Increase test coverage of use_nested_groups

Author: pietroalbini

src/test/run-pass/use-nested-groups.rs

@@ -24,12 +24,19 @@ mod a {
     }
 }
 
+// Test every possible part of the syntax
 use a::{B, d::{self, *, g::H}};
 
+// Test a more common use case
+use std::sync::{Arc, atomic::{AtomicBool, Ordering}};
+
 fn main() {
     let _: B;
     let _: E;
     let _: F;
     let _: H;
     let _: d::g::I;
+
+    let _: Arc<AtomicBool>;
+    let _: Ordering;
 }

src/test/ui/use-nested-groups-error.rs

@@ -0,0 +1,27 @@
+// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![feature(use_nested_groups)]
+
+mod a {
+    pub mod b1 {
+        pub enum C2 {}
+    }
+
+    pub enum B2 {}
+}
+
+use a::{b1::{C1, C2}, B2};
+//~^ ERROR unresolved import `a::b1::C1`
+
+fn main() {
+    let _: C2;
+    let _: B2;
+}

src/test/ui/use-nested-groups-error.stderr

@@ -0,0 +1,8 @@
+error[E0432]: unresolved import `a::b1::C1`
+  --> $DIR/use-nested-groups-error.rs:21:14
+   |
+21 | use a::{b1::{C1, C2}, B2};
+   |              ^^ no `C1` in `a::b1`. Did you mean to use `C2`?
+
+error: aborting due to previous error
+