Parse records and keyed collection queries

test/fixture/revenue.delta

@@ -0,0 +1,11 @@
+type order = {
+  customer : string;
+  total : int;
+}
+
+input orders : collection order
+
+let tax n = n * 20 / 100
+
+query revenue =
+  orders |> map (fun o -> tax o.total) |> sum