error[E0307]: invalid `self` type: &SomeType
  --> $DIR/issue-27522.rs:16:22
   |
LL |     fn handler(self: &SomeType); //~ ERROR invalid `self` type
   |                      ^^^^^^^^^
   |
   = note: type must be `Self` or a type that dereferences to it`
   = help: consider changing to `self`, `&self`, `&mut self`, or `self: Box<Self>`

error: aborting due to previous error

If you want more information on this error, try using "rustc --explain E0307"