1 files changed, 15 insertions, 0 deletions

diff --git a/lib/account/type.ml b/lib/account/type.ml
new file mode 100644
index 0000000..ad7a46e
--- /dev/null
+++ b/lib/account/type.ml
@@ -0,0 +1,15 @@
+type t = Type_hierarchy.path [@@deriving equal]
+
+let rec base (t : t) : t =
+  match Type_hierarchy.super t with
+  | None -> (* [t] is a base type *) t
+  | Some t' -> base t'
+
+(** [a] is a (strict) supertype of [b] *)
+let is_super t ~super ~strict =
+  Type_hierarchy.is_prefix super ~prefix:t
+  &&
+  (* strict → t ≠ super *)
+  ((not strict) || not ([%equal: t] t super))
+
+let polarity = Type_hierarchy.polarity