error: rustc_outlives
  --> $DIR/nested-regions.rs:4:1
   |
LL | / struct Foo<'a, 'b, T> {
LL | |     x: &'a &'b T
LL | | }
   | |_^
   |
   = note: 'b: 'a
   = note: T: 'a
   = note: T: 'b

error: aborting due to previous error