Fixed bug: Using 'open-uri' with 'tempfile' causes an exception.

lib/open-uri.rb

@@ -27,7 +27,7 @@ class << self
   # We can accept URIs and strings that begin with http://, https:// and
   # ftp://. In these cases, the opened file object is extended by OpenURI::Meta.
   def open(name, *rest, &block) # :doc:
-    if name.respond_to?(:open)
+    if name.respond_to?(:open) && !name.method(:open).parameters.empty?
       name.open(*rest, &block)
     elsif name.respond_to?(:to_str) &&
           %r{\A[A-Za-z][A-Za-z0-9+\-\.]*://} =~ name &&

test/open-uri/test_open-uri.rb

@@ -3,6 +3,7 @@
 require 'open-uri'
 require 'webrick'
 require 'webrick/httpproxy'
+require 'tempfile'
 begin
   require 'zlib'
 rescue LoadError
@@ -115,6 +116,13 @@ def test_open_too_many_arg
     assert_raise(ArgumentError) { open("http://192.0.2.1/tma", "r", 0666, :extra) {} }
   end
 
+  def test_tempfile_rest_parameter
+    temp_file = Tempfile.new
+    assert_nothing_raised { open(temp_file, 'a') }
+  ensure
+    temp_file.close
+  end
+
   def test_read_timeout
     TCPServer.open("127.0.0.1", 0) {|serv|
       port = serv.addr[1]