What would happen if a Pokemon dealt negative damage?

Question

While the damage calculation doesn't have any negatives, what would happen if any of the values were negative?

• Is the damage set to 1?

• Does it underflow to a really big number?

As a follow up, what if they were zero?

Comments

How would one test this?

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Not an answer but similar. In gen 1, when receiving/giving negative damage, the move fails.