rust/src/test/compile-fail/trait-impl-method-mismatch.rs

// Copyright 2012 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.

trait Mumbo {
    pure fn jumbo(&self, x: @uint) -> uint;
    fn jambo(&self, x: @const uint) -> uint;
    fn jbmbo(&self) -> @uint;
}

impl Mumbo for uint {
    // Cannot have a larger effect than the trait:
    fn jumbo(&self, x: @uint) { *self + *x; }
    //~^ ERROR expected pure fn but found impure fn

    // Cannot accept a narrower range of parameters:
    fn jambo(&self, x: @uint) { *self + *x; }
    //~^ ERROR values differ in mutability

    // Cannot return a wider range of values:
    fn jbmbo(&self) -> @const uint { @const 0 }
    //~^ ERROR values differ in mutability
}

fn main() {}