Allow any type on the RHS of or/2 (#9706)

Closes #9704.

Author: ericmj

lib/elixir/lib/module/types.ex

@@ -57,7 +57,7 @@ defmodule Module.Types do
   def of_head(params, guards, stack, context) do
     with {:ok, types, context} <-
            map_reduce_ok(params, context, &Pattern.of_pattern(&1, stack, &2)),
-         # TODO: Check that of_guard/3 returns a boolean
+         # TODO: Check that of_guard/3 returns boolean() | :fail
          {:ok, _, context} <- Pattern.of_guard(guards_to_or(guards), stack, context),
          do: {:ok, lift_types(types, context), context}
   end

lib/elixir/lib/module/types/pattern.ex

@@ -333,10 +333,9 @@ defmodule Module.Types.Pattern do
     fresh_context = fresh_context(context)
 
     with {:ok, left_type, left_context} <- of_guard(left, stack, fresh_context),
-         {:ok, right_type, right_context} <- of_guard(right, stack, fresh_context),
+         {:ok, _right_type, right_context} <- of_guard(right, stack, fresh_context),
          {:ok, context} <- merge_context_or(context, stack, left_context, right_context),
          {:ok, _, context} <- unify(left_type, :boolean, stack, context),
-         {:ok, _, context} <- unify(right_type, :boolean, stack, context),
          do: {:ok, :boolean, context}
   end
 

lib/elixir/test/elixir/module/types/pattern_test.exs

@@ -225,6 +225,11 @@ defmodule Module.Types.PatternTest do
     assert {:ok, :dynamic, context} = quoted_guard([x], elem(x, 0))
     assert Types.lift_type({:var, 0}, context) == :tuple
 
+    assert {:ok, {:atom, true}, context} = quoted_guard([], true)
+    assert {:ok, {:atom, false}, context} = quoted_guard([], false)
+    assert {:ok, {:atom, :fail}, context} = quoted_guard([], :fail)
+    assert {:ok, :boolean, context} = quoted_guard([], is_atom(true or :fail))
+
     assert {:error, {_, {:unable_unify, :tuple, :boolean, _, _}, _}} =
              quoted_guard([x], is_tuple(x) and is_boolean(x))
   end