error[E0658]: `R` cannot be used as the type of `self` without the `arbitrary_self_types` feature
  --> $DIR/arbitrary-self-from-method-substs.rs:8:43
   |
LL |     fn get<R: Deref<Target = Self>>(self: R) -> u32 {
   |                                           ^
   |
   = note: see issue #44874 <https://github.com/rust-lang/rust/issues/44874> for more information
   = help: add `#![feature(arbitrary_self_types)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
   = help: consider changing to `self`, `&self`, `&mut self`, `self: Box<Self>`, `self: Rc<Self>`, `self: Arc<Self>`, or `self: Pin<P>` (where P is one of the previous types except `Self`)

ERROR rustc_hir_typeck::method::confirm Foo was a subtype of &Foo but now is not?
error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0658`.