objc: Handle template params

The objetive-c template type params were handled as Typedefs so every
interface generated its own, clashing in the namespace. This now maps them to id.

src/ir/ty.rs

@@ -836,6 +836,24 @@ impl Type {
             _ => {}
         }
 
+        // Objective C template type parameter
+        // FIXME: This is probably wrong, we are attempting to find the
+        //        objc template params, which seem to manifest as a typedef.
+        //        We are rewriting them as id to suppress multiple conflicting
+        //        typedefs at root level
+        if ty_kind == CXType_Typedef {
+            let is_template_type_param = ty.declaration().kind() == CXCursor_TemplateTypeParameter;
+            let is_canonical_objcpointer = canonical_ty.kind() == CXType_ObjCObjectPointer;
+
+            // We have found a template type for objc interface
+            if is_canonical_objcpointer && is_template_type_param {
+                // Objective-C generics are just ids with fancy name.
+                // To keep it simple, just name them ids
+                name = "id".to_owned();
+            }
+
+        }
+
         if location.kind() == CXCursor_ClassTemplatePartialSpecialization {
             // Sorry! (Not sorry)
             warn!("Found a partial template specialization; bindgen does not \

tests/expectations/tests/objc_template.rs

@@ -0,0 +1,18 @@
+/* automatically generated by rust-bindgen */
+
+
+#![allow(non_snake_case)]
+
+#![cfg(target_os="macos")]
+
+#[macro_use]
+extern crate objc;
+#[allow(non_camel_case_types)]
+pub type id = *mut objc::runtime::Object;
+pub trait Foo {
+    unsafe fn get(self)
+    -> id;
+}
+impl Foo for id {
+    unsafe fn get(self) -> id { msg_send!(self , get) }
+}

tests/headers/objc_template.h

@@ -0,0 +1,6 @@
+// bindgen-flags: --objc-extern-crate -- -x objective-c
+// bindgen-osx-only
+
+@interface Foo<__covariant ObjectType>
+- (ObjectType)get;
+@end