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 exprD_ex_typs : forall tus tvs t (e1 e2 : expr typ func) v,
exprD' tus tvs t (App e1 e2) = Some v ->
exists t2, typeof_expr tus tvs e1 = Some (tyArr t2 t) /\
typeof_expr tus tvs e2 = Some (t2).