Function rustc_builtin_macros::deriving::generic::cs_fold_enumnonmatch

pub fn cs_fold_enumnonmatch(
    enum_nonmatch_f: Box<dyn FnMut(&mut ExtCtxt<'_>, Span, (&[Ident], &[Ident]), &[P<Expr>]) -> P<Expr> + '_>, 
    cx: &mut ExtCtxt<'_>, 
    trait_span: Span, 
    substructure: &Substructure<'_>
) -> P<Expr>