checkpoint

lib/debug.ex

@@ -606,9 +606,9 @@ defmodule Tdd.Debug do
 
   # --- TDD Graph Printing (Kept as it was, assuming it's for a different purpose) ---
   @doc "Prints a formatted representation of a TDD graph structure."
-  def print_tdd_graph(id, store_module \\ Tdd.Store) do
-    IO.puts("--- TDD Graph (ID: #{id}) ---")
-    do_print_tdd_node(id, 0, MapSet.new(), store_module)
+  def print_tdd_graph(id, label \\ "") do
+    IO.puts("---#{label} TDD Graph (ID: #{id}) ---")
+    do_print_tdd_node(id, 0, MapSet.new(), Tdd.Store)
     IO.puts("------------------------")
   end
 

lib/til.ex

@@ -1357,6 +1357,7 @@ defmodule Tdd.Algo do
         Store.put_op_cache(cache_key, result_id)
         result_id
     end
+    |> simplify()
   end
 
   # This function is correct and does not need to be changed.
@@ -2120,9 +2121,13 @@ defmodule Tdd.Compiler do
     Store.init()
 
     id1 = spec_to_id(spec1)
+    Debug.print_tdd_graph(id1, "IS_SUBTYPE id1")
     id2 = spec_to_id(spec2)
+    Debug.print_tdd_graph(id2, "IS_SUBTYPE id2")
     neg_id2 = Algo.negate(id2)
+    Debug.print_tdd_graph(neg_id2, "IS_SUBTYPE neg_id2")
     intersect_id = Algo.apply(:intersect, &op_intersect_terminals/2, id1, neg_id2)
+    Debug.print_tdd_graph(intersect_id, "IS_SUBTYPE intersect")
 
     # The crash was because `intersect_id` was not an integer, which should not
     # happen if `apply` works correctly on valid IDs. By fixing the state

test/til_test.exs

@@ -380,22 +380,20 @@ defmodule TddSystemTest do
   # These tests target the most complex features: recursive and polymorphic types.
   # ---
   describe "Tdd.Compiler: Advanced Features (μ, Λ, Apply)" do
-    @doc """
-    It checks for covariance in generic types: a list of integers is a subtype of a list of anything,
-    but the reverse is not true. This requires the system to correctly handle coinductive reasoning
-    on the recursive TDD nodes.
-    """
-    test "the previously crashing recursive subtype test now passes" do
+    test "list subtyping: list(int) <: list(any)" do
       int_list = {:list_of, :integer}
       any_list = {:list_of, :any}
       assert_subtype(:integer, :any)
-      # The key test that was failing due to the bug
       assert_subtype(int_list, any_list)
-      refute_subtype(any_list, int_list)
-
-      # Also test instances against the recursive type
       assert_subtype({:cons, {:literal, 1}, {:literal, []}}, int_list)
+    end
+
+    test "list subtyping: list(any) <! list(integer)" do
+      int_list = {:list_of, :integer}
+      any_list = {:list_of, :any}
+      assert_subtype(:integer, :any)
       refute_subtype({:cons, {:literal, :a}, {:literal, []}}, int_list)
+      refute_subtype(any_list, int_list)
     end
 
     @doc "Tests that manually-defined recursive types (like a binary tree) can be compiled and checked correctly."