Fix setting method visibility on method wrapped with prepend

Ignore prepended modules when looking for already defined methods on a
class to set the visibility on.
[Fix GH-1834]

From: Dylan Thacker-Smith <Dylan.Smith@shopify.com>

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@62725 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

spec/ruby/core/module/private_spec.rb

@@ -51,4 +51,43 @@ describe "Module#private" do
       Module.new.send(:private, :undefined)
     end.should raise_error(NameError)
   end
+
+  it "only makes the method private in the class it is called on" do
+    base = Class.new do
+      def wrapped
+        1
+      end
+    end
+
+    klass = Class.new(base) do
+      def wrapped
+        super + 1
+      end
+      private :wrapped
+    end
+
+    base.new.wrapped.should == 1
+    lambda do
+      klass.new.wrapped
+    end.should raise_error(NameError)
+  end
+
+  it "continues to allow a prepended module method to call super" do
+    wrapper = Module.new do
+      def wrapped
+        super + 1
+      end
+    end
+
+    klass = Class.new do
+      prepend wrapper
+
+      def wrapped
+        1
+      end
+      private :wrapped
+    end
+
+    klass.new.wrapped.should == 2
+  end
 end

test/ruby/test_module.rb

@@ -1887,6 +1887,25 @@ class TestModule < Test::Unit::TestCase
     assert_raise(ArgumentError) { Module.new { prepend } }
   end
 
+  def test_prepend_private_super
+    wrapper = Module.new do
+      def wrapped
+        super + 1
+      end
+    end
+
+    klass = Class.new do
+      prepend wrapper
+
+      def wrapped
+        1
+      end
+      private :wrapped
+    end
+
+    assert_equal(2, klass.new.wrapped)
+  end
+
   def test_class_variables
     m = Module.new
     m.class_variable_set(:@@foo, 1)

vm_method.c

@@ -1054,8 +1054,9 @@ rb_export_method(VALUE klass, ID name, rb_method_visibility_t visi)
 {
     rb_method_entry_t *me;
     VALUE defined_class;
+    VALUE origin_class = RCLASS_ORIGIN(klass);
 
-    me = search_method(klass, name, &defined_class);
+    me = search_method(origin_class, name, &defined_class);
     if (!me && RB_TYPE_P(klass, T_MODULE)) {
 	me = search_method(rb_cObject, name, &defined_class);
     }
@@ -1068,7 +1069,7 @@ rb_export_method(VALUE klass, ID name, rb_method_visibility_t visi)
     if (METHOD_ENTRY_VISI(me) != visi) {
 	rb_vm_check_redefinition_opt_method(me, klass);
 
-	if (klass == defined_class || RCLASS_ORIGIN(klass) == defined_class) {
+	if (klass == defined_class || origin_class == defined_class) {
 	    METHOD_ENTRY_VISI_SET(me, visi);
 
 	    if (me->def->type == VM_METHOD_TYPE_REFINED && me->def->body.refined.orig_me) {