diff options
Diffstat (limited to 'library/core/src/ops/try_trait.rs')
-rw-r--r-- | library/core/src/ops/try_trait.rs | 84 |
1 files changed, 82 insertions, 2 deletions
diff --git a/library/core/src/ops/try_trait.rs b/library/core/src/ops/try_trait.rs index 02f7f62bf..10f041344 100644 --- a/library/core/src/ops/try_trait.rs +++ b/library/core/src/ops/try_trait.rs @@ -222,7 +222,87 @@ 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( +#[cfg_attr(not(bootstrap), rustc_on_unimplemented( + on( + all( + 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}`", + parent_label = "this function returns a `Result`" + ), + on( + all( + 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}`", + parent_label = "this function returns a `Result`" + ), + on( + all( + from_desugaring = "QuestionMark", + _Self = "std::option::Option<T>", + R = "std::result::Result<T, E>", + ), + message = "the `?` operator can only be used on `Option`s, not `Result`s, \ + in {ItemContext} that returns `Option`", + label = "use `.ok()?` if you want to discard the `{R}` error information", + parent_label = "this function returns an `Option`" + ), + on( + all( + 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}`", + parent_label = "this function returns an `Option`" + ), + on( + all( + from_desugaring = "QuestionMark", + _Self = "std::ops::ControlFlow<B, C>", + R = "std::ops::ControlFlow<B, C>", + ), + message = "the `?` operator in {ItemContext} that returns `ControlFlow<B, _>` \ + can only be used on other `ControlFlow<B, _>`s (with the same Break type)", + label = "this `?` produces `{R}`, which is incompatible with `{Self}`", + parent_label = "this function returns a `ControlFlow`", + note = "unlike `Result`, there's no `From`-conversion performed for `ControlFlow`" + ), + on( + all( + from_desugaring = "QuestionMark", + _Self = "std::ops::ControlFlow<B, C>", + // `R` is not a `ControlFlow`, as that case was matched previously + ), + message = "the `?` operator can only be used on `ControlFlow`s \ + in {ItemContext} that returns `ControlFlow`", + label = "this `?` produces `{R}`, which is incompatible with `{Self}`", + parent_label = "this function returns a `ControlFlow`", + ), + on( + all(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}`", + parent_label = "this function should return `Result` or `Option` to accept `?`" + ), +))] +#[cfg_attr(bootstrap, rustc_on_unimplemented( on( all( from_desugaring = "QuestionMark", @@ -301,7 +381,7 @@ pub trait Try: FromResidual { label = "cannot use the `?` operator in {ItemContext} that returns `{Self}`", enclosing_scope = "this function should return `Result` or `Option` to accept `?`" ), -)] +))] #[rustc_diagnostic_item = "FromResidual"] #[unstable(feature = "try_trait_v2", issue = "84277")] pub trait FromResidual<R = <Self as Try>::Residual> { |