warning: value assigned to `a` is never read
  --> $DIR/liveness_unintentional_copy.rs:20:9
   |
LL |         a = s;
   |         ^
   |
   = help: maybe it is overwritten before being read?
note: the lint level is defined here
  --> $DIR/liveness_unintentional_copy.rs:4:9
   |
LL | #![warn(unused)]
   |         ^^^^^^
   = note: `#[warn(unused_assignments)]` implied by `#[warn(unused)]`

warning: unused variable: `a`
  --> $DIR/liveness_unintentional_copy.rs:20:9
   |
LL |         a = s;
   |         ^
   |
   = help: did you mean to capture by reference instead?
   = note: `#[warn(unused_variables)]` implied by `#[warn(unused)]`

warning: unused variable: `a`
  --> $DIR/liveness_unintentional_copy.rs:36:9
   |
LL |         a += x;
   |         ^
   |
   = help: did you mean to capture by reference instead?

warning: 3 warnings emitted