Since adding this validation we've already changed our inference to use knowledge from manual memoization to inform when values are frozen and which values are non-nullable. To align with that, if the user chooses to use different optionality btw the deps and the memo block/callback, that's fine. The key is that eg `x?.y` will invalidate whenever `x.y` would, so from a memoization correctness perspective its fine. It's not our job to be a type checker: if a value is potentially nullable, it should likely use a nullable property access in both places but TypeScript/Flow can check that.
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