Add "enhanced-enums" experiment flag

Part of https://github.com/dart-lang/sdk/issues/47453.

Change-Id: I6d1fdc4bc170354985a9d216b13ad8f153717adf
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/216662
Reviewed-by: Johnni Winther <johnniwinther@google.com>
Commit-Queue: Chloe Stefantsova <dmitryas@google.com>

pkg/analyzer/lib/src/dart/analysis/experiments.g.dart

@@ -17,6 +17,7 @@ final _knownFeatures = <String, ExperimentalFeature>{
   EnableString.constructor_tearoffs: ExperimentalFeatures.constructor_tearoffs,
   EnableString.control_flow_collections:
       ExperimentalFeatures.control_flow_collections,
+  EnableString.enhanced_enums: ExperimentalFeatures.enhanced_enums,
   EnableString.extension_methods: ExperimentalFeatures.extension_methods,
   EnableString.extension_types: ExperimentalFeatures.extension_types,
   EnableString.generic_metadata: ExperimentalFeatures.generic_metadata,
@@ -46,6 +47,9 @@ class EnableString {
   /// String to enable the experiment "control-flow-collections"
   static const String control_flow_collections = 'control-flow-collections';
 
+  /// String to enable the experiment "enhanced-enums"
+  static const String enhanced_enums = 'enhanced-enums';
+
   /// String to enable the experiment "extension-methods"
   static const String extension_methods = 'extension-methods';
 
@@ -123,8 +127,18 @@ class ExperimentalFeatures {
     releaseVersion: Version.parse('2.0.0'),
   );
 
-  static final extension_methods = ExperimentalFeature(
+  static final enhanced_enums = ExperimentalFeature(
     index: 4,
+    enableString: EnableString.enhanced_enums,
+    isEnabledByDefault: IsEnabledByDefault.enhanced_enums,
+    isExpired: IsExpired.enhanced_enums,
+    documentation: 'Enhanced Enums',
+    experimentalReleaseVersion: null,
+    releaseVersion: null,
+  );
+
+  static final extension_methods = ExperimentalFeature(
+    index: 5,
     enableString: EnableString.extension_methods,
     isEnabledByDefault: IsEnabledByDefault.extension_methods,
     isExpired: IsExpired.extension_methods,
@@ -134,7 +148,7 @@ class ExperimentalFeatures {
   );
 
   static final extension_types = ExperimentalFeature(
-    index: 5,
+    index: 6,
     enableString: EnableString.extension_types,
     isEnabledByDefault: IsEnabledByDefault.extension_types,
     isExpired: IsExpired.extension_types,
@@ -144,7 +158,7 @@ class ExperimentalFeatures {
   );
 
   static final generic_metadata = ExperimentalFeature(
-    index: 6,
+    index: 7,
     enableString: EnableString.generic_metadata,
     isEnabledByDefault: IsEnabledByDefault.generic_metadata,
     isExpired: IsExpired.generic_metadata,
@@ -155,7 +169,7 @@ class ExperimentalFeatures {
   );
 
   static final non_nullable = ExperimentalFeature(
-    index: 7,
+    index: 8,
     enableString: EnableString.non_nullable,
     isEnabledByDefault: IsEnabledByDefault.non_nullable,
     isExpired: IsExpired.non_nullable,
@@ -165,7 +179,7 @@ class ExperimentalFeatures {
   );
 
   static final nonfunction_type_aliases = ExperimentalFeature(
-    index: 8,
+    index: 9,
     enableString: EnableString.nonfunction_type_aliases,
     isEnabledByDefault: IsEnabledByDefault.nonfunction_type_aliases,
     isExpired: IsExpired.nonfunction_type_aliases,
@@ -175,7 +189,7 @@ class ExperimentalFeatures {
   );
 
   static final set_literals = ExperimentalFeature(
-    index: 9,
+    index: 10,
     enableString: EnableString.set_literals,
     isEnabledByDefault: IsEnabledByDefault.set_literals,
     isExpired: IsExpired.set_literals,
@@ -185,7 +199,7 @@ class ExperimentalFeatures {
   );
 
   static final spread_collections = ExperimentalFeature(
-    index: 10,
+    index: 11,
     enableString: EnableString.spread_collections,
     isEnabledByDefault: IsEnabledByDefault.spread_collections,
     isExpired: IsExpired.spread_collections,
@@ -195,7 +209,7 @@ class ExperimentalFeatures {
   );
 
   static final test_experiment = ExperimentalFeature(
-    index: 11,
+    index: 12,
     enableString: EnableString.test_experiment,
     isEnabledByDefault: IsEnabledByDefault.test_experiment,
     isExpired: IsExpired.test_experiment,
@@ -206,7 +220,7 @@ class ExperimentalFeatures {
   );
 
   static final triple_shift = ExperimentalFeature(
-    index: 12,
+    index: 13,
     enableString: EnableString.triple_shift,
     isEnabledByDefault: IsEnabledByDefault.triple_shift,
     isExpired: IsExpired.triple_shift,
@@ -216,7 +230,7 @@ class ExperimentalFeatures {
   );
 
   static final value_class = ExperimentalFeature(
-    index: 13,
+    index: 14,
     enableString: EnableString.value_class,
     isEnabledByDefault: IsEnabledByDefault.value_class,
     isExpired: IsExpired.value_class,
@@ -226,7 +240,7 @@ class ExperimentalFeatures {
   );
 
   static final variance = ExperimentalFeature(
-    index: 14,
+    index: 15,
     enableString: EnableString.variance,
     isEnabledByDefault: IsEnabledByDefault.variance,
     isExpired: IsExpired.variance,
@@ -251,6 +265,9 @@ class IsEnabledByDefault {
   /// Default state of the experiment "control-flow-collections"
   static const bool control_flow_collections = true;
 
