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 second argument to ❰merge❱ must be a union and not some other type.

For example, the following expression is $_NOT valid:


    ┌──────────────────────────────────────────┐
    │ let handlers = { Foo = λ(x : Bool) → x } │
    │ in  merge handlers True : True           │
    └──────────────────────────────────────────┘
                         ⇧
                         Invalid: ❰True❱ isn't a union


You tried to ❰merge❱ this expression:

↳ $txt0

... which is not a union, but is actually a value of type:

↳ $txt1