associated-types-binding-to-type-defined-in-supertrait.rs

// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

// Test equality constraints in a where clause where the type being
// equated appears in a supertrait.

pub trait Vehicle {
    type Color;

    fn go(&self) {  }
}

pub trait Car : Vehicle {
    fn honk(&self) { }
}

///////////////////////////////////////////////////////////////////////////

struct Black;
struct ModelT;
impl Vehicle for ModelT { type Color = Black; }
impl Car for ModelT { }

///////////////////////////////////////////////////////////////////////////

struct Blue;
struct ModelU;
impl Vehicle for ModelU { type Color = Blue; }
impl Car for ModelU { }

///////////////////////////////////////////////////////////////////////////

fn black_car<C:Car<Color=Black>>(c: C) {
}

fn blue_car<C:Car<Color=Blue>>(c: C) {
}

fn a() { black_car(ModelT); }
fn b() { blue_car(ModelT); } //~ ERROR type mismatch
fn c() { black_car(ModelU); } //~ ERROR type mismatch
fn d() { blue_car(ModelU); }

pub fn main() { }