Function trait_member_c_wrapper_string 

pub(crate) fn trait_member_c_wrapper_string(
    type_ident: &Ident,
    trait_name: &Ident,
    member_ident: &Ident,
) -> String

C_<crate>_<Type>__<Trait>__<member> as a String — shared by TraitMethod and TraitConst, and by both the ident and string forms each needs, so the format string can’t drift across the four call sites that used to duplicate it.