rust/src/test/compile-fail/issue-2951.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.

fn foo<T, U>(x: T, y: U) {
    let mut xx = x;
    xx = y;
    //~^  ERROR mismatched types
    //~| expected type `T`
    //~| found type `U`
    //~| expected type parameter, found a different type parameter
}

fn main() {
}