1 files changed, 24 insertions, 3 deletions
diff --git a/activesupport/lib/active_support/core_ext/object/extending.rb b/activesupport/lib/active_support/core_ext/object/extending.rb
index 7c79d73f21..19f42cabce 100644
--- a/activesupport/lib/active_support/core_ext/object/extending.rb
+++ b/activesupport/lib/active_support/core_ext/object/extending.rb
@@ -42,10 +42,31 @@ class Object
       values
     end
   end
-  
+
   unless defined? instance_exec # 1.9
-    def instance_exec(*arguments, &block) #:nodoc:
-      block.bind(self)[*arguments]
+    module InstanceExecMethods #:nodoc:
+    end
+    include InstanceExecMethods
+
+    # Evaluate the block with the given arguments within the context of
+    # this object, so self is set to the method receiver.
+    #
+    # From Mauricio's http://eigenclass.org/hiki/bounded+space+instance_exec
+    def instance_exec(*args, &block)
+      begin
+        old_critical, Thread.critical = Thread.critical, true
+        n = 0
+        n += 1 while respond_to?(method_name = "__instance_exec#{n}")
+        InstanceExecMethods.module_eval { define_method(method_name, &block) }
+      ensure
+        Thread.critical = old_critical
+      end
+
+      begin
+        send(method_name, *args)
+      ensure
+        InstanceExecMethods.module_eval { remove_method(method_name) } rescue nil
+      end
     end
   end
 end