error: methods called `as_*` usually take `self` by reference or `self` by mutable reference
  --> $DIR/def_id_nocore.rs:27:19
   |
LL |     pub fn as_ref(self) -> &'static str {
   |                   ^^^^
   |
   = help: consider choosing a less ambiguous name
   = note: `-D clippy::wrong-self-convention` implied by `-D warnings`
   = help: to override `-D warnings` add `#[allow(clippy::wrong_self_convention)]`

error: aborting due to 1 previous error