Type Kernel#<=> as returning Integer?

core/kernel.rbs

@@ -2306,7 +2306,7 @@ module Kernel : BasicObject
   # When you define #<=>, you can include Comparable to gain the methods #<=, #<,
   # #==, #>=, #> and #between?.
   #
-  def <=>: (untyped other) -> 0?
+  def <=>: (untyped other) -> Integer?
 
   # <!--
   #   rdoc-file=object.c

test/stdlib/Kernel_test.rb

@@ -581,7 +581,7 @@ def test_op_cmp
     obj = JustKernel.new.__with_object_methods(:==) # needed because <=> has an implicit dependency on it.
 
     with_untyped.and obj do |other|
-      assert_send_type  '(untyped) -> 0?',
+      assert_send_type  '(untyped) -> Integer?',
                         obj, :<=>, other
     end
   end