Fixed Regexp backreference corruption

Regular expression parsing was switched to use single-quote escaping
rules.  Using double quote rules, extra backslashes and white spaces was
added.

See also Ruby Bug #6488 and #6523

Author: drbrain

lib/rdoc/ruby_lex.rb

@@ -1189,14 +1189,16 @@ def identify_string(ltype, quoted = ltype, type = nil)
           else
             ungetc
           end
-        elsif ch == '\\' and @ltype == "'" #'
-          case ch = getc
-          when "\\", "\n", "'"
+        elsif ch == '\\'
+          if %w[' /].include? @ltype then
+            case ch = getc
+            when "\\", "\n", "'"
+            else
+              ungetc
+            end
           else
-            ungetc
+            str << read_escape
           end
-        elsif ch == '\\' #'
-          str << read_escape
         end
 
         if close then

test/test_rdoc_ruby_lex.rb

@@ -127,6 +127,17 @@ def test_class_tokenize_regexp
     assert_equal expected, tokens
   end
 
+  def test_class_tokenize_regexp_backref
+    tokens = RDoc::RubyLex.tokenize "/[csh](..) [csh]\\1 in/", nil
+
+    expected = [
+      @TK::TkREGEXP.new( 0, 1,  0, "/[csh](..) [csh]\\1 in/"),
+      @TK::TkNL    .new(22, 1, 22, "\n"),
+    ]
+
+    assert_equal expected, tokens
+  end
+
   def test_class_tokenize_string
     tokens = RDoc::RubyLex.tokenize "'hi'", nil