anchor.diff:                      new RangeGeneratorEnumerator<'T>(start, endInclusive, advance) :> IEnumerator<'T>
           }
   
  +    /// Support for makeOptionalRange<'T>.
       type RangeGeneratorEnumeratorWithOption<'T when 'T :> IComparable<'T> and 'T : comparison>
                       (start: 'T
                      , endInclusive: 'T
  
positive.code: 
              member __.Reset(): unit = state <- BeforeFirstOption
  
      let inline makeOptionalRange<'T when 'T :> IComparable<'T> and 'T : comparison>
                  (start: 'T)
                  (endInclusive: 'T)
  
negative.code:                 member __.GetEnumerator(): IEnumerator<'T option> =
                      new RangeGeneratorEnumeratorWithOption<'T>(start, endInclusive, advance) :> IEnumerator<'T option>
          }
  