The new weapon Mace has some bugs related to enchantments.
Even though it has durability, mending, unbreaking cannot be enchanted through anvil.
In addition, Curse of Vanishing also cannot be enchanted on mace. 

Enchanting mace in creative mode is possible, but enchanting it in survival mode with anvil is not working. 
Since it has durability, and it is a weapon, I believe this is a bug that need to be resolved in further snapshots!