error[E0005]: refutable pattern in local binding: `T(_, _)` not covered
  --> $DIR/empty-never-array.rs:10:9
   |
LL |     let Helper::U(u) = Helper::T(t, []);
   |         ^^^^^^^^^^^^ pattern `T(_, _)` not covered

error: aborting due to previous error

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