src/test/ui/associated-types/associated-types-eq-3.rs

// Test equality constraints on associated types. Check we get type errors
// where we should.

pub trait Foo {
    type A;
    fn boo(&self) -> <Self as Foo>::A;
}

struct Bar;

impl Foo for isize {
    type A = usize;
    fn boo(&self) -> usize {
        42
    }
}

fn foo1<I: Foo<A=Bar>>(x: I) {
    let _: Bar = x.boo();
}

fn foo2<I: Foo>(x: I) {
    let _: Bar = x.boo();
    //~^ ERROR mismatched types
    //~| found associated type `<I as Foo>::A`
    //~| expected struct `Bar`, found associated type
    //~| expected struct `Bar`
}


pub fn baz(x: &dyn Foo<A=Bar>) {
    let _: Bar = x.boo();
}


pub fn main() {
    let a = 42;
    foo1(a);
    //~^ ERROR type mismatch resolving
    //~| expected struct `Bar`, found `usize`
    baz(&a);
    //~^ ERROR type mismatch resolving
    //~| expected struct `Bar`, found `usize`
}