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# Error code E0379

A trait method was declared const.

Erroneous code example:

    #![allow(unused)]
    fn main() {
    trait Foo {
        const fn bar() -> u32; // error!
    }

    impl Foo for () {
        const fn bar() -> u32 { 0 } // error!
    }
    }

Trait methods cannot be declared `const` by design. For more information, see RFC 911.