+  /// Default state of the experiment "enhanced-enums"
+  static const bool enhanced_enums = false;
+
   /// Default state of the experiment "extension-methods"
   static const bool extension_methods = true;
 
@@ -301,6 +318,9 @@ class IsExpired {
   /// Expiration status of the experiment "control-flow-collections"
   static const bool control_flow_collections = true;
 
+  /// Expiration status of the experiment "enhanced-enums"
+  static const bool enhanced_enums = false;
+
   /// Expiration status of the experiment "extension-methods"
   static const bool extension_methods = false;
 
@@ -351,6 +371,9 @@ mixin _CurrentState {
   bool get control_flow_collections =>
       isEnabled(ExperimentalFeatures.control_flow_collections);
 
+  /// Current state for the flag "enhanced-enums"
+  bool get enhanced_enums => isEnabled(ExperimentalFeatures.enhanced_enums);
+
   /// Current state for the flag "extension-methods"
   bool get extension_methods =>
       isEnabled(ExperimentalFeatures.extension_methods);

pkg/front_end/lib/src/api_prototype/experimental_flags_generated.dart

@@ -15,6 +15,7 @@ enum ExperimentalFlag {
   constantUpdate2018,
   constructorTearoffs,
   controlFlowCollections,
+  enhancedEnums,
   extensionMethods,
   extensionTypes,
   genericMetadata,
@@ -34,6 +35,7 @@ const Version enableConstFunctionsVersion = const Version(2, 15);
 const Version enableConstantUpdate2018Version = const Version(2, 0);
 const Version enableConstructorTearoffsVersion = const Version(2, 15);
 const Version enableControlFlowCollectionsVersion = const Version(2, 0);
+const Version enableEnhancedEnumsVersion = const Version(2, 15);
 const Version enableExtensionMethodsVersion = const Version(2, 6);
 const Version enableExtensionTypesVersion = const Version(2, 15);
 const Version enableGenericMetadataVersion = const Version(2, 14);
@@ -58,6 +60,8 @@ ExperimentalFlag? parseExperimentalFlag(String flag) {
       return ExperimentalFlag.constructorTearoffs;
     case "control-flow-collections":
       return ExperimentalFlag.controlFlowCollections;
+    case "enhanced-enums":
+      return ExperimentalFlag.enhancedEnums;
     case "extension-methods":
       return ExperimentalFlag.extensionMethods;
     case "extension-types":
@@ -90,6 +94,7 @@ const Map<ExperimentalFlag, bool> defaultExperimentalFlags = {
   ExperimentalFlag.constantUpdate2018: true,
   ExperimentalFlag.constructorTearoffs: true,
   ExperimentalFlag.controlFlowCollections: true,
+  ExperimentalFlag.enhancedEnums: false,
   ExperimentalFlag.extensionMethods: true,
   ExperimentalFlag.extensionTypes: false,
   ExperimentalFlag.genericMetadata: true,
@@ -109,6 +114,7 @@ const Map<ExperimentalFlag, bool> expiredExperimentalFlags = {
   ExperimentalFlag.constantUpdate2018: true,
   ExperimentalFlag.constructorTearoffs: false,
   ExperimentalFlag.controlFlowCollections: true,
+  ExperimentalFlag.enhancedEnums: false,
   ExperimentalFlag.extensionMethods: false,
   ExperimentalFlag.extensionTypes: false,
   ExperimentalFlag.genericMetadata: false,
@@ -128,6 +134,7 @@ const Map<ExperimentalFlag, Version> experimentEnabledVersion = {
   ExperimentalFlag.constantUpdate2018: const Version(2, 0),
   ExperimentalFlag.constructorTearoffs: const Version(2, 15),
   ExperimentalFlag.controlFlowCollections: const Version(2, 0),
+  ExperimentalFlag.enhancedEnums: const Version(2, 15),
   ExperimentalFlag.extensionMethods: const Version(2, 6),
   ExperimentalFlag.extensionTypes: const Version(2, 15),
   ExperimentalFlag.genericMetadata: const Version(2, 14),
@@ -147,6 +154,7 @@ const Map<ExperimentalFlag, Version> experimentReleasedVersion = {
   ExperimentalFlag.constantUpdate2018: const Version(2, 0),
   ExperimentalFlag.constructorTearoffs: const Version(2, 15),
   ExperimentalFlag.controlFlowCollections: const Version(2, 0),
+  ExperimentalFlag.enhancedEnums: const Version(2, 15),
   ExperimentalFlag.extensionMethods: const Version(2, 6),
   ExperimentalFlag.extensionTypes: const Version(2, 15),
   ExperimentalFlag.genericMetadata: const Version(2, 14),

tools/experimental_features.yaml

@@ -122,6 +122,9 @@ features:
   const-functions:
     help: "Allow more of the Dart language to be executed in const expressions."
 
+  enhanced-enums:
+    help: "Enhanced Enums"
+
 # Experiment flag only used for testing.
   test-experiment:
     help: >-