string.c: rindex(//) should set $~.

This seems a bug introduced by r520 (1.4.0).  [ruby-core:79110] [Bug #13135]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@57374 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

string.c

@@ -3516,10 +3516,8 @@ rb_str_rindex_m(int argc, VALUE *argv, VALUE str)
 	pos = str_offset(RSTRING_PTR(str), RSTRING_END(str), pos,
 			 enc, single_byte_optimizable(str));
 
-	if (!RREGEXP_PTR(sub) || RREGEXP_SRC_LEN(sub)) {
+	pos = rb_reg_search(sub, str, pos, 1);
-	    pos = rb_reg_search(sub, str, pos, 1);
+	pos = rb_str_sublen(str, pos);
-	    pos = rb_str_sublen(str, pos);
-	}
 	if (pos >= 0) return LONG2NUM(pos);
 	break;
 

test/ruby/test_string.rb

@@ -1227,6 +1227,9 @@ CODE
 
     assert_nil("foo".rindex(//, -100))
     assert_nil($~)
+
+    assert_equal(3, "foo".rindex(//))
+    assert_equal([3, 3], $~.offset(0))
   end
 
   def test_rjust