Skip to main content

Dec 10 Language Design Meeting Notes

Dart engineer Bob Nystrom has posted the notes from the December 10th language design meeting. He writes:

Mixins

We're down to arguing about syntax. Lars says, OK, here it is:

    class C extends S with M1, M2 { ... }

Mixins are linearized from right to left. This makes sense since the class body appears last but takes precedence, so we work backwards from that. Gilad has an updated proposal that he'll send out.

There is one corner case. If you want to mixin, you have to have an explicit superclass:

    class C extends Object with M1 { ... }

[Bob: This means that I believe we have the semantics and syntax for mixins nailed down now. Woo!]

throw as expression

They're looking to implement this in dart2js now. Even with the restriction on rethrows, it still feels tricky. Since throw takes an arbitrary expression on the right, including a conditional one, there are some corner cases related to how it binds.

Lars: Is rethrow an expression?
Gilad: It is in the spec, but the implementations don't support it.
Kasper: It is hard to parse. We have to lookahead to tell if we're at the beginning of an expression.
Lars: Let's make both kinds of throws an expression and rename rethrow to use a "rethrow" contextual keyword. It's a rarely used feature. Better?
Gilad: I'll talk to the implementors and work through something.

Metadata in corelib

Brian: There is a faction that says certain metadata constructs need to be in the language spec before they can be put into the core library. Are all tools required to have certain behavior because certain metadata is in the core library? For example, does dart2js have to emit some kind of notification if you use @deprecated?

Gilad: If we want metadata that does something magical then it should be in the spec. If it's just in tools, we shouldn't.

[Bob: I think an example of an annotation with magic behavior is one that says "don't tree-shake this".]

Kasper: If we use them in our libraries, we have to tell people what they mean. So it has to be specified somewhere, even if informally.

Gilad: Sure, but that applies to the library API itself too. You have to document it.

Lars: I would like to minimize the use of annotations in core library. We don't want using them to be part of normal style. Java uses them everywhere.

Configuration-specific code

Lars suggests we could have annotation to put on constants that lets you override its value from the outside from something like a command line argument.

We'll discuss this more after M2.

Cheers!

As always, we invite you to join our Dart mailing list, ask questions on Stack Overflow, or file feature requests on dartbug.com.

Popular posts from this blog

Dart in 2016: The fastest growing programming language at Google, 2nd fastest growing in TIOBE Index

Dart was the fastest growing programming language at Google in 2016 with millions of lines of code written. It also made it to TIOBE Index Top 20 this month (see TIOBE's methodology).

It takes time to build something as ambitious as Dart and, in some ways, Dart is still in its infancy. But we're glad the hard work is starting to pay off.

Many thanks to our amazing community!

We're going to celebrate by ... releasing 1.22 next week (as per our usual 6 week release schedule).

AngularDart is going all Dart

Until now, the multiple language flavors of Angular 2 were written as TypeScript source, and then automatically compiled to both JavaScript and Dart. We're happy to announce that we’re splitting the Angular 2 codebase into two flavors – a Dart version and a TypeScript/JavaScript version – and creating a dedicated AngularDart team.

This is amazing news for Dart developers because:

The framework will feel more like idiomatic Dart.It will make use of Dart features that couldn't work with the TypeScript flavor. It will be faster.
This is equally great news for our TypeScript and JavaScript developers, by the way. Cleaner API, performance gains, easier contributions. Read more on the Angular blog.

Angular 2 for Dart is used by many teams at Google. Most famously by the AdWords team, but many other Google teams build large, mobile-friendly web apps. Some of the top requests from these teams were: make the API feel like Dart, provide a faster edit-refresh cycle, and improve applicat…

The new Google AdSense user interface: built with AngularDart

AdSense is a free, simple way to earn money by placing ads on your website. The team just launched a completely new version of their app for publishers. Read all about it here. We asked Daniel White, the tech lead for the project, some questions because the new UI happens to be built with Dart and Angular2.


AdSense launched way back in 2003. How long is it since the last big redesign?
Last big redesign was called ‘AdSense 3’ and launched about 6 years ago. It was written in Google Web Toolkit (GWT) and the UI has evolved through several iterations - but this is the first ground-up redesign in 6 years. There are a number of long-standing UX issues that we’ve taken the opportunity to solve. A big shout-out to our UX team who’ve been 100% behind this project. We couldn’t have done it without them!

How many software engineers worked on the project?
Purely on the AdSense applications, we have a team of close to 100. Around 25% of them write Dart.

How many lines of code?
We have around 160K LO…