Update tests to demonstrate 2015 behaviour.

Adds a test to demonstrate behaviour of suggestions in the
2015 edition.

src/test/ui/rust-2018/local-path-suggestions-2015.rs

@@ -0,0 +1,36 @@
+// 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.
+
+// aux-build:baz.rs
+// compile-flags:--extern baz
+// edition:2015
+
+// This test exists to demonstrate the behaviour of the import suggestions
+// from the `local-path-suggestions-2018.rs` test when not using the 2018 edition.
+
+extern crate baz as aux_baz;
+
+mod foo {
+    pub type Bar = u32;
+}
+
+mod baz {
+    use foo::Bar;
+
+    fn baz() {
+        let x: Bar = 22;
+    }
+}
+
+use foo::Bar;
+
+use foobar::Baz;
+
+fn main() { }

src/test/ui/rust-2018/local-path-suggestions-2015.stderr

@@ -0,0 +1,9 @@
+error[E0432]: unresolved import `foobar`
+  --> $DIR/local-path-suggestions-2015.rs:34:5
+   |
+LL | use foobar::Baz;
+   |     ^^^^^^ Did you mean `aux_baz::foobar`?
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0432`.

src/test/ui/rust-2018/local-path-suggestions-2018.rs

@@ -13,7 +13,7 @@
 // edition:2018
 
 mod foo {
-    type Bar = u32;
+    pub type Bar = u32;
 }
 
 mod baz {

src/test/ui/rust-2018/local-path-suggestions-2018.stderr

@@ -1,17 +1,17 @@
 error[E0432]: unresolved import `foo`
-  --> $DIR/local-path-suggestions.rs:20:9
+  --> $DIR/local-path-suggestions-2018.rs:20:9
    |
 LL |     use foo::Bar;
    |         ^^^ Did you mean `crate::foo`?
 
 error[E0432]: unresolved import `foo`
-  --> $DIR/local-path-suggestions.rs:27:5
+  --> $DIR/local-path-suggestions-2018.rs:27:5
    |
 LL | use foo::Bar;
    |     ^^^ Did you mean `self::foo`?
 
 error[E0432]: unresolved import `foobar`
-  --> $DIR/local-path-suggestions.rs:29:5
+  --> $DIR/local-path-suggestions-2018.rs:29:5
    |
 LL | use foobar::Baz;
    |     ^^^^^^ Did you mean `baz::foobar`?