diff --git a/gen/write.rs b/gen/write.rs
index f456e18..19762cc 100644
--- a/gen/write.rs
+++ b/gen/write.rs
@@ -889,32 +889,21 @@
     }
 }
 
+// Only called for legal referent types of unique_ptr and element types of
+// std::vector and Vec.
 fn to_typename(namespace: &Namespace, ty: &Type) -> String {
     match ty {
         Type::Ident(ident) => {
-            let mut inner = String::new();
-            // Do not apply namespace to built-in type
-            let is_user_type = Atom::from(ident).is_none();
-            if is_user_type {
-                for name in namespace {
-                    inner += name;
-                    inner += "::";
-                }
+            let mut path = String::new();
+            for name in namespace {
+                path += name;
+                path += "::";
             }
-            if let Some(ti) = Atom::from(ident) {
-                inner += ti.to_cxx();
-            } else {
-                inner += &ident.to_string();
-            };
-            inner
-        }
-        Type::RustBox(ptr) => format!("rust_box<{}>", to_typename(namespace, &ptr.inner)),
-        Type::RustVec(ptr) => format!("rust_vec<{}>", to_typename(namespace, &ptr.inner)),
-        Type::UniquePtr(ptr) => {
-            format!("::std::unique_ptr<{}>", to_typename(namespace, &ptr.inner))
+            path += &ident.to_string();
+            path
         }
         Type::CxxVector(ptr) => format!("::std::vector<{}>", to_typename(namespace, &ptr.inner)),
-        _ => unimplemented!(),
+        _ => unreachable!(),
     }
 }