error[E0495]: cannot infer an appropriate lifetime for lifetime parameter `'a` due to conflicting requirements
  --> $DIR/ex2c-push-inference-variable.rs:16:13
   |
16 |     let z = Ref { data: y.data };
   |             ^^^
   |
note: first, the lifetime cannot outlive the lifetime 'c as defined on the body at 15:66...
  --> $DIR/ex2c-push-inference-variable.rs:15:67
   |
15 |   fn foo<'a, 'b, 'c>(x: &'a mut Vec<Ref<'b, i32>>, y: Ref<'c, i32>) {
   |  ___________________________________________________________________^ starting here...
16 | |     let z = Ref { data: y.data };
17 | |     x.push(z);
18 | | }
   | |_^ ...ending here
note: ...so that reference does not outlive borrowed content
  --> $DIR/ex2c-push-inference-variable.rs:16:25
   |
16 |     let z = Ref { data: y.data };
   |                         ^^^^^^
note: but, the lifetime must be valid for the lifetime 'b as defined on the body at 15:66...
  --> $DIR/ex2c-push-inference-variable.rs:15:67
   |
15 |   fn foo<'a, 'b, 'c>(x: &'a mut Vec<Ref<'b, i32>>, y: Ref<'c, i32>) {
   |  ___________________________________________________________________^ starting here...
16 | |     let z = Ref { data: y.data };
17 | |     x.push(z);
18 | | }
   | |_^ ...ending here
note: ...so that expression is assignable (expected Ref<'b, i32>, found Ref<'_, i32>)
  --> $DIR/ex2c-push-inference-variable.rs:17:12
   |
17 |     x.push(z);
   |            ^

error: aborting due to previous error