diff --git a/typecheck.ml b/typecheck.ml
new file mode 100644
index 000000000..2d7565907
--- /dev/null
+++ b/typecheck.ml
@@ -0,0 +1,32 @@
+open AST
+open Region
+
+module SMap = Map.Make(String)
+
+(* open Sanity: *)
+let (|>) v f = f v
+let (@@) f v = f v
+let map f l = List.rev (List.rev_map f l)
+
+let type_decl_to_tenv td =
+  td
+  |> List.map (fun (_, name, _, type_expr) -> (name, type_expr))
+  |> List.to_seq |> SMap.of_seq
+
+let shadow name typ env =
+  SMap.update name (function None -> Some [typ] | Some tl -> Some (typ :: tl)) env
+
+let shadow_list name_typ_list env =
+  List.fold_left (fun  acc (name, typ) -> shadow name typ acc) env name_typ_list
+
+let tc ast =
+  (* te is the type environment, ve is the variable environment *)
+  let te = type_decl_to_tenv ast#types in
+  let ve =
+    SMap.empty
+    |> (match ast#parameter.value with (_,name,_,ty) -> shadow name ty)
+    |> shadow "storage"    (snd ast#storage.value)
+    |> shadow "operations" (snd ast#operations.value)
+    (* |> shadow_list @@ map (function FunDecl {value} -> value.var.value, ) lambdas *)
+  in
+  te, ve