Function call_slot_ident 

pub(crate) fn call_slot_ident() -> Ident

The C wrapper’s call slot, declared by CWrapperContext with quote!. A reference inside a quote_spanned! template would take the user type’s span instead. That only resolves while the macro’s call site is the user’s, not when the wrapper is generated inside a macro_rules! expansion, as a trait impl’s is (#1489). So references interpolate this.