Fix leaking trait imports across modules

Turns out the pass in resolve was a little too eager to travel back up the
hierarchy chain when looking for trait candidates.

Closes #10465

src/librustc/middle/resolve.rs

@@ -5498,11 +5498,10 @@ fn search_for_traits_containing_method(&mut self, name: Ident)
 
                 // Move to the next parent.
                 match search_module.parent_link {
-                    NoParentLink => {
+                    NoParentLink | ModuleParentLink(..) => {
                         // Done.
                         break;
                     }
-                    ModuleParentLink(parent_module, _) |
                     BlockParentLink(parent_module, _) => {
                         search_module = parent_module;
                     }

src/test/compile-fail/issue-10465.rs

@@ -0,0 +1,33 @@
+// Copyright 2014 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.
+
+pub mod a {
+    pub trait A {
+        fn foo(&self);
+    }
+
+}
+pub mod b {
+    use a::A;
+
+    pub struct B;
+    impl A for B { fn foo(&self) {} }
+
+    pub mod c {
+        use b::B;
+
+        fn foo(b: &B) {
+            b.foo(); //~ ERROR: does not implement any method in scope named
+        }
+    }
+
+}
+
+fn main() {}