more rigid type_name demands, based on educated guesses about the tools involved here;
(* Title: HOL/HOLCF/IOA/Storage/Action.thy
Author: Olaf Müller
*)
header {* The set of all actions of the system *}
theory Action
imports Main
begin
datatype action = New | Loc nat | Free nat
lemma [cong]: "!!x. x = y ==> case_action a b c x = case_action a b c y"
by simp
end