src/test/ui/reassign-ref-mut.rs

   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
   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 }