error[E0053]: method `values` has an incompatible type for trait
  --> $DIR/mismatched-map-under-self.rs:10:15
   |
LL |     fn values(self) -> Self::Values {
   |               ^^^^
   |               |
   |               expected `&Option<T>`, found `Option<T>`
   |               help: change the self-receiver type to match the trait: `&self`
   |
note: type in trait
  --> $DIR/mismatched-map-under-self.rs:4:15
   |
LL |     fn values(&self) -> Self::Values;
   |               ^^^^^
   = note: expected signature `fn(&Option<_>)`
              found signature `fn(Option<_>)`

error[E0631]: type mismatch in function arguments
  --> $DIR/mismatched-map-under-self.rs:12:18
   |
LL |     fn values(&self) -> Self::Values;
   |     --------------------------------- found signature defined here
...
LL |         self.map(Insertable::values).unwrap_or_default()
   |              --- ^^^^^^^^^^^^^^^^^^ expected due to this
   |              |
   |              required by a bound introduced by this call
   |
   = note: expected function signature `fn(T) -> _`
              found function signature `for<'a> fn(&'a _) -> _`
note: required by a bound in `Option::<T>::map`
  --> $SRC_DIR/core/src/option.rs:LL:COL
help: consider wrapping the function in a closure
   |
LL |         self.map(|arg0: T| Insertable::values(&arg0)).unwrap_or_default()
   |                  +++++++++                   +++++++

error: aborting due to 2 previous errors

Some errors have detailed explanations: E0053, E0631.
For more information about an error, try `rustc --explain E0053`.