Select sub-type for exhaustive check. E.g. .exhaustive(([state, event]) => event.type)

[audunolsen]

The docs' reducer example and its usage of exhaustive doesn't seem that helpful. When matching a complex data type like a tuple consisting of two unions with 4 entries each, a true exhaustive check would need to handle 16 possible combinations. Explicitly handling all those cases wouldn't be meaningful. As the docs state:

only a subset of these events make sense for each given state

What is actually happening in the example is that each value for event.type is manually exhaustively checked. If you add a new event type in the given reducer example then there would be no ts error indicating you need to handle a new event type.

It would be extremely helpful to select a subtype of the matched pattern which should be exhaustively checked.

E.g. something like

match([state, event]).exhaustive(([state, event]) => event.type)

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Amazing work! 🌟 Happy new year