error[E0623]: lifetime mismatch
  --> $DIR/ex2c-push-inference-variable.rs:7:12
   |
LL | fn foo<'a, 'b, 'c>(x: &'a mut Vec<Ref<'b, i32>>, y: Ref<'c, i32>) {
   |                                   ------------      ------------ these two types are declared with different lifetimes...
LL |     let z = Ref { data: y.data };
LL |     x.push(z);
   |            ^ ...but data from `y` flows into `x` here

error: aborting due to previous error