Function binding_to_core_match_arm 

pub fn binding_to_core_match_arm(
    binding_prefix: &str,
    variant_name: &str,
    fields: &[FieldDef],
) -> String

Generate a match arm for binding -> core direction. Binding enums are always unit-variant-only. Core enums may have data variants. For data variants: BindingEnum::Variant => CoreEnum::Variant(Default::default(), ...)