Attempt to fix Hash#rehash spec

spec/ruby/core/hash/rehash_spec.rb

@@ -3,23 +3,26 @@ require_relative 'fixtures/classes'
 
 describe "Hash#rehash" do
   it "reorganizes the hash by recomputing all key hash codes" do
-    k1 = [1]
-    k2 = [2]
+    k1 = Object.new
+    k2 = Object.new
+    def k1.hash; 0; end
+    def k2.hash; 1; end
+
     h = {}
-    h[k1] = 0
-    h[k2] = 1
+    h[k1] = :v1
+    h[k2] = :v2
 
-    k1 << 2
+    def k1.hash; 1; end
 
-    # if k1 is modified to k1', k1.hash and k1'.hash can be same.
-    # So this test has an issue. For the present, this line is commented out.
-    # h.key?(k1).should == false
+    # The key should no longer be found as the #hash changed.
+    # Hash values 0 and 1 should not conflict, even with 1-bit stored hash.
+    h.key?(k1).should == false
 
     h.keys.include?(k1).should == true
 
     h.rehash.should equal(h)
     h.key?(k1).should == true
-    h[k1].should == 0
+    h[k1].should == :v1
 
     k1 = mock('k1')
     k2 = mock('k2')