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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 the first argument to ❰merge❱ must be a record and not some other type.
For example, the following expression is $_NOT valid:
┌─────────────────────────────────────────┐
│ let handler = λ(x : Bool) → x │
│ in merge handler < Foo = True > : True │
└─────────────────────────────────────────┘
⇧
Invalid: ❰handler❱ isn't a record
You provided the following handler:
↳ $txt0
... which is not a record, but is actually a value of type:
↳ $txt1
Some common reasons why you might get this error:
● You accidentally provide an empty record type instead of an empty record when
you ❰merge❱ an empty union:
┌──────────────────────────────────────────┐
│ λ(x : <>) → λ(a : Type) → merge {} x : a │
└──────────────────────────────────────────┘
⇧
This should be ❰{=}❱ instead
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