rust/tests/ui/regions/regions-creating-enums.rs

34 lines
753 B
Rust

enum Ast<'a> {
Num(usize),
Add(&'a Ast<'a>, &'a Ast<'a>)
}
fn build() {
let x = Ast::Num(3);
let y = Ast::Num(4);
let z = Ast::Add(&x, &y);
compute(&z);
}
fn compute(x: &Ast) -> usize {
match *x {
Ast::Num(x) => { x }
Ast::Add(x, y) => { compute(x) + compute(y) }
}
}
fn map_nums<'a,'b, F>(x: &Ast, f: &mut F) -> &'a Ast<'b> where F: FnMut(usize) -> usize {
match *x {
Ast::Num(x) => {
return &Ast::Num((*f)(x)); //~ ERROR cannot return reference to temporary value
}
Ast::Add(x, y) => {
let m_x = map_nums(x, f);
let m_y = map_nums(y, f);
return &Ast::Add(m_x, m_y); //~ ERROR cannot return reference to temporary value
}
}
}
fn main() {}