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+// edition:2018
+
+trait Trait<'a, 'b> {}
+impl<T> Trait<'_, '_> for T {}
+
+// `Ordinary<'a> <: Ordinary<'b>` if `'a: 'b`, as with most types.
+//
+// I am purposefully avoiding the terms co- and contra-variant because
+// their application to regions depends on how you interpreted Rust
+// regions. -nikomatsakis
+struct Ordinary<'a>(&'a u8);
+
+// Here we get an error because none of our choices (either `'d` nor `'e`) are outlived
+// by both `'a` and `'b`.
+
+fn upper_bounds<'a, 'b, 'c, 'd, 'e>(a: Ordinary<'a>, b: Ordinary<'b>) -> impl Trait<'d, 'e>
+where
+ 'a: 'e,
+ 'b: 'd,
+{
+ // Hidden type `Ordinary<'0>` with constraints:
+ //
+ // ```
+ // 'a: '0
+ // 'b: '0
+ // 'a in ['d, 'e]
+ // ```
+ if condition() { a } else { b }
+ //~^ ERROR hidden type for `impl Trait<'d, 'e>` captures lifetime that does not appear in bounds
+}
+
+fn condition() -> bool {
+ true
+}
+
+fn main() {}