From: Nobuyoshi Nakada <nobu@...>
Date: 2011-01-10T14:54:53+09:00
Subject: [ruby-core:34290] Re: [Ruby 1.9-Feature#4254][Open] Allow method transplanting

Hi,

At Mon, 10 Jan 2011 10:14:34 +0900,
Yukihiro Matsumoto wrote in [ruby-core:34283]:
> No, I am thinking of methods defined for modules, that have no
> assumption of the type of receivers.  Ruby methods in C does not check
> the type of the receiver, so that if you move a method from String
> class to, say, Array, the interpreter will crash when you call the
> transplanted method.

Just between modules?

* proc.c (rb_mod_define_method): allow method transplanting
  between modules.  [ruby-core:34267]

diff --git i/proc.c w/proc.c
index 9ecf626..6affba6 100644
--- i/proc.c
+++ w/proc.c
@@ -1303,7 +1303,8 @@ rb_mod_define_method(int argc, VALUE *argv, VALUE mod)
     if (rb_obj_is_method(body)) {
 	struct METHOD *method = (struct METHOD *)DATA_PTR(body);
 	VALUE rclass = method->rclass;
-	if (rclass != mod && !RTEST(rb_class_inherited_p(mod, rclass))) {
+	if (rclass != mod && !(RB_TYPE_P(rclass, T_MODULE) && RB_TYPE_P(mod, T_MODULE)) &&
+	    !RTEST(rb_class_inherited_p(mod, rclass))) {
 	    if (FL_TEST(rclass, FL_SINGLETON)) {
 		rb_raise(rb_eTypeError,
 			 "can't bind singleton method to a different class");
diff --git i/test/ruby/test_method.rb w/test/ruby/test_method.rb
index fa5f998..0cbc785 100644
--- i/test/ruby/test_method.rb
+++ w/test/ruby/test_method.rb
@@ -36,7 +36,7 @@ class TestMethod < Test::Unit::TestCase
   module M
     def func; end
     module_function :func
-    def meth; end
+    def meth; :meth end
   end
 
   def mv1() end
@@ -205,6 +205,11 @@ class TestMethod < Test::Unit::TestCase
     assert_raise(TypeError) do
       Class.new.class_eval {define_method(:meth, M.instance_method(:meth))}
     end
+
+    feature4254 = '[ruby-core:34267]'
+    m = Module.new
+    m.module_eval {define_method(:meth, M.instance_method(:meth))}
+    assert_equal(:meth, Object.new.extend(m).meth, feature4254)
   end
 
   def test_clone


-- 
Nobu Nakada