Use better implementation of hashCode when available

sum_data_types_generator/lib/common.dart

@@ -2,6 +2,7 @@ import 'package:analyzer/dart/analysis/features.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/type.dart';
 import 'package:meta/meta.dart';
+import 'package:pub_semver/pub_semver.dart';
 import 'package:source_gen/source_gen.dart';
 import 'package:sum_data_types/sum_data_types.dart';
 
@@ -167,11 +168,13 @@ class CodgenConfig {
   final bool genToString;
   final bool genEqHashCode;
   final bool nnbd;
+  final bool hashCodeImpl;
 
   const CodgenConfig({
     bool? toString,
     bool? eqHashCode,
     required this.nnbd,
+    required this.hashCodeImpl,
   })   : genToString = toString ?? true,
         genEqHashCode = eqHashCode ?? true;
 }
@@ -217,6 +220,7 @@ class CommonClassModel<FieldModel> {
         toString: genToString,
         eqHashCode: genEqHashCode,
         nnbd: lib.featureSet.isEnabled(Feature.non_nullable),
+        hashCodeImpl: lib.languageVersion.effective >= Version(2, 14,0),
       );
 
       final mixinName = clazz.name;
@@ -281,19 +285,26 @@ String eqImpl(String className, List<String> fieldNames) {
     }''';
 }
 
-String hashCodeImpl(List<String> fieldNames) {
-  if (fieldNames.isEmpty) {
+String hashCodeImpl(CodgenConfig config, List<String> fieldNames) {
+  if (config.hashCodeImpl) {
+      final updates = fieldNames.map((name) => 'this.$name,').join();
+      return '''@override
+        int get hashCode => Object.hashAll([$updates]);
+      ''';
+  } else {
+    if (fieldNames.isEmpty) {
+      return '''@override
+        int get hashCode => 0;
+      ''';
+    }
+    const result = r'__result$';
+    final updates =
+        fieldNames.map((name) => '$result = 37 * $result + this.$name.hashCode;').join('\n');
     return '''@override
-      int get hashCode => 0;
-    ''';
+      int get hashCode {
+        var $result = 17;
+        $updates
+        return $result;
+      }''';
   }
-  const result = r'__result$';
-  final updates =
-      fieldNames.map((name) => '$result = 37 * $result + this.$name.hashCode;').join('\n');
-  return '''@override
-    int get hashCode {
-      var $result = 17;
-      $updates
-      return $result;
-    }''';
 }

sum_data_types_generator/lib/data_classes.dart

@@ -220,7 +220,7 @@ class DataClassGenerator extends GeneratorForAnnotation<DataClass> {
 
           ${clazz.config.genEqHashCode ? eqImpl(clazz.className, clazz.fieldNames) : ''}
 
-          ${clazz.config.genEqHashCode ? hashCodeImpl(clazz.fieldNames) : ''}
+          ${clazz.config.genEqHashCode ? hashCodeImpl(clazz.config, clazz.fieldNames) : ''}
 
           ${clazz.config.genToString ? toStringMethod : ''}
         }''';

sum_data_types_generator/lib/sum_types.dart

@@ -290,7 +290,7 @@ class SumTypeGenerator extends GeneratorForAnnotation<SumType> {
 
           ${clazz.config.genEqHashCode ? eqImpl(clazz.className, clazz.internalFieldNames) : ''}
 
-          ${clazz.config.genEqHashCode ? hashCodeImpl(clazz.internalFieldNames) : ''}
+          ${clazz.config.genEqHashCode ? hashCodeImpl(clazz.config, clazz.internalFieldNames) : ''}
 
           ${clazz.config.genToString ? toStringMethod : ''}
         }

sum_data_types_generator/pubspec.yaml

@@ -7,12 +7,13 @@ environment:
   sdk: '>=2.12.0 <3.0.0'
 
 dependencies:
-  analyzer: ^1.3.0
-  pedantic: ^1.8.0
+  analyzer: ^2.2.0
   build: ^2.0.0
   meta: ^1.1.7
-  sum_data_types: ^0.1.1
+  pedantic: ^1.8.0
+  pub_semver: ^2.0.0
   source_gen: ^1.0.0
+  sum_data_types: ^0.1.1
 
 dev_dependencies:
-  build_runner: ^1.12.2
+  build_runner: ^2.1.2