#![deny(single_use_lifetimes)] pub enum Data<'a> { Borrowed(&'a str), Owned(String), } impl<'a> Data<'a> { pub fn get<'b: 'a>(&'b self) -> &'a str { //~^ ERROR lifetime parameter `'b` only used once match &self { Self::Borrowed(val) => val, Self::Owned(val) => &val, } } } fn main() {}