error[E0495]: cannot infer an appropriate lifetime for lifetime parameter `'a` due to conflicting requirements
  --> $DIR/ex2d-push-inference-variable-2.rs:17:13
   |
17 |     let b = Ref { data: y.data };
   |             ^^^
   |
note: first, the lifetime cannot outlive the lifetime 'c as defined on the body at 15:66...
  --> $DIR/ex2d-push-inference-variable-2.rs:15:67
   |
15 |   fn foo<'a, 'b, 'c>(x: &'a mut Vec<Ref<'b, i32>>, y: Ref<'c, i32>) {
   |  ___________________________________________________________________^ starting here...
16 | |     let a: &mut Vec<Ref<i32>> = x;
17 | |     let b = Ref { data: y.data };
18 | |     a.push(b);
19 | | }
   | |_^ ...ending here
note: ...so that reference does not outlive borrowed content
  --> $DIR/ex2d-push-inference-variable-2.rs:17:25
   |
17 |     let b = Ref { data: y.data };
   |                         ^^^^^^
note: but, the lifetime must be valid for the lifetime 'b as defined on the body at 15:66...
  --> $DIR/ex2d-push-inference-variable-2.rs:15:67
   |
15 |   fn foo<'a, 'b, 'c>(x: &'a mut Vec<Ref<'b, i32>>, y: Ref<'c, i32>) {
   |  ___________________________________________________________________^ starting here...
16 | |     let a: &mut Vec<Ref<i32>> = x;
17 | |     let b = Ref { data: y.data };
18 | |     a.push(b);
19 | | }
   | |_^ ...ending here
note: ...so that expression is assignable (expected &mut std::vec::Vec<Ref<'_, i32>>, found &mut std::vec::Vec<Ref<'b, i32>>)
  --> $DIR/ex2d-push-inference-variable-2.rs:16:33
   |
16 |     let a: &mut Vec<Ref<i32>> = x;
   |                                 ^

error: aborting due to previous error