error[E0599]: no method named `foo` found for struct `A` in the current scope
  --> $DIR/point-at-arbitrary-self-type-trait-method.rs:9:7
   |
LL | trait B { fn foo(self: Box<Self>); }
   |              ---       --------- the method might not be found because of this arbitrary self type
   |              |
   |              the method is available for `std::boxed::Box<A>` here
LL | struct A;
   | --------- method `foo` not found for this
...
LL |     A.foo()
   |       ^^^ method not found in `A`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0599`.