error[E0005]: refutable pattern in local binding: `Bar` not covered
  --> $DIR/issue-31561.rs:18:9
   |
LL |     let Thing::Foo(y) = Thing::Foo(1);
   |         ^^^^^^^^^^^^^ pattern `Bar` not covered

error: aborting due to previous error

For more information about this error, try `rustc --explain E0005`.