When I had opened my minecraft 18w18a world, it left me with some materials that were remaining in my inventory, but the world was wiped. When I first found this bug, I thought it was strictly related to the materials remaining in my inventory. However, when I created other tools, those too no longer were able to destroy blocks when using the mine key. As you can imagine, this makes the game completely unplayable and should be taken control of immediately.

Steps to Reproduce:
1) create a minecraft 18w18a world
2) gain sufficient materials to create a tool
3) reopen it in minecraft 18w19a
4) create a tool and attempt to mine a block while damaged