error[E0623]: lifetime mismatch
  --> $DIR/ex3-both-anon-regions-one-is-struct-4.rs:4:11
   |
LL | fn foo(mut y: Ref, x: &u32) {
   |               ---     ---- these two types are declared with different lifetimes...
LL |     y.b = x;
   |           ^ ...but data from `x` flows into `y` here

error: aborting due to previous error

For more information about this error, try `rustc --explain E0623`.