Potions while in drink

Drinking a potion and fastly converting to another potion while drinking it will overlay on the other potion steps to preduse:
1-bring two types of potions for example : 1st potion is swiftness
2nd potion is leaping
2-try drinking one of the two lets say you drank the swifness
3-while drinking the swiftness fastly press on the leaping in your hotbare
4-the swiftness will overlay on the leaping meaning that leaping will disapear and swifness will duplicate
What i expected was the while drinking swifness and converting to leaping the player will stop drinking swiftness and start drinking leaping wish i helped out thx alot for hard working