Function syntex_syntax::ext::deriving::generic::cs_same_method_fold

pub fn cs_same_method_fold<F>(use_foldl: bool, f: F, base: P<Expr>, enum_nonmatch_f: EnumNonMatchCollapsedFunc, cx: &mut ExtCtxt, trait_span: Span, substructure: &Substructure) -> P<Expr> where F: FnMut(&mut ExtCtxt, Span, P<Expr>, P<Expr>) -> P<Expr>

Fold together the results of calling the derived method on all the fields. use_foldl controls whether this is done left-to-right (true) or right-to-left (false).