Stabilize #[diagnostic::do_not_recommend]
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lqd
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Oct 23, 2024
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what's the process for stabilizing a diagnostic attr again? i think there was one |
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There is no process yet; iirc, T-lang has expressed that they'd like to get involved in the stabilization of the first few of these attributes just to see how it goes. Ideally, after this stabilization, we should work towards establishing a better policy for this, though. @rustbot label: I-lang-nominated |
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☔ The latest upstream changes (presumably #132027) made this pull request unmergeable. Please resolve the merge conflicts. |
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Can you please post a documentation PR before stabilizing? |
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@ehuss I've opened rust-lang/reference#1663 for that |
ehuss
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Oct 24, 2024
| hir_id: HirId, | ||
| target: Target, | ||
| attr: &Attribute, | ||
| ) { | ||
| if !matches!(target, Target::Impl) { |
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Should this also be checking that the target is a trait impl and not inherent?
Otherwise it seems to accept #[diagnostic::do_not_recommend] on impl T {}
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Good catch. I've pushed 3d814b3 to fix this.
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☔ The latest upstream changes (presumably #131349) made this pull request unmergeable. Please resolve the merge conflicts. |
This PR aims to improve the testing coverage for `#[diagnostic::do_not_recommend]`. It ensures that all tests are run for the old and new solver to verify that the behaviour is the same for both variants. It also adds two new tests: * A test with 4 traits having wild card impl for each other, with alternating `#[diagnostic::do_not_recommend]` attributse * A test with a lifetime dependend wild card impl, which is something that's not supported yet
This commit adds a check that verifies that no arguments are passed to `#[diagnostic::do_not_recommend]`. If we detect arguments we emit a warning.
This commit seeks to stabilize the `#[diagnostic::do_not_recommend]` attribute. This attribute was first proposed as `#[do_not_recommend`] attribute in RFC 2397 (rust-lang/rfcs#2397). It gives the crate authors the ability to not suggest to the compiler to not show certain traits in it's error messages. With the presence of the `#[diagnostic]` tool attribute namespace it was decided to move the attribute there, as that lowers the amount of guarantees the compiler needs to give about the exact way this influences error messages. It turns the attribute into a hint which can be ignored. In addition to the original proposed functionality this attribute now also hides the marked trait in help messages ("This trait is implemented by: "). The attribute does not accept any argument and can only be placed on trait implementations. If it is placed somewhere else a lint warning is emitted and the attribute is otherwise ignored. If an argument is detected a lint warning is emitted and the argument is ignored. This follows the rules outlined by the diagnostic namespace. This attribute allows crates like diesel to improve their error messages drastically. The most common example here is the following error message: ``` error[E0277]: the trait bound `&str: Expression` is not satisfied --> /home/weiznich/Documents/rust/rust/tests/ui/diagnostic_namespace/do_not_recommend.rs:53:15 | LL | SelectInt.check("bar"); | ^^^^^ the trait `Expression` is not implemented for `&str`, which is required by `&str: AsExpression<Integer>` | = help: the following other types implement trait `Expression`: Bound<T> SelectInt note: required for `&str` to implement `AsExpression<Integer>` --> /home/weiznich/Documents/rust/rust/tests/ui/diagnostic_namespace/do_not_recommend.rs:26:13 | LL | impl<T, ST> AsExpression<ST> for T | ^^^^^^^^^^^^^^^^ ^ LL | where LL | T: Expression<SqlType = ST>, | ------------------------ unsatisfied trait bound introduced here ``` By applying the new attribute to the wild card trait implementation of `AsExpression` for `T: Expression` the error message becomes: ``` error[E0277]: the trait bound `&str: AsExpression<Integer>` is not satisfied --> $DIR/as_expression.rs:55:15 | LL | SelectInt.check("bar"); | ^^^^^ the trait `AsExpression<Integer>` is not implemented for `&str` | = help: the trait `AsExpression<Text>` is implemented for `&str` = help: for that trait implementation, expected `Text`, found `Integer` ``` which makes it much easier for users to understand that they are facing a type mismatch. Other explored example usages included * This standard library error message: rust-lang#128008 * That bevy derived example: https://github.com/rust-lang/rust/blob/e1f306899514ea80abc1d1c9f6a57762afb304a3/tests/ui/diagnostic_namespace/do_not_recommend/supress_suggestions_in_help.rs (No more tuple pyramids) Fixes rust-lang#51992
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This PR seeks to stabilize the
#[diagnostic::do_not_recommend]attribute.This attribute was first proposed as
#[do_not_recommend] attribute in RFC 2397 (rust-lang/rfcs#2397). It gives the crate authors the ability to not suggest to the compiler to not show certain traits in its error messages.With the presence of the
#[diagnostic]tool attribute namespace it was decided to move the attribute there, as that lowers the amount of guarantees the compiler needs to give about the exact way this influences error messages. It turns the attribute into a hint which can be ignored. In addition to the original proposed functionality this attribute now also hides the marked trait in help messages ("This trait is implemented by: ").The attribute does not accept any argument and can only be placed on trait implementations. If it is placed somewhere else a lint warning is emitted and the attribute is otherwise ignored. If an argument is detected a lint warning is emitted and the argument is ignored. This follows the rules outlined by the diagnostic namespace.
This attribute allows crates like diesel to improve their error messages drastically. The most common example here is the following error message:
By applying the new attribute to the wild card trait implementation of
AsExpressionforT: Expressionthe error message becomes:which makes it much easier for users to understand that they are facing a type mismatch.
Other explored example usages include:
#[diagnostic::do_not_recommend]in the standard library #128008https://github.com/rust-lang/rust/blob/e1f306899514ea80abc1d1c9f6a57762afb304a3/tests/ui/diagnostic_namespace/do_not_recommend/supress_suggestions_in_help.rs (No
more tuple pyramids)
Fixes #51992
r? @compiler-errors
This PR also adds a few more tests, makes sure that all the tests are run for the old and new trait solver and adds a check that the attribute does not contain arguments.