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Dart 1.23: Better strong mode support

Dart 1.23 is now available. It introduces support for overriding fields in strong mode and a lot of other improvements. Get it now!

Screen Shot 2017-04-21 at 16.15.20.png
Figure 1: Overriding fields in strong mode

We have been spending a lot of our time on our unified front-end (explained by Vyacheslav Egorov in this short talk from the Dart Developer Summit). We're also doing a lot of work to support our critical customers (for example, Flutter gets better Windows support with this release) and solidifying strong mode.

Some notable changes in this release:
  • Overriding fields is now supported in strong mode. You don’t need to tag them with @virtual anymore.
  • Strong mode inference error messages are more helpful.
  • Strong mode now prefers the expected type to infer generic types, functions, and methods.
  • The UriData.parse method now normalizes and validates its input better.
  • Importing dart:io is now allowed in the browser, as a stopgap measure to make it easier to write libraries that share code between platforms (like package http that needs to run in the browser, on mobile, and on the command line).
  • pub publish now warns you when you’re importing a package that is not a direct dependency in pubspec.yaml.
  • pub get/upgrade now produces a more informative error message for Flutter.
  • dartfmt now makes precedence of cascades more visible, and adds other small formatting tweaks.
  • Fixes for Unicode character printing in the Windows console, inconsistencies between dartanalyzer and the analysis server in finding the options file, pub “UID too large” errors on OS X, and more.
For more information, see the changelog.

Please download the latest release and let us know what you think!

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Const, Static, Final, Oh my!

Posted by Seth Ladd

(This is an "oldie but a goodie" misc@dartlang.org post originally written by Bob Nystrom. It is being posted here as the explanations still ring true.)

Bob writes:


"static", "final", and "const" mean entirely distinct things in Dart:

"static" means a member is available on the class itself instead of on instances of the class. That's all it means, and it isn't used for anything else. static modifies *members*.

"final" means single-assignment: a final variable or field *must* have an initializer. Once assigned a value, a final variable's value cannot be changed. final modifies *variables*.

"const" has a meaning that's a bit more complex and subtle in Dart. const modifies *values*. You can use it when creating collections, like const [1, 2, 3], and when constructing objects (instead of new) like const Point(2, 3). Here, const means that the object's entire deep state can be determ…