Set Bullet Behavior "Strict Subproofs".
Open Scope string_scope.
Section Jspec'_properties.
Variables
(CS : compspecs)
(ext_link : string -> ident)
(ext_link_inj : forall s1 s2, ext_link s1 = ext_link s2 -> s1 = s2).
Definition Jspec' := (@OK_spec (Concurrent_Espec unit CS ext_link)).

Lemma is_EF_external ef : ext_spec_type Jspec' ef -> exists name sg, ef = EF_external name sg.
Open Scope string_scope.