error: called `map_or(Err(_), Ok)` on an `Option` value
  --> $DIR/option_map_or_err_ok.rs:5:13
   |
LL |     let _ = x.map_or(Err("a"), Ok);
   |             ^^^^^^^^^^^^^^^^^^^^^^ help: try using `ok_or` instead: `x.ok_or("a")`
   |
   = note: `-D clippy::option-map-or-err-ok` implied by `-D warnings`
   = help: to override `-D warnings` add `#[allow(clippy::option_map_or_err_ok)]`

error: aborting due to 1 previous error