Functions with Block parameters in Objective-C templates don't erase types.

Some of the annoying things in the Foundation Framework have blocks in generics as seen here.

Another odd thing about this is that it may be dependent on clang itself as I've had different results from macOS 10.14 to 10.15.

Input C/C++ Header

// bindgen-flags: --generate-block --objc-extern-crate -- -x objective-c -fblocks
// bindgen-osx-only

@interface FooWithBlock<__covariant ObjectType>
- (void)enumerateObjectsUsingBlock:(void (^)(ObjectType obj, int idx))block;
@end

Bindgen Invocation

$ bindgen input.h --generate-block --objc-extern-crate --block-extern-crate -- -x objective-c -fblocks

Actual Results

/* automatically generated by rust-bindgen */

#[macro_use]
extern crate objc;
#[allow(non_camel_case_types)]
pub type id = *mut objc::runtime::Object;
use block;
pub trait FooWithBlock<ObjectType> {
    unsafe fn enumerateObjectsUsingBlock_(self, block: _bindgen_ty_id_5);
}
impl<ObjectType: 'static> FooWithBlock<ObjectType> for id {
    unsafe fn enumerateObjectsUsingBlock_(self, block: _bindgen_ty_id_5) {
        msg_send!(self, enumerateObjectsUsingBlock: block)
    }
}
pub type _bindgen_ty_id_5 =
    *const ::block::Block<(*mut ObjectType, ::std::os::raw::c_int), ()>;

The issue here being _bindgen_ty_id_5 having ObjectType outside of it.

Expected Results

It's unclear what _bindgen_ty_id_5_ really should be.

Start with the supplied input.h and bindgen invocation, then reproduce the generated _bindgen_ty_id_5 that references ObjectType outside its generic scope. Compare the output across the noted macOS and Clang versions; done means the expected block type is defined and the input has a regression test covering the corrected behavior.