[RCR] Module#method_aliased and Module#singleton_method_aliased

Hi all,

Since David mentioned that RCRchive is being reworked, I thought I'd propose
this here.

Abstract:
   Add the Module#method_aliased and Method#singleton_method_aliased hooks.

Problem:
   There is currently no hook to determine whether or not a method has been
   aliased.  In some circumstances a user may want to ensure that the
aliased
   methods for their class are automatically remapped if the original method
is
   redefined.

Proposal:
   The ability to automatically remap aliased methods can be accomplished if
   we add the Module#method_aliased and Method#singleton_method_aliased
methods.

   Consider the following example:

   class Foo
      def bar; "bar"; end
      alias baz bar
   end

   puts Foo.new.bar => "bar"
   puts Foo.new.baz => "bar"

   Then later on, you decide to re-open the Foo#bar method:

   class Foo
      def bar
         "test"
      end
   end

   puts Foo.new.bar => "test"
   puts Foo.new.baz => "bar"  # Alias doesn't get remapped

   With our hypothetical Module#method_aliased method, a user could
   automatically remap any aliases by combining it with Module#method_added:

   class Foo
      @@aliases = Hash.new{ |hash, key| hash[key] = [] }

      def self.method_aliased(new_id, old_id)
         new_name = new_id.id2name
         old_name = old_id.id2name

         unless @@aliases[old_name].include?(new_name)
            @@aliases[old_name] << new_name
         end
      end

      def self.method_added(id)
         return unless @@aliases.keys.include?(id.id2name)
         @@aliases.each{ |method, aliases|
            aliases.each{ |a|
               alias_method a.to_sym, id
            }
         }
      end

      def bar
         "bar"
      end

      alias baz bar
   end

   puts Foo.new.bar => "bar"
   puts Foo.new.baz => "bar"

   class Foo
      def bar
         "test"
      end
   end

   puts Foo.new.bar => "test"
   puts Foo.new.baz => "test"

Analysis:
   No incompatibilities.  Requires minimal code changes to object.c and
   eval.c.

Implementation:
--- object.orig 2006-10-28 10:19:19.000000000 -0600
+++ object.c    2006-10-28 13:16:08.000000000 -0600
@@ -493,7 +493,6 @@
     return Qfalse;
 }

-
 /*
  * Document-method: singleton_method_added
  *
@@ -2570,7 +2569,7 @@
     rb_define_private_method(rb_cModule, "method_added", rb_obj_dummy, 1);
     rb_define_private_method(rb_cModule, "method_removed", rb_obj_dummy,
1);
     rb_define_private_method(rb_cModule, "method_undefined", rb_obj_dummy,
1);
-
+    rb_define_private_method(rb_cModule, "method_aliased", rb_obj_dummy,
2);

     rb_define_method(rb_mKernel, "nil?", rb_false, 0);
     rb_define_method(rb_mKernel, "==", rb_obj_equal, 1);
@@ -2618,6 +2617,7 @@
     rb_define_private_method(rb_mKernel, "singleton_method_added",
rb_obj_dummy, 1);
     rb_define_private_method(rb_mKernel, "singleton_method_removed",
rb_obj_dummy, 1);
     rb_define_private_method(rb_mKernel, "singleton_method_undefined",
rb_obj_dummy, 1);
+    rb_define_private_method(rb_mKernel, "singleton_method_aliased",
rb_obj_dummy, 2);

     rb_define_global_function("sprintf", rb_f_sprintf, -1); /* in sprintf.c*/
     rb_define_global_function("format", rb_f_sprintf, -1);  /* in sprintf.c
*/
@@ -2742,4 +2742,5 @@
     id_eql = rb_intern("eql?");
     id_inspect = rb_intern("inspect");
     id_init_copy = rb_intern("initialize_copy");
+
 }

--- eval.orig   2006-10-28 10:19:08.000000000 -0600
+++ eval.c      2006-10-28 13:17:42.000000000 -0600
@@ -408,6 +408,7 @@
 static ID init, eqq, each, aref, aset, match, missing;
 static ID added, singleton_added;
 static ID __id__, __send__, respond_to;
+static ID alias_added, singleton_alias_added;

 #define NOEX_TAINTED 8
 #define NOEX_SAFE(n) ((n) >> 4)
@@ -2163,9 +2164,11 @@
                                    NOEX_WITH_SAFE(orig->nd_noex)));
     if (singleton) {
        rb_funcall(singleton, singleton_added, 1, ID2SYM(name));
+   rb_funcall(singleton, singleton_alias_added, 2, ID2SYM(name),
ID2SYM(def));
     }
     else {
        rb_funcall(klass, added, 1, ID2SYM(name));
+   rb_funcall(klass, alias_added, 2, ID2SYM(name), ID2SYM(def));
     }
 }

@@ -7884,7 +7887,9 @@
     match = rb_intern("=~");
     missing = rb_intern("method_missing");
     added = rb_intern("method_added");
+    alias_added = rb_intern("method_aliased");
     singleton_added = rb_intern("singleton_method_added");
+    singleton_alias_added = rb_intern("singleton_method_aliased");
     removed = rb_intern("method_removed");
     singleton_removed = rb_intern("singleton_method_removed");
     undefined = rb_intern("method_undefined");