Roundtrip test failed

AST 1:

Module (SrcLoc {srcFilename = "", srcLine = -1, srcColumn = -1}) (ModuleName "Main") [] Nothing (Just [EVar (UnQual (Ident "main"))]) [] [TypeSig (SrcLoc {srcFilename = "", srcLine = -1, srcColumn = -1}) [Ident "happyThen"] (TyForall Nothing [] (TyApp (TyCon (UnQual (Ident "P"))) (TyVar (Ident "a"))))]

AST 2:

Module (SrcLoc {srcFilename = "", srcLine = -1, srcColumn = -1}) (ModuleName "Main") [] Nothing (Just [EVar (UnQual (Ident "main"))]) [] [TypeSig (SrcLoc {srcFilename = "", srcLine = -1, srcColumn = -1}) [Ident "happyThen"] (TyApp (TyCon (UnQual (Ident "P"))) (TyVar (Ident "a")))]