Yes, the front of a shirt can be re-purposed as a closure for a bag. A great idea from Jude. The snaps fall into the inside of this bag when closed. To make this I cut a piece of shirt front to match my print fabric, lined everything up so that the snaps would be at the top, and sewed everything together so that the shirt front acts as a lining. This is just the right size for keeping my bus knitting projects all together.
This would also work for a bag with a flap. Just playing a bit with possibilities....
This is a pillow cover I did several years ago. For this one I sewed just the front edge of the shirt to other pieces of fabric to make a "pieced" backing.
The shirt fronts I've used here are from some of my grandfather's work shirts.