[rustc.git] / compiler / rustc_error_codes / src / error_codes / E0186.md

An associated function for a trait was defined to be a method (i.e., to take a
`self` parameter), but an implementation of the trait declared the same function
to be static.

Erroneous code example:

```compile_fail,E0186
trait Foo {
    fn foo(&self);
}

struct Bar;

impl Foo for Bar {
    // error, method `foo` has a `&self` declaration in the trait, but not in
    // the impl
    fn foo() {}
}
```

When a type implements a trait's associated function, it has to use the same
signature. So in this case, since `Foo::foo` takes `self` as argument and
does not return anything, its implementation on `Bar` should be the same:

```
trait Foo {
    fn foo(&self);
}

struct Bar;

impl Foo for Bar {
    fn foo(&self) {} // ok!
}
```
Commit	Line	Data
60c5eb7d XL	1	An associated function for a trait was defined to be a method (i.e., to take a
	2	`self` parameter), but an implementation of the trait declared the same function
	3	to be static.
	4
dfeec247	5	Erroneous code example:
60c5eb7d XL	6
	7	```compile_fail,E0186
	8	trait Foo {
	9	fn foo(&self);
	10	}
	11
	12	struct Bar;
	13
	14	impl Foo for Bar {
	15	// error, method `foo` has a `&self` declaration in the trait, but not in
	16	// the impl
	17	fn foo() {}
	18	}
	19	```
dfeec247 XL	20
	21	When a type implements a trait's associated function, it has to use the same
	22	signature. So in this case, since `Foo::foo` takes `self` as argument and
	23	does not return anything, its implementation on `Bar` should be the same:
	24
	25	```
	26	trait Foo {
	27	fn foo(&self);
	28	}
	29
	30	struct Bar;
	31
	32	impl Foo for Bar {
	33	fn foo(&self) {} // ok!
	34	}
	35	```