Do not raise when Stream.cycle is explicitly halted, closes #14307

Author: josevalim

lib/elixir/lib/stream.ex

@@ -1447,7 +1447,7 @@ defmodule Stream do
   defp check_cycle_first_element(reduce) do
     fn acc ->
       case reduce.(acc) do
-        {state, []} when state in [:done, :halted] ->
+        {state, []} when state in [:done, :halted] and elem(acc, 0) != :halt ->
           raise ArgumentError, "cannot cycle over an empty enumerable"
 
         other ->

lib/elixir/test/elixir/enum_test.exs

@@ -1521,6 +1521,18 @@ defmodule EnumTest do
     assert Enum.zip([], []) == []
   end
 
+  test "zip/2 with infinite streams" do
+    assert Enum.zip([], Stream.cycle([1, 2])) == []
+    assert Enum.zip([], Stream.cycle(1..2)) == []
+    assert Enum.zip(.., Stream.cycle([1, 2])) == []
+    assert Enum.zip(.., Stream.cycle(1..2)) == []
+
+    assert Enum.zip(Stream.cycle([1, 2]), ..) == []
+    assert Enum.zip(Stream.cycle(1..2), ..) == []
+    assert Enum.zip(Stream.cycle([1, 2]), ..) == []
+    assert Enum.zip(Stream.cycle(1..2), ..) == []
+  end
+
   test "zip/1" do
     assert Enum.zip([[:a, :b], [1, 2], ["foo", "bar"]]) == [{:a, 1, "foo"}, {:b, 2, "bar"}]