When using `freezed 3.2.3` with `Dart 3.10.4` (Flutter 3.38.5 stable), the Dart compiler fails to recognize mixin implementations generated by freezed, resulting in compilation errors for ALL @freezed classes

[jorgexforte]

When using freezed 3.2.3 with Dart 3.10.4 (Flutter 3.38.5 stable), the Dart compiler fails to recognize mixin implementations generated by freezed, resulting in compilation errors for ALL @freezed classes.

freezed_bug_report_20251220_132618.tar.gz

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Error Message

error • Missing concrete implementation of 'getter mixin _$ClassName on Object.propertyName'
       • non_abstract_class_inherits_abstract_member

Key observation: Error says "on Object" instead of "on ClassName", suggesting the mixin is not being applied correctly to the class.

---

📋 Environment

• freezed: 3.2.3
• freezed_annotation: 3.1.0
• build_runner: 2.10.4
• Dart SDK: 3.10.4 (stable) - Flutter 3.38.5
• OS: Linux (Arch Linux, kernel 6.18.2)
• Also tested with:
  • Dart 3.11.0 (Flutter 3.40.0-0.2.pre beta) → Same error
  • Dart 3.6.0 (Flutter 3.27.1 stable) → Works fine with freezed 2.x

---

🔬 Minimal Reproducible Example

I've created a minimal project that reproduces the issue:

Project Structure

freezed_test_minimal/
├── lib/
│   └── test_model.dart
├── pubspec.yaml
└── (generated files)

pubspec.yaml

name: freezed_test_minimal
description: Minimal reproducible example for freezed 3.2.3 + Dart 3.10.4 bug

environment:
  sdk: '>=3.10.0 <4.0.0'
  flutter: '>=3.38.0'

dependencies:
  flutter:
    sdk: flutter
  freezed_annotation: ^3.1.0

dev_dependencies:
  flutter_test:
    sdk: flutter
  freezed: ^3.2.3
  build_runner: ^2.10.4

lib/test_model.dart

import 'package:freezed_annotation/freezed_annotation.dart';

part 'test_model.freezed.dart';

@freezed
class TestModel with _$TestModel {
  const factory TestModel({required String id}) = _TestModel;
}

Steps to Reproduce

# 1. Create project
flutter create freezed_test_minimal
cd freezed_test_minimal

# 2. Add dependencies
flutter pub add freezed_annotation
flutter pub add --dev freezed build_runner

# 3. Create test model (see above)

# 4. Generate code
dart run build_runner build --delete-conflicting-outputs
# ✅ SUCCESS: Built with build_runner/jit in 5s; wrote 1 output.

# 5. Analyze
flutter analyze lib/test_model.dart
# ❌ ERROR: Missing concrete implementation of 'getter mixin _$TestModel on Object.id'

---

🔍 Analysis of Generated Code

The generated test_model.freezed.dart file appears structurally correct:

Mixin definition (line 15-41):

mixin _$TestModel {
  String get id;  // ✅ Getter defined

  @JsonKey(includeFromJson: false, includeToJson: false)
  @pragma('vm:prefer-inline')
  $TestModelCopyWith<TestModel> get copyWith => ...;

  @override
  bool operator ==(Object other) { ... }

  @override
  int get hashCode => Object.hash(runtimeType, id);

  @override
  String toString() => 'TestModel(id: $id)';
}

Concrete class (line 208-237):

class _TestModel implements TestModel {
  const _TestModel({required this.id});

  @override
  final String id;  // ✅ Property implemented

  @override
  @JsonKey(includeFromJson: false, includeToJson: false)
  @pragma('vm:prefer-inline')
  _$TestModelCopyWith<_TestModel> get copyWith => ...;

  // All other methods implemented correctly
}

Source class:

@freezed
class TestModel with _$TestModel {  // Mixin applied
  const factory TestModel({required String id}) = _TestModel;
}

Observation

The generated code follows the exact pattern documented in freezed's README:

1. ✅ Mixin _$TestModel defines getters
2. ✅ Concrete class _TestModel implements all properties
3. ✅ Source class TestModel uses with _$TestModel

But: Dart 3.10.4 compiler does not recognize the mixin implementation.

