Section tbled.
Variable tbl : SymEnv.functions RType_typ.
Let RSym_sym := RSym_sym tbl.
Existing Instance RSym_sym.
Let RSym_sym_ok :  RSymOk RSym_sym := _.
Existing Instance RSym_sym_ok.
Let Expr_expr_fs := Expr_expr_fs tbl.
Existing Instance Expr_expr_fs.
Let Expr_ok_fs := Expr_ok_fs tbl.
Existing Instance Expr_ok_fs.
Existing Instance MA.

Lemma typeof_app : forall (e1 e2 : expr typ func) t tvs tus,
typeof_expr tus tvs (App e1 e2) = Some t ->
exists t2, typeof_expr tus tvs e1 = Some (tyArr t2 t) /\
typeof_expr tus tvs e2 = Some (t2).