What I expected to happen: the leaf block would suffocate me or not let me see through it.

What actually happened: the leaf block gave me xray, allowing me to see caves and dungeons
Steps to Reproduce:
1. Dig a two block long, one block wide, and 2 blocks deep hole.
2. Place down rails and a minecart on one of the blocks you just dug down to.
3. place a leaf block directly above the minecart.
4. get into the minecart, and you should be given Xray.