---

🧪 Additional Testing

Test 1: Large Project (327 errors)

Original issue discovered in a large Flutter project with:

• 20+ @freezed models (69 @freezed classes total)
• Riverpod 3.x state management
• Clean Architecture pattern

Result: All 327 compilation errors related to freezed mixins.

Test 2: Dart Versions

Dart Version	Flutter Version	freezed Version	Result
3.6.0	3.27.1 stable	2.5.7	✅ Works
3.10.4	3.38.5 stable	3.2.3	❌ Fails
3.11.0	3.40.0-0.2.pre beta	3.2.3	❌ Fails

Test 3: Clean Operations

Attempted fixes (all failed):

• flutter clean
• dart run build_runner clean
• rm -rf .dart_tool/build
• Multiple regenerations
• Fresh Flutter SDK installation

Conclusion: Issue is consistent and reproducible across different environments with Dart 3.10+.

---

💡 Expected Behavior

The code should compile without errors, as it does with:

• freezed 2.5.7 + Dart 3.6.0 ✅
• freezed 3.x + Dart 3.6.0 ✅ (presumably)

---

🔧 Current Workaround

Downgrade to freezed 2.x is NOT viable because:

• freezed 2.5.7 requires _macros from SDK that doesn't exist in Dart 3.10.4
• freezed 2.x is incompatible with Dart 3.8+
• Would require downgrading entire dependency tree (Riverpod 3.x, etc.)

Temporary solution:
Replace @freezed classes with manual Dart classes until fix is available.

---

📎 Attachments

I can provide:

1. ✅ Minimal reproducible project (available at /tmp/freezed_test_minimal)
2. ✅ Generated .freezed.dart file for inspection
3. ✅ Full error logs
4. ✅ Large project pubspec.yaml for context

---

🙏 Request

Is this a known issue with Dart 3.10.x?

If so, is there:

1. An ETA for a fix?
2. A recommended workaround?
3. A specific Dart version to use with freezed 3.x?

This is blocking development for projects that require Dart 3.8+ (for dependencies like Riverpod 3.x, very_good_analysis 10.x, etc.).

---

📚 Related Issues

(Search before posting - add links to similar issues if found)

---

Environment Details:

$ flutter --version
Flutter 3.38.5 • channel stable
Framework • revision 1ba1d176de (2 weeks ago)
Engine • revision 49d1d44610
Tools • Dart 3.10.4 • DevTools 2.43.2

$ dart --version
Dart SDK version: 3.10.4 (stable) (Tue Nov 18 11:02:31 2025 -0800) on "linux_x64"

$ flutter pub deps | grep freezed
|-- freezed_annotation 3.1.0
`-- freezed 3.2.3

---

Thank you for maintaining this excellent package!

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---

🔗 Similar Issues

Possible Duplicates

• Freezed 3.2.3: Generated mixin getters compressed to single line causing compilation errors #1318

Related Issues

• Freezed v3 does not generate fromJson/toJson #1191
• Incorrect inheritance generation when base class is located in a separate file #1197
• Failed to precompile build. This is likely caused by a misconfigured builder definition. #1239
• Incorrect inheritance generation when base class is located in a separate file #1196
• Freezed inheritance and JSON #1258
• Build error with generic freezed model in latest version #1249

🔗 Related PRs

#1158 - External factory [merged]
#1174 - Handle extra edge-cases [merged]
#1183 - Update docs for Freezed v3 [merged]
#1229 - Fixes null exception [merged]
#1266 - Use built_test 3.2.1, test fixes. [merged]

👤 Suggested Assignees

• rrousselGit
• bobhu2k
• lume-code
• daniellampl
• Helohi

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💬 Have feedback or questions? Drop into our discord or schedule a call!

[SangWook16074]

This happens because @freezed generates abstract members.
If the class is not marked as abstract or sealed,
the analyzer reports non_abstract_class_inherits_abstract_member.

Add abstract (or sealed) before the class declaration:

@freezed
abstract class TestModel with _$TestModel {
  const factory TestModel({required String id}) = _TestModel;
}

Same root cause as issue #1328.

[AdamTechAcc]

Ugly bug.

[Mikelenjilo]

Follow the migration guide from v2 to v3 (migration guide), you have to use abstract or sealed.

Please close this issue.