Remove unnecessary value key hack in `key.dart` by AbdeMohlbi · Pull Request #189291 · flutter/flutter

AbdeMohlbi · 2026-07-10T21:40:49Z

while reading dart-lang/language#4725, i remembered #178219, the goal of #178219 was to remove the need for an additional class to get the type literal, but thanks to the unhealthy amount of reflection that i have been doing lately (i blame zig) i realized that we can now achieve this directly by checking for type equality, ie:

if (runtimeType == ValueKey<T>) {

for anyone wondering what is this about, here is a little example:

void main(List<String> arguments) {
  typeLitterals();
  anotherTypeLitteralsEaxmple();
}

void typeLitterals() {
  final int x = switch (int) {
    const (int) => 1,
    const (String) => 2,
    _ => 3,
  };
  print(x);
}

void anotherTypeLitteralsEaxmple() {
  const x = (int == int);
  print(x);
}

this prints

1
true

on the other hand :

flutter/packages/flutter/lib/src/foundation/key.dart

Lines 155 to 163 in 07f5016

    
             @override 
        
             String toString() { 
        
               final valueString = T == String ? "<'$value'>" : '<$value>'; 
        
               if (runtimeType == _TypeOf<ValueKey<T>>) { 
        
                 return '[$valueString]'; 
        
               } 
        
               return '[$T $valueString]'; 
        
             } 
        
           }

the reason we have the

   // an instance of ValueKey<T> will hit this branch
if (runtimeType == ValueKey<T>) {
      return '[$valueString]';
    }
   // any classes that extend ValueKey and do not override `toString()` will hit this branch
    return '[$T $valueString]';

if all of this is still confusing check the following test (which passes on HEAD and this branch):

import 'package:flutter/material.dart';
import 'package:flutter_test/flutter_test.dart';

void main() {
  group('ValueKey toString behavior', () {
    test('contains only one value (Standard ValueKey)', () {
      const ValueKey<String> string = ValueKey('string');
      expect(string.toString(), "[<'string'>]");

      const ValueKey<int> c = ValueKey(2);
      expect(c.toString(), "[<2>]");
    });

    test('Subclass without override falls back to type-prefixed format', () {
      const badKey = BadCustomKey<String>('string');
      expect(badKey.toString(), "[String <'string'>]");
    });

    test('Subclass with override uses custom format', () {
      const goodKey = GoodCustomKey<String>('string');
      expect(goodKey.toString(), "[GoodCustomKey <string>]");
    });
  });
}

// missing toString implementation
class BadCustomKey<T> extends ValueKey<T> {
  const BadCustomKey(super.value);
}

class GoodCustomKey<T> extends ValueKey<T> {
  const GoodCustomKey(super.value);

  @override
  String toString() => '[GoodCustomKey <$value>]';
}

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gemini-code-assist

Code Review

This pull request simplifies the toString method in the ValueKey class by directly comparing runtimeType to ValueKey<T> and removing the unused _TypeOf typedef. There are no review comments, and I have no additional feedback to provide.

AbdeMohlbi · 2026-07-13T21:11:58Z

Code Review

This pull request simplifies the toString method in the ValueKey class by directly comparing runtimeType to ValueKey<T> and removing the unused _TypeOf typedef. There are no review comments, and I have no additional feedback to provide.

justinmc

LGTM 👍 . Thanks for following up on this a year later!

flutter-dashboard · 2026-07-15T21:28:10Z

It looks like this pull request may not have tests. Please make sure to add tests or get an explicit test exemption before merging.

If you are not sure if you need tests, consider this rule of thumb: the purpose of a test is to make sure someone doesn't accidentally revert the fix. Ask yourself, is there anything in your PR that you feel it is important we not accidentally revert back to how it was before your fix?

