anchor.diff:          Gen.oneof
               [
                   Gen.map3 (fun b expr1 expr2 -> SynExpr.Sequential(SequencePointsAtSeq, b, expr1, expr2, zero)) Arb.generate<_> genSubDeclExpr genSubSeqExpr
  -                Gen.map3 (fun b bindings expr -> SynExpr.LetOrUse(b, not b, bindings, expr, zero)) Arb.generate<_> generateSynBindingList genSubBasicExpr
  +                // Should not have 'use' keywords on the top level
  +                Gen.map3 (fun b bindings expr -> SynExpr.LetOrUse(b, false, bindings, expr, zero)) Arb.generate<_> generateSynBindingList genSubBasicExpr
               ]
   
   and generateDeclExpr size =
  
positive.code:     | [] -> 
          stdout.WriteLine("Can't shrink {0}", sprintf "%A" input)
          Seq.empty
      | exprs -> 
          let (Input source) = input
          Seq.collect collectSynExpr exprs 
          |> Seq.map (fromExprRange source)
          |> Seq.distinct
  
  type Generators = 
  
negative.code:         |> Seq.toArray
      let startIndex = positions.[r.StartLine-1] + r.StartColumn
      let endIndex = positions.[r.EndLine-1] + r.EndColumn-1
      let sample = source.[startIndex..endIndex]
      // Avoid to recreate the same source
      // because it may cause the shrinker to loop forever
      if (sample.Trim()) = (originalSource.Trim()) then 
          None
      else Some (Input sample)
  
  let toSynExprs (Input s) =
      match (try Some (parse false s) with _ -> None) with
  