Does a potion of gain strength work if I have mutation resistance?

Question

I have mutation resistance 1 and a potion of gain strength. The latter technically adds a mutation. Logic says it shouldn't work, but it did.

Was I just lucky or gain stat potions work regardless of mutation resistance?

Answer 1

You were lucky, but not that lucky (2/3 chance of success).

Mutation resistance 1 (and mutation resistance 2) grant you a 33% chance of resisting mutations. Mutation resistance 3 grants you a 100% chance of resisting mutations.

Below is the relevant source code:

if (you.mutation[MUT_MUTATION_RESISTANCE]
    && !force_mutation
    && (you.mutation[MUT_MUTATION_RESISTANCE] == 3 || !one_chance_in(3)))
{
    if (failMsg)
        mpr("You feel odd for a moment.");

    return (false);
}