If there really serious about this, they'll realize they need to add erased but not specialized types to rust, and existential types.

If you can replace

    void qsort(void base[.size * .nmemb], size_t nmemb, size_t size,
               int (*compar)(const void [.size], const void [.size]))

with

    extern "C" fn qsort<erase T>(base: *const T, nmemb: usize, compar: fn(*const T, *const T) -> std::ffi::c_int)

such that `qsort` is still single a regular C function, not something that corresponds to many separate C functions, many good things are possible.

In particular for C++, being able to do

    struct MyVTable<erase T> {
        virt_method_0: fn(*const T) -> bool,
        virt_method_2: fn(*const T, usize) -> (usize, usize),
    };

    struct MyType<erase R> {
        vtable: *const MyVTable<MyType<R>>,
        rest_of_fields: R, 
    };

Opens a lot of doors. People while whine because it is exposing the C++ ABI in the Rust API, but that's fine. That's what `private` is there to fix.