how do i prevent non-nullable types in arguments

so we have the following convenience function:

export function asDefinedOr<T, D>(value: T | undefined, defaultValue: D): T | D { return value !== undefined ? value : defaultValue; }

we would like to prevent the following from happening

declare var x : number; asDefinedOr(x, 0); // <-- problem, unnecessary call, because x cannot be undefined

so we would like to make only T | undefined types allowed as aguments but not just T

is there a way to do it using conditional types?

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