Function build_fn_ptr_as_ptr_shim 

fn build_fn_ptr_as_ptr_shim<'tcx>(
    tcx: TyCtxt<'tcx>,
    def_id: DefId,
    self_ty: Ty<'tcx>,
) -> Body<'tcx>

impl FnPtr for fn(u32) {
    fn addr(self) -> NonNull<Code> {
        unsafe { transmute(self as *const Code)}
    }
}