What is the problem with a complicated union type in TypeScript?

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The problem with a complicated union type in TypeScript is that it can become difficult to understand and maintain. As the number of types in the union increases, it becomes harder to reason about the possible values and potential code paths. Additionally, some advanced type features may not be supported with a complex union type, which can limit the flexibility of code using it. Finally, a complicated union type may lead to more verbose code and may require additional type annotations, which in turn can increase cognitive load and reduce code readability.