Fix bug: Enum.slice selecting extra element (#12043)

Author: sabiwara

lib/elixir/lib/enum.ex

@@ -4436,7 +4436,10 @@ defmodule Enum do
           end
 
         entry, {start, amount, to_drop, list} ->
-          {:halt, {start, amount, to_drop, [entry | list]}}
+          case to_drop do
+            1 -> {:halt, {start, amount, to_drop, [entry | list]}}
+            _ -> {:halt, {start, amount, to_drop, list}}
+          end
       end)
 
     :lists.reverse(slice)

lib/elixir/test/elixir/enum_test.exs

@@ -1077,6 +1077,7 @@ defmodule EnumTest do
     assert [1, 2, 3] |> Stream.cycle() |> Enum.slice(0..1) == [1, 2]
     assert [1, 2, 3] |> Stream.cycle() |> Enum.slice(0..4) == [1, 2, 3, 1, 2]
     assert [1, 2, 3] |> Stream.cycle() |> Enum.slice(0..4//2) == [1, 3, 2]
+    assert [1, 2, 3] |> Stream.cycle() |> Enum.slice(0..5//2) == [1, 3, 2]
   end
 
   test "slice on pruned infinite streams" do