error: called `.err().expect()` on a `Result` value
  --> $DIR/err_expect.rs:10:16
   |
LL |     test_debug.err().expect("Testing debug type");
   |                ^^^^^^^^^^^^ help: try: `expect_err`
   |
   = note: `-D clippy::err-expect` implied by `-D warnings`

error: aborting due to previous error