Section DomLemmas.
Variables (K : ordType) (V : Type) (U : union_map_class K V).
Implicit Types (k : K) (v : V) (f g : U).
Variant dom_find_spec k f : bool -> Type :=
| dom_find_none' : find k f = None -> dom_find_spec k f false
| dom_find_some' v : find k f = Some v ->
f = upd k v (free k f) -> dom_find_spec k f true.

Lemma umfilt0 q : um_filter q Unit = Unit :> U.