Error code E0186

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:

#![allow(unused)]
fn main() {
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:

#![allow(unused)]
fn main() {
trait Foo {
    fn foo(&self);
}

struct Bar;

impl Foo for Bar {
    fn foo(&self) {} // ok!
}
}