anchor.diff:              let results = PerfTest.run tester tests
               () // TODO: handle saving of results
   
  -    let testPerfCompare = testPerfCompareWithConfig CompareConfig.Defaults
  +    let testPerfCompare<'a when 'a :> ITestable> name (subj : 'a) (alts : 'a list) (tests : 'a PerfTest list) =
  +        testPerfCompareWithConfig CompareConfig.Defaults name subj alts tests
   
       let testPerfHistoryWithConfig config name =
           ()
  
positive.code:     open Fuchu.Impl
  
      type PerfConfig =
          {  }
  
      type CompareConfig =
          { throwOnError : bool
  
negative.code:         ()
  
  module Usage =
      open global.PerfUtil
  
      module Types =
          type Y = { a : string; b : int }
          type X = { c : Nullable<int>; d : uint64 }
  
      type Serialiser =
          inherit ITestable
          abstract member Serialise<'a> : 'a -> unit
  
      type SlowSerialiser() =
  