d3c96f03b5
During development, a function could have a return type set that is a bare trait object by accident. We already suggest using either a boxed trait object or `impl Trait` if the return paths will allow it. We now do so too when there are *no* return paths or they all resolve to `!`. We still don't handle cases where the trait object is *not* the entirety of the return type gracefully.
27 lines
1.1 KiB
Text
27 lines
1.1 KiB
Text
error[E0746]: return type cannot have an unboxed trait object
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--> $DIR/E0746.rs:8:13
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LL | fn foo() -> dyn Trait { Struct }
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| ^^^^^^^^^ doesn't have a size known at compile-time
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= note: for information on `impl Trait`, see <https://doc.rust-lang.org/book/ch10-02-traits.html#returning-types-that-implement-traits>
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help: use `impl Trait` as the return type, as all return paths are of type `Struct`, which implements `Trait`
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LL | fn foo() -> impl Trait { Struct }
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| ^^^^^^^^^^
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error[E0746]: return type cannot have an unboxed trait object
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--> $DIR/E0746.rs:11:13
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LL | fn bar() -> dyn Trait {
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| ^^^^^^^^^ doesn't have a size known at compile-time
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= note: for information on `impl Trait`, see <https://doc.rust-lang.org/book/ch10-02-traits.html#returning-types-that-implement-traits>
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help: use `impl Trait` as the return type, as all return paths are of type `{integer}`, which implements `Trait`
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LL | fn bar() -> impl Trait {
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| ^^^^^^^^^^
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error: aborting due to 2 previous errors
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For more information about this error, try `rustc --explain E0746`.
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