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8c04999226
When we encounter a `dyn Trait` that isn't object safe, look for its
implementors. If there's one, mention using it directly If there are
less than 9, mention the possibility of creating a new enum and using
that instead.
Account for object unsafe `impl Trait on dyn Trait {}`. Make a
distinction between public and sealed traits.
Fix #80194.
63 lines
2.6 KiB
Plaintext
63 lines
2.6 KiB
Plaintext
error[E0308]: `match` arms have incompatible types
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--> $DIR/wf-unsafe-trait-obj-match.rs:23:17
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LL | / match opt() {
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LL | | Some(()) => &S,
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| | -- this is found to be of type `&S`
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LL | | None => &R,
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| | ^^ expected `&S`, found `&R`
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LL | | }
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| |_____- `match` arms have incompatible types
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= note: expected reference `&S`
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found reference `&R`
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help: consider using a semicolon here, but this will discard any values in the match arms
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LL | };
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| +
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error[E0038]: the trait `Trait` cannot be made into an object
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--> $DIR/wf-unsafe-trait-obj-match.rs:26:21
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LL | Some(()) => &S,
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| ^^ `Trait` cannot be made into an object
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note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
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--> $DIR/wf-unsafe-trait-obj-match.rs:6:14
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LL | trait Trait: Sized {}
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| ----- ^^^^^ ...because it requires `Self: Sized`
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| |
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| this trait cannot be made into an object...
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= help: the following types implement the trait, consider defining an enum where each variant holds one of these types, implementing `Trait` for this new enum and using it instead:
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S
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R
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= note: required for the cast from `&S` to `&dyn Trait`
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error[E0038]: the trait `Trait` cannot be made into an object
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--> $DIR/wf-unsafe-trait-obj-match.rs:25:25
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LL | let t: &dyn Trait = match opt() {
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| _________________________^
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LL | | Some(()) => &S,
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LL | | None => &R,
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LL | | };
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| |_____^ `Trait` cannot be made into an object
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note: for a trait to be "object safe" it needs to allow building a vtable to allow the call to be resolvable dynamically; for more information visit <https://doc.rust-lang.org/reference/items/traits.html#object-safety>
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--> $DIR/wf-unsafe-trait-obj-match.rs:6:14
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LL | trait Trait: Sized {}
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| ----- ^^^^^ ...because it requires `Self: Sized`
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| |
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| this trait cannot be made into an object...
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= help: the following types implement the trait, consider defining an enum where each variant holds one of these types, implementing `Trait` for this new enum and using it instead:
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S
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R
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= note: required for the cast from `&R` to `&dyn Trait`
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error: aborting due to 3 previous errors
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Some errors have detailed explanations: E0038, E0308.
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For more information about an error, try `rustc --explain E0038`.
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