Type Alias IsPropertyOptional<U, P>

Determines whether a property P of object type U is declared as optional.

This checks whether the {} type (an empty object) is assignable to Pick<U, P>. In TypeScript, this is true only when P is marked optional using the ? modifier in the type definition.

Importantly, this detects actual optionality rather than checking whether the property's type includes undefined. For example:

type A = { x?: string };               // optional
type B = { x: string | undefined };    // required but allows undefined

IsPropertyOptional<A, "x"> // true
IsPropertyOptional<B, "x"> // false
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