Skip to main content

Notes from 5/14 Dart language meeting

Posted by Bob Nystrom


Once a week, Lars, Gilad, and Kasper meet to discuss the design of the language. For your delight and edification, here are my notes from this week's meeting:

var and Dynamic

We see people using Dynamic as a type argument even when they don't have to. Also see people trying to use var as a type argument. Gilad said there are very few cases where you actually do need to use Dynamic.

The source of the confusion is that var is used in a place (local variable declaration) where you can also use a type to declare a variable, so it makes people think var is itself a type.

He proposed always requiring var to declare variables to clarify that:

  var int foo = 123;

but doesn't think it will be liked.

Alternately, we could follow users' intuition and allow var to be used like a type:

  var map = new Map<int, var>();

Gilad is worried allowing var anywhere a type can appear may have some unpleasant corner cases we aren't thinking of. He likes the current behavior because he knows it is non-problematic.

No decision was reached.

I asked if when a user declares a variable with var are is the intent they are stating that they don't care what the variable's type is, or that they do care and want it to be dynamic? Gilad said from the language's point of view, it doesn't matter because there is no difference.

Re-export

Agreed to have an "export" parameter in #import directives. So to re-export, you do:

  #import('somelib.dart', export: true);

If you want to use a library internally but only re-export a subset of its names, you would do:

  #import('somelib.dart');
  #import('somelib.dart', show: ['foo', 'bar'], export: true);

One consideration is how this works with prefixes. If you re-export something you imported with a prefix, does the prefix compound?

The current answer to keep the semantics restricted is "no". Prefixes are for using a name internally, and do not affect how it gets exported.

Cast syntax

Our hangout flaked out and Gilad dropped off for a few minutes. In that interim, we briefly discussed an explicit cast syntax.

Kasper pointed out that if you want to support an optional second type system that doesn't allow implicit downcasts, you'll need some kind of cast syntax. Lars says "as" is probably a good idea.

Statics on interfaces

Lars does not like code appearing in interfaces. Kasper says default classes are confusing for people, and that in large interfaces, people don't see that the constructors are there.

We talked briefly about constructors in interfaces just working like factory constructors so that you wouldn't need "default" to do the delegation.

Lars had to leave at this point. I don't think there was a firm decision, but it seems like we do not intend to support static methods defined directly in interfaces but may support them by delegating to the default class.

Directives

Kasper mentioned that we may want to refresh the directive syntax at some point. Users don't seem to like it. Gilad favors dedicated syntax for imports.

Cheers!

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).

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…

AngularDart 2.1 and new Components

AngularDart got its own dedicated team 5 months ago. Last month, we launched 2.0 final on the Dart Developer Summit. Today, we’re releasing the first minor release after that: 2.1.

Since the focus of AngularDart is Productivity, Performance, Stability, there are no major breaking changes (see the changelog) — but a lot of behind-the-scenes improvements. Your apps will get slightly smaller and faster (even relative to 2.0 which already made huge strides in size and performance since the compiled-from-TypeScript days).

Many features that AngularJS had to implement for JavaScript and TypeScript are not needed in Dart (because Dart already has those features out-of-the-box). So we’re removing them from AngularDart. Renderer is deprecated in favor of plain-old dart:html. NgPlural is going away — Dart programs can use the package:intl library.

New components

On the Dart Developer Summit, we launched AngularDart Components — the material design widgets Google is using in customer-facing apps …