anchor.diff:  
                       match ptdT.GetConstructors(bindAll) |> Seq.tryPick (function :? ProvidedConstructor as pc when pc.IsTypeInitializer -> Some pc | _ -> None) with
                       | None -> ()
  +                    | Some _ when ptdT.IsInterface ->
  +                        failwith "The provided type definition is an interface; therefore, it may not provide constructors."
                       | Some pc ->
                           let cb = ctorMap.[pc]
                           let ilg = cb.GetILGenerator()
  
positive.code:                             [ for v in parameterVars -> Expr.Var v ]
  
                          match pminfo.GetInvokeCode with
                          | Some invokeCode ->
                              let expr = invokeCode parameters
  
  
negative.code:                             let expectedState = if (transType minfo.ReturnType = ILType.Void) then ExpectedStackState.Empty else ExpectedStackState.Value
                              let codeGen = CodeGenerator(assemblyMainModule, genUniqueTypeName, implicitCtorArgsAsFields, convTypeToTgt, transType, transFieldSpec, transMeth, transMethRef, transCtorSpec, ilg, methLocals, parameterVars)
                              codeGen.EmitExpr (expectedState, expr)
                          ilg.Emit I_ret
                        | _ -> ()
  
  