[RFC] @unboxed NaN and infinities

Development
1

Forgetting to handling NaN and infinities is a common problem when working with floating point numbers. In order to make it easier to handle all cases, we should allow for these unboxed values:

@unboxed
type t =
  | @as(nan) NaN
  | @as(positiveInfinity) PositiveInfinity
  | @as(negativeInfinity) NegativeInfinity
  | Finite(float)

// example usage
let value = switch value {
| NaN => raise(...)
| PositiveInfinity => Core.Float.Constants.maxValue
| NegativeInfinity => Core.Float.Constants.minValue
| Finite(value) => value
}

Considering finite floats can already be used unboxed, this seems like a logical addition.

There could be complexity due to compiling to isNaN and isFinite instead of a simple number comparison, but the unboxed JSON type already uses Array.isArray, so it should be doable.

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