| # Copyright (c) 2019, the Dart project authors. Please see the AUTHORS file |
| # for details. All rights reserved. Use of this source code is governed by a |
| # BSD-style license that can be found in the LICENSE file. |
| |
| # Experimental features are described in docs/process/experimental-flags.md |
| # (Despite the name, they are not really intended for experiments.) |
| # They are intended to enable new features or enhancements that are being |
| # developed and are not yet shipped. Experimental feature flags are expected |
| # to be relatively short-lived. |
| # |
| # ### Code Generation |
| # |
| # When you change this file, run the following to update analyzer, kernel, and |
| # vm: |
| # |
| # analyzer: |
| # dart pkg/analyzer/tool/experiments/generate.dart |
| # |
| # kernel: |
| # pkg/front_end/tool/fasta generate-experimental-flags |
| # |
| # vm: |
| # dart tools/generate_experimental_flags.dart |
| # |
| # ### Overview |
| # |
| # This document consists mostly of a map called "features". |
| # Each entry in this map corresponds to an experiment, |
| # and contains the following parts: |
| # |
| # 1. help: (required text) |
| # A human readable description of the experiment. |
| # |
| # 2. enabledIn: (optional #.#) |
| # The Dart SDK version (<major>.<minor>) in which the experiment is shipping. |
| # |
| # If this field is specified, then the experiment is enabled regardless of |
| # the actual version of the SDK. If this field is omitted, then the |
| # experiment is disabled by default, but may be enabled by specifying the |
| # flag on the command line. (e.g. --enable-experiment=non-nullable) |
| # |
| # A version less than this version may be specified in a .packages file |
| # or in a library language version override (e.g. // @dart = 2.1) |
| # to disable this feature. For more on library language version override, see |
| # https://github.com/dart-lang/language/blob/master/accepted/future-releases/language-versioning/language-versioning.md |
| # |
| # 3. expired: (optional boolean) |
| # If true, then the experiment can no longer be enabled by specifying the |
| # flag on the command line, and the corresponding entry is slated for |
| # eventual removal from this file. If this field is omitted, then 'expired' |
| # is considered to be false. |
| # |
| # 4. validation: (optional string) |
| # If provided this should be a program that prints "feature enabled" on |
| # stdout if the feature is enabled, and throws or fails to compile otherwise. |
| # The intended use for this is to be able to run generic tests for each |
| # experiment. |
| # |
| # Using the above fields, experiments pass through several states: |
| # |
| # Disabled: |
| # When an experiment is first added to this file, the 'enabledIn' and |
| # 'expired' fields are omitted and the experiment is disabled by default, |
| # but may be enabled by specifying the flag on the command line. |
| # The implementation teams begin building support for the feature, |
| # guarded by the flag. Users can enable the flag and begin to try out |
| # the feature as it is being developed. |
| # |
| # Experimental release: |
| # When an experiment is released, then the 'experimentalReleaseVersion' field |
| # is added indicating which version of the SDK contains this new language |
| # feature for libraries and packages in mentioned in |
| # `sdk/lib/_internal/allowed_experiments.json`. For other libraries and |
| # packages, passing the experiment flag is still required to turn on the |
| # experiment. |
| # |
| # Shipped: |
| # When an experiment is shipped, then the 'enabledIn' field is added |
| # indicating which version of the SDK contains this new language feature. |
| # At this point, specifying the flag on the command line has no effect because |
| # the experiment is enabled by default and cannot be disabled. |
| # |
| # Retired or Rejected: |
| # At some point, the 'expired' field is added to the experiment indicating |
| # that the flag is to be retired if the experiment has shipped or that the |
| # entire experiment was rejected if the experiment has not shipped. It also |
| # indicates that the corresponding entry is slated for eventual removal |
| # from this file. Users specifying this flag on the command line should receive |
| # a warning that the experiment has been retired or rejected, but the tool |
| # should continue to run. |
| # |
| # In addition, there is also a value called "current-version" |
| # specifying the version of Dart that is currently being developed. |
| # Dart source files that don't specify their own version will be |
| # presumed to be in this version. Experiment flags will not affect |
| # files that specify an earlier version. |
| # |
| # Furthermore, most of the above was designed with language features |
| # (spanning both CFE and Analyzer) in mind, but didn't take into account |
| # features in individual products (e.g. in CFE that has no influence on |
| # Analyzer). As a stepping-stone to allow for this usage as well, a "category" |
| # is also available. If no "category" is specified it's assumed to be the |
| # default 'language' "category" with code generated for both CFE and Analyzer, |
| # while other categories can be tailored more specifically. |
| |
| current-version: '2.15.0' |
| |
| features: |
| variance: |
| help: "Sound variance" |
| |
| alternative-invalidation-strategy: |
| help: "Alternative invalidation strategy for incremental compilation." |
| category: "CFE" |
| |
| value-class: |
| help: "Value class" |
| |
| extension-types: |
| help: "Extension Types" |
| |
| const-functions: |
| help: "Allow more of the Dart language to be executed in const expressions." |
| |
| # Experiment flag only used for testing. |
| test-experiment: |
| help: >- |
| Has no effect. Can be used for testing the --enable-experiment |
| command line functionality. |
| |
| # |
| # Flags below this line are shipped, retired, or rejected, cannot be specified |
| # on the command line, and will eventually be removed. |
| # |
| |
| nonfunction-type-aliases: |
| help: "Type aliases define a <type>, not just a <functionType>" |
| enabledIn: '2.13.0' |
| validation: | |
| typedef S = String; |
| void main() { |
| S s = 'feature enabled'; |
| print(s); |
| } |
| |
| non-nullable: |
| help: "Non Nullable by default" |
| experimentalReleaseVersion: '2.10.0' |
| enabledIn: '2.12.0' |
| validation: | |
| void main() { |
| int? a = null; |
| print('feature enabled'); |
| } |
| |
| extension-methods: |
| help: "Extension Methods" |
| enabledIn: '2.6.0' |
| |
| constant-update-2018: |
| help: "Enhanced constant expressions" |
| enabledIn: '2.0.0' |
| expired: true |
| |
| control-flow-collections: |
| help: "Control Flow Collections" |
| enabledIn: '2.0.0' |
| expired: true |
| |
| generic-metadata: |
| help: >- |
| Allow annotations to accept type arguments; |
| also allow generic function types as type arguments. |
| enabledIn: '2.14.0' |
| |
| set-literals: |
| help: "Set Literals" |
| enabledIn: '2.0.0' |
| expired: true |
| |
| spread-collections: |
| help: "Spread Collections" |
| enabledIn: '2.0.0' |
| expired: true |
| |
| triple-shift: |
| help: "Triple-shift operator" |
| enabledIn: '2.14.0' |
| validation: | |
| class A { |
| operator>>>(int k) => 42; |
| } |
| void main() { |
| if ((A() >>> 1) == 42) print('feature enabled'); |
| } |
| |
| constructor-tearoffs: |
| help: "Allow constructor tear-offs and explicit generic instantiations." |
| enabledIn: '2.15.0' |
| validation: | |
| class A { |
| A() { |
| print('feature enabled'); |
| } |
| } |
| void main() { |
| var c = A.new; |
| c(); |
| } |