Using Gems to Buy More Loot for Upgrades Even Though The Storages are Full?

For example, I have 10k dark elixir and x gems as long its enough to buy another 2.5k dark elixir so I can upgrade my Barbarian King to level two. My storage is currently at level one, which means that it can only hold 10k, which is not enough to hold the 12.5k dark elixir necessary to upgrade my Barbarian King.

So my question is, when the game asks me if I want to buy more dark elixir to have enough for the upgrade, if I do buy the remaining 2.5k dark elixir, will the game let me or will it not and ask me to upgrade my storage instead?

I was unable to find sources on the internet to test this, but with personal tests I can prove that you cannot purchase more resources than your storages.

First the store can only allow you buy % of your total storage: Secondly, when you try to purchase more loot than what you have it will say Build Or Upgrade Existing <Type of Storage> Storages!