rust/tests/ui/return-disjoint-regions.rs

// See https://github.com/rust-lang/rust/pull/67911#issuecomment-576023915
fn f<'a, 'b>(x: i32) -> (&'a i32, &'b i32) {
    let y = &x;
    (y, y) //~ ERROR cannot return
}

fn main() {}
Use an 'approximate' universal upper bound when reporting region errors Fixes #67765 When reporting errors during MIR region inference, we sometimes use `universal_upper_bound` to obtain a named universal region that we can display to the user. However, this is not always possible - in a case like `fn foo<'a, 'b>() { .. }`, the only upper bound for a region containing `'a` and `'b` is `'static`. When displaying diagnostics, it's usually better to display some named region (even if there are multiple involved) rather than fall back to a generic error involving `'static`. This commit adds a new `approx_universal_upper_bound` method, which uses the lowest-numbered universal region if the only alternative is to return `'static`. 2020-06-27 17:54:56 +00:00			`// See https://github.com/rust-lang/rust/pull/67911#issuecomment-576023915`
			`fn f<'a, 'b>(x: i32) -> (&'a i32, &'b i32) {`
			`let y = &x;`
			`(y, y) //~ ERROR cannot return`
			`}`

			`fn main() {}`