anchor.diff:          )
       let enumValuesByName = new Dictionary<string, EnumValue>()
       let typesByName = new Dictionary<string, CoreVariableType>()
  -    do
  +    let initialize() =
  +        if initialized then () else
  +        initialized <- true
           for definedType in context.Value.DefinedTypes do
               if typesByName.ContainsKey(definedType.TypeName) then
                   invalid <| sprintf "The type ``%s'' is defined more than once" definedType.TypeName
  
positive.code:             })
      static member Default = defaultInstance :> ITypeHandler
  
      member this.ResolveEnumValueByName(name) = enumValuesByName.TryFind(name)
      member this.ResolveVariableTypeByName(name) = typesByName.TryFind(name)
          
      interface ITypeHandler with
          member this.DefinedTypes = context.Value.DefinedTypes
          member this.GetMapping(targetType) =
              let mutable cached = None
              if (not <| mappingCache.TryGetValue(targetType, &cached)) then
                  cached <- context.Value.GetMapping(targetType)
  
negative.code: 
  /// Aggregates a chain of type handlers to support exposing CLR types as GraphQL scalar types.
  type RootTypeHandler(metaHandler : IMetaTypeHandler) as this =
      let mutable initialized = false
      let mappingCache = new Dictionary<Type, TypeMapping option>()
      let context =
          lazy(
  