Function impl_method_c_wrapper_ident 

pub(crate) fn impl_method_c_wrapper_ident(
    type_ident: &Ident,
    label: Option<&str>,
    method_ident: &Ident,
) -> Ident

C_<crate>_<Type>__<method>, or C_<crate>_<Type>_<label>_<method> when the impl block carries a label — impl-method C wrapper identifier.