Update impl trait tests and add failing run-pass region test

Author: cramertj

src/test/compile-fail/impl-trait/lifetimes.rs

@@ -13,28 +13,20 @@
 // Helper creating a fake borrow, captured by the impl Trait.
 fn borrow<'a, T>(_: &'a mut T) -> impl Copy { () }
 
-fn stack() -> impl Copy {
-    //~^ ERROR only named lifetimes are allowed in `impl Trait`
-    let x = 0;
-    &x
-}
-
 fn late_bound(x: &i32) -> impl Copy {
-    //~^ ERROR only named lifetimes are allowed in `impl Trait`
     x
+    //~^ cannot infer an appropriate lifetime
 }
 
-// FIXME(#34511) Should work but doesn't at the moment,
-// region-checking needs an overhault to support this.
 fn early_bound<'a>(x: &'a i32) -> impl Copy {
-    //~^ ERROR only named lifetimes are allowed in `impl Trait`
     x
+    //~^ cannot infer an appropriate lifetime
 }
 
 fn ambiguous<'a, 'b>(x: &'a [u32], y: &'b [u32]) -> impl Iterator<Item=u32> {
-    //~^ ERROR only named lifetimes are allowed in `impl Trait`
     if x.len() < y.len() {
         x.iter().cloned()
+        //~^ cannot infer an appropriate lifetime
     } else {
         y.iter().cloned()
     }

src/test/compile-fail/impl-trait/more_lifetimes.rs

@@ -12,27 +12,20 @@
 
 use std::fmt::Debug;
 
-fn foo<'a>(x: &'a i32) -> impl Debug + 'a {
-    x
-}
-
-fn foo_not_static() -> impl Debug + 'static {
-    let mut x = 5;
-    x += 5;
-    foo(&x)
-    //~^ ERROR `x` does not live long enough
-}
-
 trait Any {}
 impl<T> Any for T {}
 
 // Check that type parameters are captured and not considered 'static
 fn whatever<T>(x: T) -> impl Any + 'static {
-    x
     //~^ ERROR the parameter type `T` may not live long enough
+    x
 }
 
 fn move_lifetime_into_fn<'a, 'b>(x: &'a u32, y: &'b u32) -> impl Fn(&'a u32) {
+    //~^ ERROR lifetime mismatch
+    //~^^ ERROR only named lifetimes are allowed in `impl Trait`, but `'b` was found
+    //~^^^ ERROR only named lifetimes are allowed in `impl Trait`, but `'b` was found
+    // TODO^ remove the above duplicate errors
     move |_| println!("{}", y)
 }
 

src/test/run-pass/impl-trait/lifetimes.rs

@@ -9,6 +9,7 @@
 // except according to those terms.
 
 #![feature(conservative_impl_trait)]
+#![allow(warnings)]
 
 use std::fmt::Debug;
 
@@ -35,4 +36,18 @@ fn mixed_lifetimes<'a>() -> impl for<'b: 'a> Fn(&'b u32) { |_| () }
 
 fn mixed_as_static() -> impl Fn(&'static u32) { mixed_lifetimes() }
 
+trait MultiRegion<'a, 'b> {}
+struct MultiRegionStruct<'a, 'b>(&'a u32, &'b u32);
+impl<'a, 'b> MultiRegion<'a, 'b> for MultiRegionStruct<'a, 'b> {}
+
+fn finds_least_region<'a: 'b, 'b>(x: &'a u32, y: &'b u32) -> impl MultiRegion<'a, 'b>
+{
+    MultiRegionStruct(x, y)
+}
+
+fn explicit_bound<'a: 'b, 'b>(x: &'a u32, y: &'b u32) -> impl MultiRegion<'a, 'b> + 'b
+{
+    MultiRegionStruct(x, y)
+}
+
 fn main() {}