Add lint against ambiguous wide pointer comparisons
This PR is the resolution of https://github.com/rust-lang/rust/issues/106447 decided in https://github.com/rust-lang/rust/issues/117717 by T-lang.
## `ambiguous_wide_pointer_comparisons`
*warn-by-default*
The `ambiguous_wide_pointer_comparisons` lint checks comparison of `*const/*mut ?Sized` as the operands.
### Example
```rust
let ab = (A, B);
let a = &ab.0 as *const dyn T;
let b = &ab.1 as *const dyn T;
let _ = a == b;
```
### Explanation
The comparison includes metadata which may not be expected.
-------
This PR also drops `clippy::vtable_address_comparisons` which is superseded by this one.
~~One thing: is the current naming right? `invalid` seems a bit too much.~~
Fixes https://github.com/rust-lang/rust/issues/117717
This is an extension of the previous commit. It means the output of
something like this:
```
stringify!(let a: Vec<u32> = vec![];)
```
goes from this:
```
let a: Vec<u32> = vec![] ;
```
With this PR, it now produces this string:
```
let a: Vec<u32> = vec![];
```
remove redundant imports
detects redundant imports that can be eliminated.
for #117772 :
In order to facilitate review and modification, split the checking code and removing redundant imports code into two PR.
r? `@petrochenkov`
detects redundant imports that can be eliminated.
for #117772 :
In order to facilitate review and modification, split the checking code and
removing redundant imports code into two PR.
Introduce support for `async gen` blocks
I'm delighted to demonstrate that `async gen` block are not very difficult to support. They're simply coroutines that yield `Poll<Option<T>>` and return `()`.
**This PR is WIP and in draft mode for now** -- I'm mostly putting it up to show folks that it's possible. This PR needs a lang-team experiment associated with it or possible an RFC, since I don't think it falls under the jurisdiction of the `gen` RFC that was recently authored by oli (https://github.com/rust-lang/rfcs/pull/3513, https://github.com/rust-lang/rust/issues/117078).
### Technical note on the pre-generator-transform yield type:
The reason that the underlying coroutines yield `Poll<Option<T>>` and not `Poll<T>` (which would make more sense, IMO, for the pre-transformed coroutine), is because the `TransformVisitor` that is used to turn coroutines into built-in state machine functions would have to destructure and reconstruct the latter into the former, which requires at least inserting a new basic block (for a `switchInt` terminator, to match on the `Poll` discriminant).
This does mean that the desugaring (at the `rustc_ast_lowering` level) of `async gen` blocks is a bit more involved. However, since we already need to intercept both `.await` and `yield` operators, I don't consider it much of a technical burden.
r? `@ghost`
never_patterns: Parse match arms with no body
Never patterns are meant to signal unreachable cases, and thus don't take bodies:
```rust
let ptr: *const Option<!> = ...;
match *ptr {
None => { foo(); }
Some(!),
}
```
This PR makes rustc accept the above, and enforces that an arm has a body xor is a never pattern. This affects parsing of match arms even with the feature off, so this is delicate. (Plus this is my first non-trivial change to the parser).
~~The last commit is optional; it introduces a bit of churn to allow the new suggestions to be machine-applicable. There may be a better solution? I'm not sure.~~ EDIT: I removed that commit
r? `@compiler-errors`
Enforce `must_use` on associated types and RPITITs that have a must-use trait in bounds
Warn when an RPITIT or (un-normalized) associated type with a `#[must_use]` trait in its bounds is unused.
This is pending T-lang approval, since it changes the semantics of the `#[must_use]` attribute slightly, but I think it strictly catches more strange errors.
I could also limit this to just RPITITs, but that seems less useful.
Fixes#118444
Remove `#[rustc_host]`, use internal desugaring
Also removed a way for users to explicitly specify the host param since that isn't particularly useful. This should eliminate any pain with encoding attributes across crates and etc.
r? `@compiler-errors`
Add `never_patterns` feature gate
This PR adds the feature gate and most basic parsing for the experimental `never_patterns` feature. See the tracking issue (https://github.com/rust-lang/rust/issues/118155) for details on the experiment.
`@scottmcm` has agreed to be my lang-team liaison for this experiment.
Currently we always do this:
```
use rustc_fluent_macro::fluent_messages;
...
fluent_messages! { "./example.ftl" }
```
But there is no need, we can just do this everywhere:
```
rustc_fluent_macro::fluent_messages! { "./example.ftl" }
```
which is shorter.
The `fluent_messages!` macro produces uses of
`crate::{D,Subd}iagnosticMessage`, which means that every crate using
the macro must have this import:
```
use rustc_errors::{DiagnosticMessage, SubdiagnosticMessage};
```
This commit changes the macro to instead use
`rustc_errors::{D,Subd}iagnosticMessage`, which avoids the need for the
imports.
