E4010

pub is not allowed on default implementation for traits. The default implementation has the same visibility as the trait itself.

Erroneous Example

pub(open) trait Stringer {
  stringify(Self) -> String = _
}

pub impl Stringer with stringify(_self) { "hey" }

In the example above, the pub keyword is used on the default implementation of the Stringer trait, which is not allowed.

Suggestion

Remove the pub keyword so that the default implementation has the same visibility as the trait itself:

pub(open) trait Stringer {
  stringify(Self) -> String = _
}

impl Stringer with stringify(_self) { "hey" }