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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❱