item: Consider replaced items hidden.

[emilio]

Fixes #81

r? @nox

[fitzgen]

By modifying this test header, I get a similar error (using this PR and #85). Not sure if we want to put this off for another PR or not.

diff --git a/tests/headers/replaces_double.hpp b/tests/headers/replaces_double.hpp
index 1a78b0d..74d500b 100644
--- a/tests/headers/replaces_double.hpp
+++ b/tests/headers/replaces_double.hpp
@@ -7,14 +7,15 @@ struct Wrapper {
     };
     using Type = Wrapped;
 };

 template<typename T>
 class Rooted {
     using MaybeWrapped = typename Wrapper<T>::Type;
     MaybeWrapped ptr;
-
-    /**
-     * <div rustbindgen replaces="Rooted_MaybeWrapped"></div>
-     */
-    using MaybeWrapped_simple = T;
 };
+
+/**
+ * <div rustbindgen replaces="Rooted_MaybeWrapped"></div>
+ */
+template <typename T>
+using MaybeWrapped_simple = T;

Results in this error due to duplicate types:

error[E0428]: a type named `Rooted_MaybeWrapped` has already been defined in this module
  --> tests/expectations/replaces_double.rs:16:1
   |
12 | pub type Rooted_MaybeWrapped<T> = T;
   | ------------------------------------ previous definition of `Rooted_MaybeWrapped` here
...
16 | pub type Rooted_MaybeWrapped<T> = T;
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ already defined

error: aborting due to previous error

[fitzgen]

Nevermind: I think I failed to recompile.

[nox]

@bors-servo r+

[bors-servo]

📌 Commit c30320f has been approved by nox

[bors-servo]

⌛ Testing commit c30320f with merge b162e92...

[bors-servo]

☀️ Test successful - status-travis