ddc does not respect classes emulating functions in dart

[jacob314]

https://www.dartlang.org/articles/emulating-functions/

Repro:

typedef WindowClickHandler(Object e);

class DefaultWindowClickHandler {
  void call(Object e) { }
}

WindowClickHandler h = new DefaultWindowClickHandler(); 
// Generates an error as DefaultWindowClickHandler is not a WindowClickHandler

[jacob314]

Another example from Angular

class ExceptionHandler {

 /**
  * Delegate uncaught exception for central error handling.
  *
  * - [error] The error which was caught.
  * - [stack] The stacktrace.
  * - [reason] Optional contextual information for the error.
  */
  call(dynamic error, dynamic stack, [String reason = '']) {
    print("$error\n$reason\nSTACKTRACE:\n$stack");
  }
}

DDC:severe: StaticTypeError, Type check failed: exceptionHandler: _exceptionHandler (ExceptionHandler) is not of type (dynamic, dynamic) → void

    count = rootWatchGroup.detectChanges(
        exceptionHandler: _exceptionHandler,
        changeLog: changeLog,
        fieldStopwatch: _scopeStats.fieldStopwatch,
        evalStopwatch: _scopeStats.evalStopwatch,
        processStopwatch: _scopeStats.processStopwatch);

[vsmenon]

Leaf has some todos for this case in rules.dart.