error[E0309]: the parameter type `T` may not live long enough
  --> $DIR/wf-impl-associated-type-region.rs:10:5
   |
LL | impl<'a, T> Foo<'a> for T {
   |      -- the parameter type `T` must be valid for the lifetime `'a` as defined here...
LL |     type Bar = &'a T;
   |     ^^^^^^^^ ...so that the reference type `&'a T` does not outlive the data it points at
   |
help: consider adding an explicit lifetime bound
   |
LL | impl<'a, T: 'a> Foo<'a> for T {
   |           ++++

error: aborting due to 1 previous error

For more information about this error, try `rustc --explain E0309`.