diff options
Diffstat (limited to 'library/core')
| -rw-r--r-- | library/core/src/ops/mod.rs | 4 | ||||
| -rw-r--r-- | library/core/src/ops/try_trait.rs | 79 |
2 files changed, 81 insertions, 2 deletions
diff --git a/library/core/src/ops/mod.rs b/library/core/src/ops/mod.rs index 426b45a925e..4fca2898b56 100644 --- a/library/core/src/ops/mod.rs +++ b/library/core/src/ops/mod.rs @@ -187,7 +187,7 @@ pub use self::range::{Bound, RangeBounds, RangeInclusive, RangeToInclusive}; pub use self::r#try::Try; #[unstable(feature = "try_trait_transition", reason = "for bootstrap", issue = "none")] -pub use self::r#try::Try as TryV1; +pub(crate) use self::r#try::Try as TryV1; #[unstable(feature = "try_trait_v2", issue = "84277")] pub use self::try_trait::FromResidual; @@ -197,7 +197,7 @@ pub use self::try_trait::FromResidual; pub use self::try_trait::Try; #[unstable(feature = "try_trait_transition", reason = "for bootstrap", issue = "none")] -pub use self::try_trait::Try as TryV2; +pub(crate) use self::try_trait::Try as TryV2; #[unstable(feature = "generator_trait", issue = "43122")] pub use self::generator::{Generator, GeneratorState}; diff --git a/library/core/src/ops/try_trait.rs b/library/core/src/ops/try_trait.rs index 80a5800bcbb..35989d2bc05 100644 --- a/library/core/src/ops/try_trait.rs +++ b/library/core/src/ops/try_trait.rs @@ -115,6 +115,21 @@ use crate::ops::ControlFlow; /// } /// ``` #[unstable(feature = "try_trait_v2", issue = "84277")] +#[rustc_on_unimplemented( + on( + all(from_method = "from_output", from_desugaring = "TryBlock"), + message = "a `try` block must return `Result` or `Option` \ + (or another type that implements `{Try}`)", + label = "could not wrap the final value of the block as `{Self}` doesn't implement `Try`", + ), + on( + all(from_method = "branch", from_desugaring = "QuestionMark"), + message = "the `?` operator can only be applied to values \ + that implement `{Try}`", + label = "the `?` operator cannot be applied to type `{Self}`" + ) +)] +#[doc(alias = "?")] #[cfg_attr(not(bootstrap), lang = "Try")] pub trait Try: FromResidual { /// The type of the value produced by `?` when *not* short-circuiting. @@ -212,6 +227,70 @@ pub trait Try: FromResidual { /// Every `Try` type needs to be recreatable from its own associated /// `Residual` type, but can also have additional `FromResidual` implementations /// to support interconversion with other `Try` types. +#[rustc_on_unimplemented( + on( + all( + from_method = "from_residual", + from_desugaring = "QuestionMark", + _Self = "std::result::Result<T, E>", + R = "std::option::Option<std::convert::Infallible>" + ), + message = "the `?` operator can only be used on `Result`s, not `Option`s, \ + in {ItemContext} that returns `Result`", + label = "use `.ok_or(...)?` to provide an error compatible with `{Self}`", + enclosing_scope = "this function returns a `Result`" + ), + on( + all( + from_method = "from_residual", + from_desugaring = "QuestionMark", + _Self = "std::result::Result<T, E>", + ), + // There's a special error message in the trait selection code for + // `From` in `?`, so this is not shown for result-in-result errors, + // and thus it can be phrased more strongly than `ControlFlow`'s. + message = "the `?` operator can only be used on `Result`s \ + in {ItemContext} that returns `Result`", + label = "this `?` produces `{R}`, which is incompatible with `{Self}`", + enclosing_scope = "this function returns a `Result`" + ), + on( + all( + from_method = "from_residual", + from_desugaring = "QuestionMark", + _Self = "std::option::Option<T>", + ), + // `Option`-in-`Option` always works, as there's only one possible + // residual, so this can also be phrased strongly. + message = "the `?` operator can only be used on `Option`s \ + in {ItemContext} that returns `Option`", + label = "this `?` produces `{R}`, which is incompatible with `{Self}`", + enclosing_scope = "this function returns an `Option`" + ), + on( + all( + from_method = "from_residual", + from_desugaring = "QuestionMark", + _Self = "std::ops::ControlFlow<B, C>", + ), + message = "the `?` operator can only be used on `ControlFlow<B, _>`s \ + in {ItemContext} that returns `ControlFlow<B, _>`", + label = "this `?` produces `{R}`, which is incompatible with `{Self}`", + enclosing_scope = "this function returns a `ControlFlow`", + note = "unlike `Result`, there's no `From`-conversion performed for `ControlFlow`" + ), + on( + all( + from_method = "from_residual", + from_desugaring = "QuestionMark" + ), + message = "the `?` operator can only be used in {ItemContext} \ + that returns `Result` or `Option` \ + (or another type that implements `{FromResidual}`)", + label = "cannot use the `?` operator in {ItemContext} that returns `{Self}`", + enclosing_scope = "this function should return `Result` or `Option` to accept `?`" + ), +)] #[unstable(feature = "try_trait_v2", issue = "84277")] pub trait FromResidual<R = <Self as Try>::Residual> { /// Constructs the type from a compatible `Residual` type. |