Ltac destruct_match H :=
match type of H with
| context [ match ?x with _ => _  end] => destruct x eqn:?
end.
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_typeof_Some : forall tus tvs t (e : expr typ func) val,
exprD' tus tvs t e = Some val -> typeof_expr tus tvs e = Some t.