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Explanation: You can ❰merge❱ the alternatives of a union using a record with one
handler per alternative, like this:
┌─────────────────────────────────────────────────────────────────────┐
│ let union = < Left = +2 | Right : Bool > │
│ in let handlers = { Left = Natural/even, Right = λ(x : Bool) → x } │
│ in merge handlers union : Bool │
└─────────────────────────────────────────────────────────────────────┘
... but you must provide exactly one handler per alternative in the union. You
cannot supply extra handlers
For example, the following expression is $_NOT valid:
┌───────────────────────────────────────┐
│ let union = < Left = +2 > │ The ❰Right❱ alternative is missing
│ in let handlers = │
│ { Left = Natural/even │
│ , Right = λ(x : Bool) → x │ Invalid: ❰Right❱ handler isn't used
│ } │
│ in merge handlers union : Bool │
└───────────────────────────────────────┘
You provided the following handlers:
↳ $txt0
... which had no matching alternatives in the union you tried to ❰merge❱
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