| // Copyright 2017 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. |
| |
| // Tests how we behave when the user attempts to mutate an immutable |
| // binding that was introduced by either `ref` or `ref mut` |
| // patterns. |
| // |
| // Such bindings cannot be made mutable via the mere addition of the |
| // `mut` keyword, and thus we want to check that the compiler does not |
| // suggest doing so. |
| |
| fn main() { |
| let (mut one_two, mut three_four) = ((1, 2), (3, 4)); |
| let &mut (ref a, ref mut b) = &mut one_two; |
| a = &three_four.0; |
| //~^ ERROR cannot assign twice to immutable variable `a` [E0384] |
| b = &mut three_four.1; |
| //~^ ERROR cannot assign twice to immutable variable `b` [E0384] |
| } |
