warning: value assigned to `a` is never read
  --> $DIR/warn-unused-duplication.rs:9:6
   |
LL |     (a, a) = (0, 1);
   |      ^
   |
note: the lint level is defined here
  --> $DIR/warn-unused-duplication.rs:3:9
   |
LL | #![warn(unused_assignments)]
   |         ^^^^^^^^^^^^^^^^^^
   = help: maybe it is overwritten before being read?

warning: 1 warning emitted