Make leaf intersection recursive

Author: josevalim

lib/elixir/lib/module/types/descr.ex

@@ -5014,15 +5014,23 @@ defmodule Module.Types.Descr do
   #
   # Which is equivalent to:
   #
-  #     (a1 and B2) or (B2 and (U2 or not a1 and D2))
+  #     (a1 and B2) or (B2 and U2) or (B2 and not a1 and D2)
   defp bdd_intersection({leaf, :bdd_top, u, d}, bdd, leaf_intersection) do
     bdd_leaf_intersection(leaf, bdd, leaf_intersection)
-    |> bdd_union(bdd_intersection(bdd, {leaf, :bdd_bot, u, d}))
+    |> bdd_union(bdd_intersection(u, bdd, leaf_intersection))
+    |> case do
+      result when d == :bdd_bot -> result
+      result -> bdd_union(result, bdd_intersection(bdd, {leaf, :bdd_bot, :bdd_bot, d}))
+    end
   end
 
   defp bdd_intersection(bdd, {leaf, :bdd_top, u, d}, leaf_intersection) do
     bdd_leaf_intersection(leaf, bdd, leaf_intersection)
-    |> bdd_union(bdd_intersection(bdd, {leaf, :bdd_bot, u, d}))
+    |> bdd_union(bdd_intersection(u, bdd, leaf_intersection))
+    |> case do
+      result when d == :bdd_bot -> result
+      result -> bdd_union(result, bdd_intersection(bdd, {leaf, :bdd_bot, :bdd_bot, d}))
+    end
   end
 
   defp bdd_intersection(bdd1, bdd2, _leaf_intersection) do