Reviewers: Read the Tree Hygiene page and make sure this patch meets those guidelines before LGTMing. If you believe this PR qualifies for a test exemption, contact "@test-exemption-reviewer" in the #hackers channel in Discord (don't just cc them here, they won't see it!). The test exemption team is a small volunteer group, so all reviewers should feel empowered to ask for tests, without delegating that responsibility entirely to the test exemption group.

stuartmorgan-g · 2026-07-16T14:12:58Z

test-exempt: code refactor with no semantic change

Roll Flutter from fc1ad955f164 to 8005793c3562 (40 revisions) flutter/flutter@fc1ad95...8005793 2026-07-18 [email protected] Remove `LineContents ` experimental AA line shader that is no longer used (flutter/flutter#189619) 2026-07-18 [email protected] Roll Skia from 9468e96cc40f to ba90f98535de (8 revisions) (flutter/flutter#189680) 2026-07-17 [email protected] Roll Dart SDK from 33e4b71e984b to 666e1e2133b7 (2 revisions) (flutter/flutter#189673) 2026-07-17 [email protected] [iOS] Fix potential use-after-free in a11y bridge channel handler (flutter/flutter#189637) 2026-07-17 [email protected] Migrate dev/tools skill validation to new dart_skills_lint API (flutter/flutter#189626) 2026-07-17 [email protected] Add validation for required fields during xcodebuild (flutter/flutter#187772) 2026-07-17 [email protected] Upgrade android_hardware_smoke_test CI to run instrumented tests (flutter/flutter#189390) 2026-07-17 [email protected] Roll Dart SDK from 0867cb1897b5 to 33e4b71e984b (1 revision) (flutter/flutter#189661) 2026-07-17 [email protected] Roll Skia from 702c3e790232 to 9468e96cc40f (1 revision) (flutter/flutter#189660) 2026-07-17 [email protected] Roll Packages from 9f95026 to 4fdc766 (11 revisions) (flutter/flutter#189659) 2026-07-17 [email protected] Roll Skia from 2e4a3ae035cd to 702c3e790232 (1 revision) (flutter/flutter#189655) 2026-07-17 [email protected] [macOS] Add FlutterPluginRegistrar.valuePublished(byPlugin:) just like iOS (flutter/flutter#189614) 2026-07-17 [email protected] Roll Dart SDK from c69d138c9646 to 0867cb1897b5 (2 revisions) (flutter/flutter#189649) 2026-07-17 [email protected] Roll Skia from 4f5aca109c87 to 2e4a3ae035cd (3 revisions) (flutter/flutter#189646) 2026-07-17 [email protected] [iOS] Fix missing nil checks and improve SemanticsObject bridge API (flutter/flutter#189630) 2026-07-17 [email protected] Roll Skia from 37c5e6b26aee to 4f5aca109c87 (19 revisions) (flutter/flutter#189638) 2026-07-17 [email protected] Roll Fuchsia Linux SDK from lLFbh5kFWbUGgC9Ek... to NL8xtzr8cxr5E8r8E... (flutter/flutter#189632) 2026-07-17 [email protected] Add blendMode parameter to RawImage and RenderImage (flutter/flutter#185938) 2026-07-17 [email protected] [web] Cache WASM network requests in flutter test (flutter/flutter#189623) 2026-07-17 [email protected] android_hardware_smoke_tests: Apply semantic line breaks to readme (flutter/flutter#189613) 2026-07-16 [email protected] ci(github-actions): resolve zizmor github-env findings in composite flutter actions (flutter/flutter#189602) 2026-07-16 [email protected] Remove obsolete packages analysis flag (flutter/flutter#189525) 2026-07-16 [email protected] Roll Dart SDK from e24870ff15bc to c69d138c9646 (2 revisions) (flutter/flutter#189597) 2026-07-16 [email protected] [fuchsia][iwyu] Remove transitive include of fuchsia.input.report. (flutter/flutter#188891) 2026-07-16 [email protected] Remove unnecessary value key hack in `key.dart` (flutter/flutter#189291) 2026-07-16 [email protected] Roll Dart SDK from 81306a2ed317 to e24870ff15bc (1 revision) (flutter/flutter#189569) 2026-07-16 [email protected] [Impeller] Fix atlas growth test (flutter/flutter#189533) 2026-07-16 [email protected] Roll Dart SDK from d402ff7c9c84 to 81306a2ed317 (4 revisions) (flutter/flutter#189558) 2026-07-16 [email protected] Move shared darwin plugin tests into own builder (flutter/flutter#189411) 2026-07-16 [email protected] Roll Skia from ab2410bc857c to 37c5e6b26aee (19 revisions) (flutter/flutter#189549) 2026-07-16 [email protected] [ios] Fix //flutter:unittests build for physical devices (flutter/flutter#189543) 2026-07-16 [email protected] Fix lower DragTarget not being recognized in overlapping targets (flutter/flutter#188979) 2026-07-16 [email protected] Relocate cupertino samples that were under widgets/ (flutter/flutter#188876) 2026-07-15 [email protected] [iOS] Migrate DisplayLinkManager to a shared instance (flutter/flutter#189492) 2026-07-15 [email protected] [Impeller] Call glfwTerminate during global test environment teardown if a playground test called glfwInit (flutter/flutter#189523) 2026-07-15 [email protected] Roll pub packages (flutter/flutter#189515) 2026-07-15 [email protected] Roll Packages from ad2eab1 to 9f95026 (8 revisions) (flutter/flutter#189509) 2026-07-15 [email protected] add `@nonVirtual` to `RenderObject.attached`, fix `WidgetTester.hasRunningAnimations` (flutter/flutter#186832) 2026-07-15 [email protected] Roll vulkan-deps to 0582f446e54a (flutter/flutter#188524) 2026-07-15 [email protected] Roll Dart SDK from 0c408ff6dce9 to d402ff7c9c84 (1 revision) (flutter/flutter#189497) If this roll has caused a breakage, revert this CL and stop the roller using the controls here: https://autoroll.skia.org/r/flutter-packages Please CC [email protected],[email protected] on the revert to ensure that a human is aware of the problem. ...

