Generate built-in `Range`

Hi! 👋 Was thinking of adding a built-in generator of the System.Range struct, as this would expand the default generator functionality. Am currently using this:

let range = gen {
  let! min = Gen.choose (0, Int32.MaxValue)
  let! max = Gen.choose (min, Int32.MaxValue)
  return Range (min, max) }

To make sure that the minimum is always lower than the maximum. But, with some additional options, one could include Range.StartAt and Range.EndAt too.

Just a suggestion when using the awesome FsCheck library 😉 .

[kurtschelfthout]

Maybe an idea to create an extra generator that generate the built-in System.Range from an Interval?

Yeah I think that makes sense. Or even extract the code and parametrize the contructor, could be slightly faster without creating an intermediate type.

For standard types like System.Range I think it certainly makes sense to have them built-in.

[stijnmoreels]

Great! Happy to pick this up, but the supported frameworks on the main project are still not in the range where the System.Range is supported (net452;netstandard2.0;netstandard1.6;netstandard1.0) so maybe this could be set up on-hold till we update FsCheck towards .NET 6.