Bug High resistance warrior gets healed from elemental damage

[BattleLord]

This are not a screenshots of a modded or hacked game.

Someone on the discord reported that they were getting healed from death damage, and while at first I was sceptical, after a few tests on my own char, it is clear that this is completely real.
If on a warrior (This is important for some reason, it doesn't work with other classes) you get hit by enemies that deal pure elemental damage while you have a high resistance of that element, you slowly get healed from the attacks.
And on top of that, this healing source also ignores max hp, probably because it was never meant to be a healing source so it doesn't check if it reached the max hp.

I checked it with death and fire, as you can see in the screenshots.
It probably works with other elemental resistances too.

 

[VDX_360]

It's a known issue.

It stems from how Shield Expert reduces projectile damage combined with negative damage.

Shield Expert reduces projectile damage by subtracting damage.
i.e. 7 damage arrow - 4 damage = 3 damage.

However, with high enough elemental resistance, the off-set damage creates a net negative damage, which is treated as health.
I.e. 7 elemental damage is reduced to 1 damage via resistance - 4 damage = -3 damage, which is treated as 3 health.