#![deny(single_use_lifetimes)] #![allow(dead_code)] #![allow(unused_variables)] // Test that we DO warn when lifetime name is used only // once in a fn argument. struct Foo { a: for<'a> fn(&'a u32), //~ ERROR `'a` only used once b: for<'a> fn(&'a u32, &'a u32), // OK, used twice. c: for<'a> fn(&'a u32) -> &'a u32, // OK, used twice. d: for<'a> fn() -> &'a u32, // OK, used only in return type. //~^ ERROR return type references lifetime `'a`, which is not constrained by the fn input types } fn main() { }