unit test for new error help.

Author: pnkfelix

src/test/compile-fail/suggest-path-instead-of-mod-dot-item.rs

@@ -0,0 +1,60 @@
+// Copyright 2015 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.
+
+// Beginners write `mod.item` when they should write `mod::item`.
+// This tests that we suggest the latter when we encounter the former.
+
+pub mod a {
+    pub const I: i32 = 1;
+
+    pub fn f() -> i32 { 2 }
+
+    pub mod b {
+        pub const J: i32 = 3;
+
+        pub fn g() -> i32 { 4 }
+    }
+}
+
+fn h1() -> i32 {
+    a.I
+        //~^ ERROR E0425
+        //~| HELP To reference an item from the `a` module, use `a::I`
+}
+
+fn h2() -> i32 {
+    a.g()
+        //~^ ERROR E0425
+        //~| HELP To call a function from the `a` module, use `a::g(..)`
+}
+
+fn h3() -> i32 {
+    a.b.J
+        //~^ ERROR E0425
+        //~| HELP To reference an item from the `a` module, use `a::b`
+}
+
+fn h4() -> i32 {
+    a::b.J
+        //~^ ERROR E0425
+        //~| HELP To reference an item from the `a::b` module, use `a::b::J`
+}
+
+fn h5() -> i32 {
+    a.b.f()
+        //~^ ERROR E0425
+        //~| HELP To reference an item from the `a` module, use `a::b`
+}
+
+fn h6() -> i32 {
+    a::b.f()
+        //~^ ERROR E0425
+        //~| HELP To call a function from the `a::b` module, use `a::b::f(..)`
+}