2 files changed, 67 insertions, 3 deletions
diff --git a/range.c b/range.c
index 7ddb9908f6..e6c2897083 100644
--- a/range.c
+++ b/range.c
@@ -908,6 +908,10 @@ sym_each_i(VALUE v, VALUE arg)
     return each_i(rb_str_intern(v), arg);
 }
 
+#define CANT_ITERATE_FROM(x) \
+    rb_raise(rb_eTypeError, "can't iterate from %s", \
+             rb_obj_classname(x))
+
 /*
  *  call-seq:
  *    size -> non_negative_integer or Infinity or nil
@@ -944,13 +948,48 @@ range_size(VALUE range)
     }
 
     if (!discrete_object_p(b)) {
-        rb_raise(rb_eTypeError, "can't iterate from %s",
-                 rb_obj_classname(b));
+        CANT_ITERATE_FROM(b);
     }
 
     return Qnil;
 }
 
+static VALUE
+range_reverse_size(VALUE range)
+{
+    VALUE b = RANGE_BEG(range), e = RANGE_END(range);
+
+    if (NIL_P(e)) {
+        CANT_ITERATE_FROM(e);
+    }
+
+    if (RB_INTEGER_TYPE_P(b)) {
+        if (rb_obj_is_kind_of(e, rb_cNumeric)) {
+            return ruby_num_interval_step_size(b, e, INT2FIX(1), EXCL(range));
+        }
+        else {
+            CANT_ITERATE_FROM(e);
+        }
+    }
+
+    if (NIL_P(b)) {
+        if (RB_INTEGER_TYPE_P(e)) {
+            return DBL2NUM(HUGE_VAL);
+        }
+        else {
+            CANT_ITERATE_FROM(e);
+        }
+    }
+
+    if (!discrete_object_p(b)) {
+        CANT_ITERATE_FROM(e);
+    }
+
+    return Qnil;
+}
+
+#undef CANT_ITERATE_FROM
+
 /*
  *  call-seq:
  *    to_a -> array
@@ -979,6 +1018,12 @@ range_enum_size(VALUE range, VALUE args, VALUE eobj)
     return range_size(range);
 }
 
+static VALUE
+range_enum_reverse_size(VALUE range, VALUE args, VALUE eobj)
+{
+    return range_reverse_size(range);
+}
+
 RBIMPL_ATTR_NORETURN()
 static void
 range_each_bignum_endless(VALUE beg)
@@ -1225,7 +1270,7 @@ range_reverse_each_negative_bignum_section(VALUE beg, VALUE end)
 static VALUE
 range_reverse_each(VALUE range)
 {
-    RETURN_SIZED_ENUMERATOR(range, 0, 0, range_enum_size);
+    RETURN_SIZED_ENUMERATOR(range, 0, 0, range_enum_reverse_size);
 
     VALUE beg = RANGE_BEG(range);
     VALUE end = RANGE_END(range);
diff --git a/test/ruby/test_range.rb b/test/ruby/test_range.rb
index e0c1d20bd2..480f213029 100644
--- a/test/ruby/test_range.rb
+++ b/test/ruby/test_range.rb
@@ -823,6 +823,25 @@ class TestRange < Test::Unit::TestCase
     assert_equal [5, 4, 3, 2, 1], a
   end
 
+  def test_reverse_each_size
+    assert_equal(3, (1..3).reverse_each.size)
+    assert_equal(3, (1..3.3).reverse_each.size)
+    assert_raise(TypeError) { (1..nil).reverse_each.size }
+    assert_raise(TypeError) { (1.1..3).reverse_each.size }
+    assert_raise(TypeError) { (1.1..3.3).reverse_each.size }
+    assert_raise(TypeError) { (1.1..nil).reverse_each.size }
+    assert_equal(Float::INFINITY, (..3).reverse_each.size)
+    assert_raise(TypeError) { (nil..3.3).reverse_each.size }
+    assert_raise(TypeError) { (nil..nil).reverse_each.size }
+
+    assert_equal(2, (1...3).reverse_each.size)
+    assert_equal(3, (1...3.3).reverse_each.size)
+
+    assert_equal(nil, ('a'..'z').reverse_each.size)
+    assert_raise(TypeError) { ('a'..).reverse_each.size }
+    assert_raise(TypeError) { (..'z').reverse_each.size }
+  end
+
   def test_begin_end
     assert_equal(0, (0..1).begin)
     assert_equal(1, (0..1).end)