error: lifetime may not live long enough --> $DIR/regions-creating-enums4.rs:7:5 | LL | fn mk_add_bad2<'a,'b>(x: &'a Ast<'a>, y: &'a Ast<'a>, z: &Ast) -> Ast<'b> { | -- -- lifetime `'b` defined here | | | lifetime `'a` defined here LL | Ast::Add(x, y) | ^^^^^^^^^^^^^^ function was supposed to return data with lifetime `'b` but it is returning data with lifetime `'a` | = help: consider adding the following bound: `'a: 'b` error: aborting due to 1 previous error