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).

A stronger Dart for everyone

We are constantly asking ourselves:
How do we make developers even more productive when writing Dart apps? We believe that a critical part of the answer to this question is to make strongmode – a sound static type system for Dart – the standard for all Dart developers.

Teams that use Dart to build apps like Soundtrap, AdWords, AdSense, and Greentea say they really enjoy using strong mode features, such as early error detection. In fact, teams that have switched completely to strong mode cite not only early error detection but also better code readability and maintainability as major benefits. We hear this both from small teams and Рeven more so Рfrom large teams with hundreds of developers writing and maintaining millions of lines of Dart code. As Björn Sperber from Soundtrap says,
Strong mode and the smooth integration with IntelliJ is a joy to use and a huge improvement. If you’ve tried out Flutter, you’ve already used strong mode checks from the Dart analyzer.

Given the benefits …

AngularDart 3.0: Easy upgrade, better performance

AngularDart 3.0 is now available. It brings better performance and smaller generated code, while also making you more productive.


Version 3.0 is an evolution: although it has some breaking changes (detailed below), it is a smooth upgrade due to minimal public API adjustments. Most of the progress is under the hood—in code quality, stability, generated code size, performance, and developer experience.

Code quality:
2731 instances of making the framework code more type safe (using sound Dart).The AngularDart framework code size is down by 12%.Many additional style updates to the codebase:Changed to use idiomatic <T> for generic methods.Removed NgZoneImpl, all the code exists in NgZone now.Stability:
Many CSS encapsulation fixes due to update with csslib package.Fixed bugs with IE11.

Performance:
For the Mail sample app, we see 30% faster time-to-interactive (currently 3812 ms on a simulated 3G connection, measured via Lighthouse).Our large app benchmark shows 2x faster render times of…