Nice try, but no cookie

Elijah, picking at his lunch very pokily, was left alone at the table with instructions to finish his last few bites before helping himself to a cookie. A few minutes later he comes running to me in another room to report: "I all done! Now I have cookie?"
Me: "Put your dishes in the dishwasher, then you may get a cookie."
Elijah: "Okay! I put dishes in dishwasher and food in garbage and get cookie!"
Me: "Um, you said you ate all your food. Is there still some on your plate?"
Elijah: "Um...."
Trapped in his own little lie of helpfulness. Nice try buddy, but no cookie yet.