error[E0277]: the trait bound `fn(Argument) -> Return {function}: Trait` is not satisfied --> $DIR/issue-99875.rs:12:11 | LL | takes(function); | ----- ^^^^^^^^ the trait `Trait` is not implemented for fn item `fn(Argument) -> Return {function}` | | | required by a bound introduced by this call | note: required by a bound in `takes` --> $DIR/issue-99875.rs:9:18 | LL | fn takes(_: impl Trait) {} | ^^^^^ required by this bound in `takes` help: the trait `Trait` is implemented for fn pointer `fn(Argument) -> Return`, try casting using `as` | LL | takes(function as fn(Argument) -> Return); | +++++++++++++++++++++++++ error[E0277]: the trait bound `[closure@$DIR/issue-99875.rs:14:11: 14:34]: Trait` is not satisfied --> $DIR/issue-99875.rs:14:11 | LL | takes(|_: Argument| -> Return { todo!() }); | ----- ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Trait` is not implemented for closure `[closure@$DIR/issue-99875.rs:14:11: 14:34]` | | | required by a bound introduced by this call | = help: the trait `Trait` is implemented for fn pointer `fn(Argument) -> Return` note: required by a bound in `takes` --> $DIR/issue-99875.rs:9:18 | LL | fn takes(_: impl Trait) {} | ^^^^^ required by this bound in `takes` error: aborting due to 2 previous errors For more information about this error, try `rustc --explain E0277`.