error: unused variable: `a`
  --> $DIR/issue-22599.rs:18:19
   |
LL |     v = match 0 { a => 0 }; //~ ERROR: unused variable: `a`
   |                   ^ help: consider using `_a` instead
   |
note: lint level defined here
  --> $DIR/issue-22599.rs:11:9
   |
LL | #![deny(unused_variables)]
   |         ^^^^^^^^^^^^^^^^

error: aborting due to previous error