1 // Tests how we behave when the user attempts to mutate an immutable
2 // binding that was introduced by either `ref` or `ref mut`
3 // patterns.
4 //
5 // Such bindings cannot be made mutable via the mere addition of the
6 // `mut` keyword, and thus we want to check that the compiler does not
7 // suggest doing so.
8
main()9 fn main() {
10 let (mut one_two, mut three_four) = ((1, 2), (3, 4));
11 let &mut (ref a, ref mut b) = &mut one_two;
12 a = &three_four.0;
13 //~^ ERROR cannot assign twice to immutable variable `a` [E0384]
14 b = &mut three_four.1;
15 //~^ ERROR cannot assign twice to immutable variable `b` [E0384]
16 }
17