Separate meta-programming features to `mruby-metaprog` gem.

We assume meta-programming is less used in embedded environments.
We have moved following methods:

 * Kernel module
   global_variables, local_variables, singleton_class,
   instance_variables, instance_variables_defined?, instance_variable_get,
   instance_variable_set, methods, private_methods, public_methods,
   protected_methods, singleton_methods, define_singleton_methods

 * Module class
   class_variables, class_variables_defined?, class_variable_get,
   class_variable_set, remove_class_variable, included_modules,
   instance_methods, remove_method, method_removed, constants

 * Module class methods
   constants, nesting

Note:
Following meta-programming methods are kept in the core:

 * Module class
   alias_method, undef_method, ancestors, const_defined?, const_get,
   const_set, remove_const, method_defined?, define_method

 * Toplevel object
   define_method

`mruby-metaprog` gem is linked by default (specified in default.gembox).
When it is removed, it will save 40KB (stripped:8KB) on x86-64
environment last time I measured.

2 files changed, 10 insertions, 7 deletions

diff --git a/mrbgems/mruby-method/mrblib/kernel.rb b/mrbgems/mruby-method/mrblib/kernel.rb
index b2ebd45ea..2efc93f37 100644
--- a/mrbgems/mruby-method/mrblib/kernel.rb
+++ b/mrbgems/mruby-method/mrblib/kernel.rb
@@ -1,8 +1,9 @@
 module Kernel
   def singleton_method(name)
     m = method(name)
-    if m.owner != singleton_class
-      raise NameError, "undefined method `#{name}' for class `#{singleton_class}'"
+    sc = (class <<self; self; end)
+    if m.owner != sc
+      raise NameError, "undefined method `#{name}' for class `#{sc}'"
     end
     m
   end
diff --git a/mrbgems/mruby-method/test/method.rb b/mrbgems/mruby-method/test/method.rb
index b229a4560..eb5f48341 100644
--- a/mrbgems/mruby-method/test/method.rb
+++ b/mrbgems/mruby-method/test/method.rb
@@ -149,7 +149,7 @@ assert 'Method#source_location' do
   assert_equal [filename, lineno], klass.new.method(:find_me_if_you_can).source_location
 
   lineno = __LINE__ + 1
-  klass.define_singleton_method(:s_find_me_if_you_can) {}
+  class <<klass; define_method(:s_find_me_if_you_can) {}; end
   assert_equal [filename, lineno], klass.method(:s_find_me_if_you_can).source_location
 
   klass = Class.new { def respond_to_missing?(m, b); m == :nothing; end }
@@ -243,7 +243,7 @@ assert 'owner' do
 
   assert_equal(c, c.new.method(:foo).owner)
   assert_equal(c, c2.new.method(:foo).owner)
-  assert_equal(c.singleton_class, c2.method(:bar).owner)
+  assert_equal((class <<c; self; end), c2.method(:bar).owner)
 end
 
 assert 'owner missing' do
@@ -413,12 +413,14 @@ assert 'UnboundMethod#bind' do
   assert_equal(:meth, m.bind(1).call)
   assert_equal(:meth, m.bind(:sym).call)
   assert_equal(:meth, m.bind(Object.new).call)
-  sc = Class.new {
-    class << self
+  sc = nil
+  Class.new {
+    sc = class << self
       def foo
       end
+      self
     end
-  }.singleton_class
+  }
   assert_raise(TypeError) { sc.instance_method(:foo).bind([]) }
   assert_raise(TypeError) { Array.instance_method(:each).bind(1) }
   assert_kind_of Method, Object.instance_method(:object_id).bind(Object.new)