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I encountered an instance where an `FnPtr` implemented a trait, but I was passing an `FnDef`. To the end user, there is really no way to differentiate each of them, but it is necessary to cast to the generic function in order to compile. It is thus useful to suggest `as` in the help note, (even if the Fn output implements the trait).
37 lines
1.4 KiB
Plaintext
37 lines
1.4 KiB
Plaintext
error[E0277]: the trait bound `fn(Argument) -> Return {function}: Trait` is not satisfied
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--> $DIR/issue-99875.rs:12:11
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LL | takes(function);
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| ----- ^^^^^^^^ the trait `Trait` is not implemented for fn item `fn(Argument) -> Return {function}`
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| |
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| required by a bound introduced by this call
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note: required by a bound in `takes`
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--> $DIR/issue-99875.rs:9:18
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LL | fn takes(_: impl Trait) {}
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| ^^^^^ required by this bound in `takes`
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help: the trait `Trait` is implemented for fn pointer `fn(Argument) -> Return`, try casting using `as`
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LL | takes(function as fn(Argument) -> Return);
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| +++++++++++++++++++++++++
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error[E0277]: the trait bound `[closure@$DIR/issue-99875.rs:14:11: 14:34]: Trait` is not satisfied
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--> $DIR/issue-99875.rs:14:11
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LL | takes(|_: Argument| -> Return { todo!() });
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| ----- ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Trait` is not implemented for closure `[closure@$DIR/issue-99875.rs:14:11: 14:34]`
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| |
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| required by a bound introduced by this call
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= help: the trait `Trait` is implemented for fn pointer `fn(Argument) -> Return`
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note: required by a bound in `takes`
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--> $DIR/issue-99875.rs:9:18
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LL | fn takes(_: impl Trait) {}
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| ^^^^^ required by this bound in `takes`
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error: aborting due to 2 previous errors
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For more information about this error, try `rustc --explain E0277`.
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