use cocoa::base::id;

pub trait MTLCommandBuffer {
    fn renderCommandEncoderWithDescriptor(self, renderPassDescriptor: id) -> id;
}

impl MTLCommandBuffer for id {

}

use cocoa::base::id;

pub trait MTLCommandBuffer {

}

impl MTLCommandBuffer for id {

}

--- 
+++ 
@@ -1,7 +1,7 @@
 use cocoa::base::id;
 
 pub trait MTLCommandBuffer {
-
+    fn renderCommandEncoderWithDescriptor(self, renderPassDescriptor: id) -> id;
 }
 
 impl MTLCommandBuffer for id {
Add MTLCommandBuffer::renderCommandEncoderWithDescriptor to MTLCommandBuffer trait def
