Do not suggest adjusting trait signature on type mismatch

compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs

@@ -3959,6 +3959,10 @@ fn hint_missing_borrow<'tcx>(
     found_node: Node<'_>,
     err: &mut Diagnostic,
 ) {
+    if matches!(found_node, Node::TraitItem(..)) {
+        return;
+    }
+
     let found_args = match found.kind() {
         ty::FnPtr(f) => infcx.instantiate_binder_with_placeholders(*f).inputs().iter(),
         kind => {

tests/ui/typeck/mismatched-map-under-self.stderr

@@ -30,11 +30,6 @@ LL |         self.map(Insertable::values).unwrap_or_default()
               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 adjusting the signature so it does not borrow its argument
-   |
-LL -     fn values(&self) -> Self::Values;
-LL +     fn values(self) -> Self::Values;
-   |
 
 error: aborting due to 2 previous errors