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// 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.
import 'package:analyzer/src/dart/analysis/experiments.dart';
import 'package:pub_semver/pub_semver.dart';
/// Information about a single language feature whose presence or absence
/// depends on the supported Dart SDK version, and possibly on the presence of
/// experimental flags.
abstract class Feature {
/// Feature information for the 2018 constant update.
static final constant_update_2018 = ExperimentalFeatures.constant_update_2018;
/// Feature information for non-nullability by default.
static final non_nullable = ExperimentalFeatures.non_nullable;
/// Feature information for constructor tear-offs.
static final constructor_tearoffs = ExperimentalFeatures.constructor_tearoffs;
/// Feature information for control flow collections.
static final control_flow_collections =
/// Feature information for enhanced enums.
static final enhanced_enums = ExperimentalFeatures.enhanced_enums;
/// Feature information for extension methods.
static final extension_methods = ExperimentalFeatures.extension_methods;
/// Feature information for extension types.
static final extension_types = ExperimentalFeatures.extension_types;
/// Feature information for generic metadata.
static final generic_metadata = ExperimentalFeatures.generic_metadata;
/// Feature information for inference-update-1.
static final inference_update_1 = ExperimentalFeatures.inference_update_1;
/// Feature information for macros.
static final macros = ExperimentalFeatures.macros;
/// Feature information for records.
static final records = ExperimentalFeatures.records;
/// Feature information for spread collections.
static final spread_collections = ExperimentalFeatures.spread_collections;
/// Feature information for set literals.
static final set_literals = ExperimentalFeatures.set_literals;
/// Feature information for super parameters.
static final super_parameters = ExperimentalFeatures.super_parameters;
/// Feature information for the triple-shift operator.
static final triple_shift = ExperimentalFeatures.triple_shift;
/// Feature information for named arguments anywhere.
static final named_arguments_anywhere =
/// Feature information for non-function type aliases.
static final nonfunction_type_aliases =
/// Feature information for variance.
static final variance = ExperimentalFeatures.variance;
/// If the feature may be enabled or disabled on the command line, the
/// experimental flag that may be used to enable it. Otherwise `null`.
/// Should be `null` if [status] is `current` or `abandoned`.
String? get experimentalFlag;
/// If [status] is not `future`, the first language version in which this
/// feature was enabled by default. Otherwise `null`.
Version? get releaseVersion;
/// The status of the feature.
FeatureStatus get status;
/// An unordered collection of [Feature] objects.
abstract class FeatureSet {
/// Computes the set of features implied by the given set of experimental
/// enable flags.
factory FeatureSet.fromEnableFlags2({
required Version sdkLanguageVersion,
required List<String> flags,
}) = ExperimentStatus.fromStrings2;
/// Computes the set of features for the latest language version known
/// to the analyzer, without any experiments. Use it only if you really
/// don't care which language version you want to use, and sure that the
/// code that you process is valid for the latest language version.
/// Otherwise, it is recommended to use [FeatureSet.fromEnableFlags2].
factory FeatureSet.latestLanguageVersion() =
/// Queries whether the given [feature] is contained in this feature set.
bool isEnabled(Feature feature);
/// Computes a subset of this FeatureSet by removing any features that are
/// not available in the given language version.
FeatureSet restrictToVersion(Version version);
/// Information about the status of a language feature.
enum FeatureStatus {
/// The language feature has not yet shipped. It may not be used unless an
/// experimental flag is used to enable it.
/// The language feature has not yet shipped, but we are testing the effect of
/// enabling it by default. It may be used in any library with an appropriate
/// version constraint, unless an experimental flag is used to disable it.
/// The language feature has been shipped. It may be used in any library with
/// an appropriate version constraint.
/// The language feature is no longer planned. It may not be used.