proposition: Lemma duplicate_type_length ls : List.length (duplicate_type ls) = List.length ls.
proof: Proof. apply List.map_length. Qed.
imports: Coq.Lists.List Coq.Arith.EqNat Coq.Logic.Eqdep_dec Fiat.Parsers.Reflective.Syntax Fiat.Parsers.Reflective.SyntaxEquality Fiat.Parsers.Reflective.SyntaxEquivalence Fiat.Common.PointedProp Fiat.Common.OptionFacts Fiat.Common.Prod Fiat.Common.Sigma Fiat.Common