remove uncessary value key hack

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github-actions Bot added the framework flutter/packages/flutter repository. See also f: labels. label Jul 10, 2026

AbdeMohlbi added the CICD Run CI/CD label Jul 10, 2026

AbdeMohlbi added 2 commits July 11, 2026 11:36

Merge branch 'master' into abdemohlbi_remove_unecessary_value_key_hack

a30b58a

Merge branch 'master' into abdemohlbi_remove_unecessary_value_key_hack

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AbdeMohlbi mentioned this pull request Jul 13, 2026

Remove unncessary type getter #189392

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AbdeMohlbi changed the title ~~remove uncessary value key hack~~ Remove unnecessary value key hack in key.dart Jul 13, 2026

AbdeMohlbi marked this pull request as ready for review July 13, 2026 21:08

gemini-code-assist Bot reviewed Jul 13, 2026

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justinmc approved these changes Jul 15, 2026

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Merged via the queue into flutter:master with commit 36b35dd Jul 16, 2026
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AbdeMohlbi mentioned this pull request Jul 23, 2026

Remove unnecessary generic type getter in Factory interface #189600

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Remove unnecessary value key hack in `key.dart` #189291

Remove unnecessary value key hack in `key.dart` #189291
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AbdeMohlbi:abdemohlbi_remove_unecessary_value_key_hack

AbdeMohlbi commented Jul 10, 2026 •

edited

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	@override
	String toString() {
	final valueString = T == String ? "<'$value'>" : '<$value>';
	if (runtimeType == _TypeOf<ValueKey<T>>) {
	return '[$valueString]';
	}
	return '[$T $valueString]';
	}
	}

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AbdeMohlbi commented Jul 10, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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AbdeMohlbi commented Jul 10, 2026 •

edited

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