error[E0521]: borrowed data escapes outside of function
  --> $DIR/regions-bounded-method-type-parameters-trait-bound.rs:20:5
   |
LL | fn caller2<'a,'b,F:Foo<'a>>(a: Inv<'a>, b: Inv<'b>, f: F) {
   |                             -           - `b` is a reference that is only valid in the function body
   |                             |
   |                             `a` declared here, outside of the function body
LL |     // Here the value provided for 'y is 'b, and hence 'b:'a does not hold.
LL |     f.method(b);
   |     ^^^^^^^^^^^ `b` escapes the function body here
   |
   = help: consider adding the following bound: `'b: 'a`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0521`.