## Keyboard shortcuts

Press `←` or `→` to navigate between chapters

Press `S` or `/` to search in the book

Press `?` to show this help

Press `Esc` to hide this help

# Error code E0750

A negative impl was made default impl.

Erroneous code example:

    #![feature(negative_impls)]
    #![feature(specialization)]
    trait MyTrait {
        type Foo;
    }

    default impl !MyTrait for u32 {} // error!
    fn main() {}

Negative impls cannot be default impls. A default impl supplies default values for the items within to be used by other impls, whereas a negative impl declares that there are no other impls. Combining it does not make sense.