warning: unused variable: `a`
  --> $DIR/liveness-derive.rs:15:13
   |
LL |         let a = 0;
   |             ^ help: if this is intentional, prefix it with an underscore: `_a`
   |
note: the lint level is defined here
  --> $DIR/liveness-derive.rs:6:9
   |
LL | #![warn(unused)]
   |         ^^^^^^
   = note: `#[warn(unused_variables)]` implied by `#[warn(unused)]`

warning: unused variable: `b`
  --> $DIR/liveness-derive.rs:20:13
   |
LL |         let b = 16;
   |             ^ help: if this is intentional, prefix it with an underscore: `_b`

warning: 2 warnings emitted