rust-clippy/tests/ui/missing_trait_methods.rs

#![allow(unused, clippy::needless_lifetimes)]
#![warn(clippy::missing_trait_methods)]

trait A {
    fn provided() {}
}

trait B {
    fn required();

    fn a(_: usize) -> usize {
        1
    }

    fn b<'a, T: AsRef<[u8]>>(a: &'a T) -> &'a [u8] {
        a.as_ref()
    }
}

struct Partial;

impl A for Partial {}
//~^ ERROR: missing trait method provided by default: `provided`

impl B for Partial {
    //~^ ERROR: missing trait method provided by default: `b`
    fn required() {}

    fn a(_: usize) -> usize {
        2
    }
}

struct Complete;

impl A for Complete {
    fn provided() {}
}

impl B for Complete {
    fn required() {}

    fn a(_: usize) -> usize {
        2
    }

    fn b<T: AsRef<[u8]>>(a: &T) -> &[u8] {
        a.as_ref()
    }
}

trait MissingMultiple {
    fn one() {}
    fn two() {}
    fn three() {}
}

impl MissingMultiple for Partial {}

fn main() {}