// Nested impl-traits can impose different member constraints on the same region variable. // check-fail trait Cap<'a> {} impl Cap<'_> for T {} // Assuming the hidden type is `[&'_#15r u8; 1]`, we have two distinct member constraints: // - '_#15r member ['static, 'a, 'b] // from outer impl-trait // - '_#15r member ['static, 'a, 'b] // from inner impl-trait // To satisfy both we can choose 'a or 'b, so it's a failure due to ambiguity. fn fail_early_bound<'s, 'a, 'b>(a: &'s u8) -> impl IntoIterator + Cap<'b>> where 's: 'a, 's: 'b, { [a] //~^ E0700 //~| E0700 } // Same as the above but with late-bound regions. fn fail_late_bound<'s, 'a, 'b>( a: &'s u8, _: &'a &'s u8, _: &'b &'s u8, ) -> impl IntoIterator + Cap<'b>> { [a] //~^ E0700 //~| E0700 } fn main() {}