Move /src/test to /tests

tests/ui/impl-trait/impl-fn-predefined-lifetimes.rs

@@ -0,0 +1,15 @@
+#![feature(impl_trait_in_fn_trait_return)]
+use std::fmt::Debug;
+
+fn a<'a>() -> impl Fn(&'a u8) -> (impl Debug + '_) {
+    //~^ ERROR cannot resolve opaque type
+
+    |x| x
+    //~^ ERROR concrete type differs from previous defining opaque type use
+}
+
+fn _b<'a>() -> impl Fn(&'a u8) -> (impl Debug + 'a) {
+    a()
+}
+
+fn main() {}