Error code E0697

A closure has been used as static.

Erroneous code example:

fn main() {
    static || {}; // used as `static`
}

Closures cannot be used as static. They "save" the environment, and as such a static closure would save only a static environment which would consist only of variables with a static lifetime. Given this it would be better to use a proper function. The easiest fix is to remove the static keyword.