setting the precedence explicitly makes the code clearer and avoid potential bugs.
<details>
<summary>Old proposed lint</summary>
## `ambiguous_unary_precedence`
(deny-by-default)
The `ambiguous_unary_precedence` lint checks for use the negative unary operator with a literal and method calls.
### Example
```rust
-1i32.abs(); // equals -1, while `(-1i32).abs()` equals 1
```
### Explanation
Unary operations take precedence on binary operations and method calls take precedence over unary precedence. Setting the precedence explicitly makes the code clearer and avoid potential bugs.
</details>
-----
Note: This is a strip down version of https://github.com/rust-lang/rust/pull/117161, without the binary op precedence.
Fixes https://github.com/rust-lang/rust/issues/117155
`@rustbot` labels +I-lang-nominated
cc `@scottmcm`
r? compiler
