warning: value captured by `a` is never read
  --> $DIR/liveness.rs:24:9
   |
LL |         a = 1;
   |         ^
   |
   = help: did you mean to capture by reference instead?
note: the lint level is defined here
  --> $DIR/liveness.rs:5:9
   |
LL | #![warn(unused)]
   |         ^^^^^^
   = note: `#[warn(unused_assignments)]` implied by `#[warn(unused)]`

warning: unused variable: `a`
  --> $DIR/liveness.rs:33:9
   |
LL |         a += 1;
   |         ^
   |
   = help: did you mean to capture by reference instead?
   = note: `#[warn(unused_variables)]` implied by `#[warn(unused)]`

warning: value assigned to `a` is never read
  --> $DIR/liveness.rs:53:9
   |
LL |         a += 1;
   |         ^
   |
   = help: maybe it is overwritten before being read?

warning: value assigned to `a` is never read
  --> $DIR/liveness.rs:77:13
   |
LL |             a = Some("d1");
   |             ^
   |
   = help: maybe it is overwritten before being read?

warning: value assigned to `b` is never read
  --> $DIR/liveness.rs:85:13
   |
LL |             b = Some("e1");
   |             ^
   |
   = help: maybe it is overwritten before being read?

warning: value assigned to `b` is never read
  --> $DIR/liveness.rs:87:13
   |
LL |             b = Some("e2");
   |             ^
   |
   = help: maybe it is overwritten before being read?

warning: unused variable: `b`
  --> $DIR/liveness.rs:85:13
   |
LL |             b = Some("e1");
   |             ^
   |
   = help: did you mean to capture by reference instead?

warning: 7 warnings emitted