Add allow-by-default lint for unit bindings
### Example
```rust
#![warn(unit_bindings)]
macro_rules! owo {
() => {
let whats_this = ();
}
}
fn main() {
// No warning if user explicitly wrote `()` on either side.
let expr = ();
let () = expr;
let _ = ();
let _ = expr; //~ WARN binding has unit type
let pat = expr; //~ WARN binding has unit type
let _pat = expr; //~ WARN binding has unit type
// No warning for let bindings with unit type in macro expansions.
owo!();
// No warning if user explicitly annotates the unit type on the binding.
let pat: () = expr;
}
```
outputs
```
warning: binding has unit type `()`
--> $DIR/unit-bindings.rs:17:5
|
LL | let _ = expr;
| ^^^^-^^^^^^^^
| |
| this pattern is inferred to be the unit type `()`
|
note: the lint level is defined here
--> $DIR/unit-bindings.rs:3:9
|
LL | #![warn(unit_bindings)]
| ^^^^^^^^^^^^^
warning: binding has unit type `()`
--> $DIR/unit-bindings.rs:18:5
|
LL | let pat = expr;
| ^^^^---^^^^^^^^
| |
| this pattern is inferred to be the unit type `()`
warning: binding has unit type `()`
--> $DIR/unit-bindings.rs:19:5
|
LL | let _pat = expr;
| ^^^^----^^^^^^^^
| |
| this pattern is inferred to be the unit type `()`
warning: 3 warnings emitted
```
This lint is not triggered if any of the following conditions are met:
- The user explicitly annotates the binding with the `()` type.
- The binding is from a macro expansion.
- The user explicitly wrote `let () = init;`
- The user explicitly wrote `let pat = ();`. This is allowed for local lifetimes.
### Known Issue
It is known that this lint can trigger on some proc-macro generated code whose span returns false for `Span::from_expansion` because e.g. the proc-macro simply forwards user code spans, and otherwise don't have distinguishing syntax context compared to non-macro-generated code. For those kind of proc-macros, I believe the correct way to fix them is to instead emit identifers with span like `Span::mixed_site().located_at(user_span)`.
Closes#71432.
Make some `newtype_index!` derived impls opt-in instead of opt-out
Opt-in is the standard Rust way of doing things, and avoids some unnecessary dependencies on the `rustc_serialize` crate.
r? `@lcnr`
By default, `newtype_index!` types get a default `Encodable`/`Decodable`
impl. You can opt out of this with `custom_encodable`. Opting out is the
opposite to how Rust normally works with autogenerated (derived) impls.
This commit inverts the behaviour, replacing `custom_encodable` with
`encodable` which opts into the default `Encodable`/`Decodable` impl.
Only 23 of the 59 `newtype_index!` occurrences need `encodable`.
Even better, there were eight crates with a dependency on
`rustc_serialize` just from unused default `Encodable`/`Decodable`
impls. This commit removes that dependency from those eight crates.
Remove `feature` from the list of well known check-cfg name
This PR removes `feature` from the list of well known check-cfg.
This is done for multiple reasons:
- Cargo is the source of truth, rustc shouldn't have any knowledge of it
- It creates a conflict between Cargo and rustc when there are no features defined.
In this case Cargo won't pass any `--check-cfg` for `feature` since no feature will ever be passed, but rustc by having in it's list adds a implicit `cfg(feature, values(any()))` which is completely wrong. Having any cfg `feature` is unexpected not allow any `feature` value.
While doing this, I took the opportunity to specialise the diagnostic a bit for the case above.
r? `@petrochenkov`
Remove `--check-cfg` checking of command line `--cfg` args
Back in https://github.com/rust-lang/rust/pull/100574 we added to the `unexpected_cfgs` lint the checking of `--cfg` CLI arguments and emitted unexpected names and values for them.
The implementation works as expected, but it's usability in particular when using it in combination with Cargo+`RUSTFLAGS` as people who set `RUSTFLAGS=--cfg=tokio_unstable` (or whatever) have `unexpected_cfgs` warnings on all of their crates is debatable. ~~To fix this issue this PR proposes that we split the CLI argument checking into it's own separate allow-by-default lint: `unexpected_cli_cfgs`.~~
~~This has the advantage of letting people who want CLI warnings have them (although not by default anymore), while still linting on every unexpected cfg name and values in the code.~~
After some discussion with the Cargo team ([Zulip thread](https://rust-lang.zulipchat.com/#narrow/stream/246057-t-cargo/topic/check-cfg.20and.20RUSTFLAGS.20interaction)) and member of the compiler team (see below), I propose that we follow the suggestion from `@epage:` never check `--cfg` arguments, but still reserve us the possibility to do it later.
We would still lint on unexpected cfgs found in the source code no matter the `--cfg` args passed. This mean reverting https://github.com/rust-lang/rust/pull/100574 but NOT https://github.com/rust-lang/rust/pull/99519.
r? `@petrochenkov`
This lint is not triggered if any of the following conditions are met:
- The user explicitly annotates the binding with the `()` type.
- The binding is from a macro expansion.
- The user explicitly wrote `let () = init;`
- The user explicitly wrote `let pat = ();`. This is allowed for local
lifetimes.
