An attempted implementation of a trait method has the wrong number of type or const parameters.
Erroneous code example:
trait Foo { fn foo<T: Default>(x: T) -> Self; } struct Bar; // error: method `foo` has 0 type parameters but its trait declaration has 1 // type parameter impl Foo for Bar { fn foo(x: bool) -> Self { Bar } }
For example, the Foo
trait has a method foo
with a type parameter T
, but the implementation of foo
for the type Bar
is missing this parameter. To fix this error, they must have the same type parameters:
trait Foo { fn foo<T: Default>(x: T) -> Self; } struct Bar; impl Foo for Bar { fn foo<T: Default>(x: T) -> Self { // ok! Bar } }