How to use the Generics in the top-level function?

[vvakame]

Hello there.

I want to know about how to write a top-level function with generics.

I'm writing a Testing-Framework for Dart. ( https://github.com/vvakame/teaolive/blob/1b8adcfad1ca069f97cb780d7c3640af15878cde/example/sample_test.dart#L5 )

I want to my library provide about type-safe test case.

for example.

expect("foobar").toBe(777); // error on compile-time. String is not int.

now, I wrote a this code.

Expection expect(var obj){

  return new _ExpectionImpl.expect(obj);

}

However, I want to write like this!

Expection<T> expect(T obj){

  return new _ExpectionImpl.expect(obj);

}

expect("hoge").toBe("hoge");

                 ↑ return 'Expection<String>' type.

but I can't done it.

Do you know a some solutions? I need a some advice.

real code is here.

https://github.com/vvakame/teaolive/blob/1b8adcfad1ca069f97cb780d7c3640af15878cde/libs/teaolive.dart#L61

regards.

[Ladislav Thon]

I want to know about how to write a top-level function with generics.

Dart doesn't have generic functions, so this isn't possible right now. You can star http://dartbug.com/254.

And BTW:

expect("foobar").toBe(777); // error on compile-time. String is not int.

Even if Dart had generic functions and expect would be one, this will never be a compile-time error. It would only fail at runtime in checked mode. Dart is a dynamically typed language in its heart, and type annotations mostly serve as a documentation (and programmers are encouraged to run their programs in checked mode, which checks these type annotations and fail at runtime when types don't match).

LT

[vvakame]

Thank you for your advice.

Dart doesn't have generic functions, so this isn't possible right now. You can star http://dartbug.com/254.

I just added a star now. I hope this feature to be implemented.

 

Even if Dart had generic functions and expect would be one, this will never be a compile-time error. It would only fail at runtime in checked mode. Dart is a dynamically typed language in its heart, and type annotations mostly serve as a documentation (and programmers are encouraged to run their programs in checked mode, which checks these type annotations and fail at runtime when types don't match).

Oh, is that so. I didn't know that checked mode works with type annotations.

I need a warning on the DartEditor; raise warning from code-analyzer if type mismatched. I'm writing a comment to Issue 254.

Regards.

2012年5月14日月曜日 16時06分38秒 UTC+9 Ladislav Thon: