anchor.diff:  
       let head (q : IQueryable<'a>) =
           q.First()
  -
  +    let headTask (q : IQueryable<'a>) =
  +        q.FirstAsync()
       let headAsync (q : IQueryable<'a>) =
  -        q.FirstAsync()
  -        |> Async.AwaitTask
  +        q
  +        |> headTask
  +        |> Async.AwaitTask
  +
   
       let map (f : Quotations.Expr<'a -> 'b>) (q : IQueryable<'a>) =
           f
  
positive.code: 
      let exactlyOne (q : IQueryable<'a>) =
          q.Single()
      let exactlyOneAsync (q : IQueryable<'a>) =
          q.SingleAsync()
          |> Async.AwaitTask
  
      let filter (f : Quotations.Expr<'a -> bool>) (q : IQueryable<'a>) =
  
negative.code:             let func = Lambda.ofArity1 part
              pExpr.Increment(func, inc)
  
  module Queryable =
  
      open System.Linq
  