| #### Note: this error code is no longer emitted by the compiler. | |
| You tried to supply a type which doesn't implement some trait in a location | |
| which expected that trait. This error typically occurs when working with | |
| `Fn`-based types. Erroneous code example: | |
| ```compile_fail | |
| fn foo<F: Fn(usize)>(x: F) { } | |
| fn main() { | |
| // type mismatch: ... implements the trait `core::ops::Fn<(String,)>`, | |
| // but the trait `core::ops::Fn<(usize,)>` is required | |
| // [E0281] | |
| foo(|y: String| { }); | |
| } | |
| ``` | |
| The issue in this case is that `foo` is defined as accepting a `Fn` with one | |
| argument of type `String`, but the closure we attempted to pass to it requires | |
| one arguments of type `usize`. |