[dart-announce] Dart 1.23 is now available

['Kevin Moore' via Dart Announcements]

Check out the announcement and the changelog!

1.23.0

Strong Mode

• Breaking change - it is now a strong mode error if a mixin causes a name conflict between two private members (field/getter/setter/method) from a different library. (SDK issue 28809).

lib1.dart:

class A {
  int _x;
}

class B {
  int _x;
}

lib2.dart:

import 'lib1.dart';

class C extends A with B {}

    error • The private name _x, defined by B, conflicts with the same name defined by A at tmp/lib2.dart:3:24 • private_collision_in_mixin_application

• Breaking change - strong mode will prefer the expected type to infer generic types, functions, and methods (SDK issue 27586).

  main() {
    List<Object> foo = /*infers: <Object>*/['hello', 'world'];
    var bar = /*infers: <String>*/['hello', 'world'];
  }

• Strong mode inference error messages are improved (SDK issue 29108).

  import 'dart:math';
  test(Iterable/* fix is to add <num> here */ values) {
    num n = values.fold(values.first as num, max);
  }

  Now produces the error on the generic function "max":

  Couldn't infer type parameter 'T'.
  
  Tried to infer 'dynamic' for 'T' which doesn't work:
    Function type declared as '<T extends num>(T, T) → T'
                  used where  '(num, dynamic) → num' is required.
  
  Consider passing explicit type argument(s) to the generic.
  

• Strong mode supports overriding fields, @virtual is no longer required (SDK issue 28120).

  class C {
    int x = 42;
  }
  class D extends C {
    get x {
      print("x got called");
      return super.x;
    }
  }
  main() {
    print(new D().x);
  }

• Strong mode down cast composite warnings are no longer issued by default. (SDK issue 28588).

void test() {
  List untyped = [];
  List<int> typed = untyped; // No down cast composite warning
}

To opt back into the warnings, add the following to the .analysis_options file for your project.

analyzer:
  errors:
    strong_mode_down_cast_composite: warning

Core library changes

• dart:core
  • Added Uri.isScheme function to check the scheme of a URI. Example: uri.isScheme("http"). Ignores case when comparing.
  • Make UriData.parse validate its input better. If the data is base-64 encoded, the data is normalized wrt. alphabet and padding, and it contains invalid base-64 data, parsing fails. Also normalizes non-base-64 data.
• dart:io
  • Added functions File.lastAccessed, File.lastAccessedSync, File.setLastModified, File.setLastModifiedSync, File.setLastAccessed, and File.setLastAccessedSync.
  • Added {Stdin,Stdout}.supportsAnsiEscapes.

Dart VM

• Calls to print() and Stdout.write*() now correctly print unicode characters to the console on Windows. Calls to Stdout.add*() behave as before.

Tool changes

• Analysis

  • dartanalyzer now follows the same rules as the analysis server to find an analysis options file, stopping when an analysis options file is found:
    • Search up the directory hierarchy looking for an analysis options file.
    • If analyzing a project referencing the Flutter package, then use the default Flutter analysis options found in package:flutter.
    • If in a Bazel workspace, then use the analysis options in package:dart.analysis_options/default.yamlif it exists.
    • Use the default analysis options rules.
  • In addition, specific to dartanalyzer:
    • an analysis options file can be specified on the command line via --options and that file will be used instead of searching for an analysis options file.
    • any analysis option specified on the command line (e.g. --strong or --no-strong) takes precedence over any corresponding value specified in the analysis options file.

• Dartium, dart2js, and DDC

  • Imports to dart:io are allowed, but the imported library is not supported and will likely fail on most APIs at runtime. This change was made as a stopgap measure to make it easier to write libraries that share code between platforms (like package http). This might change again when configuration specific imports are supported.

• Pub

  • Now sends telemetry data to pub.dartlang.org to allow better understanding of why a particular package is being accessed.
  • pub publish
    • Warns if a package imports a package that's not a dependency from within lib/ or bin/, or a package that's not a dev dependency from within benchmark/, example/, test/ or tool/.
    • No longer produces "UID too large" errors on OS X. All packages are now uploaded with the user and group names set to "pub".
    • No longer fails with a stack overflow when uploading a package that uses Git submodules.
  • pub get and pub upgrade
    • Produce more informative error messages if they're run directly in a package that uses Flutter.
    • Properly unlock SDK and path dependencies if they have a new version that's also valid according to the user's pubspec.

• dartfmt

  • Support new generic function typedef syntax.
  • Make the precedence of cascades more visible.
  • Fix a couple of places where spurious newlines were inserted.
  • Correctly report unchanged formatting when reading from stdin.
  • Ensure space between - and --. Code that does this is pathological, but it technically meant dartfmt could change the semantics of the code.
  • Preserve a blank line between enum cases.
  • Other small formatting tweaks.

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[Marcelo Siqueira]

Any info about when the chocolatey package for Windows will be available?

Thanks

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[W Chen]

https://www.dartosphere.org/2017/04/24/dart-sdk-and-dartium-1.23.0-chocolatey-packages-for-windows.html