[Bug #19426] Fix endless Range#step with #succ method

Merged: https://github.com/ruby/ruby/pull/7277

range.c

@@ -532,7 +532,11 @@ range_step(int argc, VALUE *argv, VALUE range)
                 rb_raise(rb_eTypeError, "can't iterate from %s",
                          rb_obj_classname(b));
             }
-            range_each_func(range, step_i, (VALUE)iter);
+            if (!NIL_P(e))
+                range_each_func(range, step_i, (VALUE)iter);
+            else
+                for (;; b = rb_funcallv(b, id_succ, 0, 0))
+                    step_i(b, (VALUE)iter);
         }
     }
     return range;

test/ruby/test_range.rb

@@ -392,6 +392,26 @@ class TestRange < Test::Unit::TestCase
     assert_equal(4, (1.0...5.6).step(1.5).to_a.size)
   end
 
+  def test_step_with_succ
+    c = Struct.new(:i) do
+      def succ; self.class.new(i+1); end
+      def <=>(other) i <=> other.i;end
+    end.new(0)
+
+    result = []
+    (c..c.succ).step(2) do |d|
+      result << d.i
+    end
+    assert_equal([0], result)
+
+    result = []
+    (c..).step(2) do |d|
+      result << d.i
+      break if d.i >= 4
+    end
+    assert_equal([0, 2, 4], result)
+  end
+
   def test_each
     a = []
     (0..10).each {|x| a << x }
@@ -456,6 +476,26 @@ class TestRange < Test::Unit::TestCase
     assert_equal(["a", "b", "c"], a)
   end
 
+  def test_each_with_succ
+    c = Struct.new(:i) do
+      def succ; self.class.new(i+1); end
+      def <=>(other) i <=> other.i;end
+    end.new(0)
+
+    result = []
+    (c..c.succ).each do |d|
+      result << d.i
+    end
+    assert_equal([0, 1], result)
+
+    result = []
+    (c..).each do |d|
+      result << d.i
+      break if d.i >= 4
+    end
+    assert_equal([0, 1, 2, 3, 4], result)
+  end
+
   def test_begin_end
     assert_equal(0, (0..1).begin)
     assert_equal(1, (0..1).end)