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Ok, but if you have a coworker who's going to maliciously overload operators to behave differently than expected, then all bets are off and you have much bigger problems than how to check for null.

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Its not malicious or unheard of. Unity, a very popular game engine, overloads the == operator as well as the implicit boolean cast for their built in types. They do this because their types adhere to a specific lifecycle. When an object is dead, == null is true.

I'm not a fan and its not super common but it happens.

I was half joking, obviously this is hopefully not done out of malice and hopefully whoever overloads the operator still handles the case != null logically equal to the expected way. There could be smaller differences than true correctness like performance too, not least since the != will be a virtual call that must be resolved, and also the overloaded implementation may or may not be as efficient as “is not null” is.

This is a similar same issue as the “what’s wrong with using String instead of string” when it only breaks if someone adds their own type and calls it String, or aliases a type to String (with a capital S). This actually happens in actual code bases for various reasons not necessarily malicious.

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