'package:flutter/src/rendering/stack.dart': Failed assertion: line 664 pos 12: 'size.isFinite': is not true.

Steps to reproduce

Run the code sample.

Expected results

Probably an error message, but one that actually has detail.

Actual results

I get an assertion that tells me to file a bug.

Code sample

import 'package:flutter/material.dart';

void main() {
  runApp(
    Directionality(
      textDirection: TextDirection.ltr,
      child: Column(
        children: [
          Stack(children: [Positioned(top:0,child: SizedBox())]),
        ],
      ),
    ),
  );
}

Screenshots or Video

No response

Logs

log.txt

Flutter Doctor output

Doctor output

[✓] Flutter (Channel main, 3.33.0-1.0.pre-1039, on macOS 14.6.1 23G93 darwin-arm64, locale en-US) [1,230ms]
    • Flutter version 3.33.0-1.0.pre-1039 on channel main at /Users/user/dev/flutter
    • Upstream repository https://github.com/flutter/flutter.git
    • Framework revision 70cdc0c933 (2 hours ago), 2025-07-21 12:09:22 -0400
    • Engine revision 70cdc0c933
    • Dart version 3.10.0 (build 3.10.0-15.0.dev)
    • DevTools version 2.48.0
    • Feature flags: enable-web, enable-linux-desktop, enable-macos-desktop, enable-windows-desktop, enable-android, enable-ios, cli-animations, enable-native-assets

[✗] Android toolchain - develop for Android devices [116ms]
    ✗ Unable to locate Android SDK.
      Install Android Studio from: https://developer.android.com/studio/index.html
      On first launch it will assist you in installing the Android SDK components.
      (or visit https://flutter.dev/to/macos-android-setup for detailed instructions).
      If the Android SDK has been installed to a custom location, please use
      `flutter config --android-sdk` to update to that location.


[!] Xcode - develop for iOS and macOS (Xcode 16.2) [1,044ms]
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • Build 16C5032a
    ✗ Unable to get list of installed Simulator runtimes.
    • CocoaPods version 1.16.2

[✓] Chrome - develop for the web [7ms]
    • Chrome at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome

[!] Android Studio (not installed) [6ms]
    • Android Studio not found; download from https://developer.android.com/studio/index.html
      (or visit https://flutter.dev/to/macos-android-setup for detailed instructions).

[✓] VS Code (version 1.101.2) [6ms]
    • VS Code at /Applications/Visual Studio Code.app/Contents
    • Flutter extension version 3.114.0

[✓] Connected device (2 available) [5.7s]
    • macOS (desktop) • macos  • darwin-arm64   • macOS 14.6.1 23G93 darwin-arm64
    • Chrome (web)    • chrome • web-javascript • Google Chrome 138.0.7204.158

[✓] Network resources [499ms]
    • All expected network resources are available.

! Doctor found issues in 3 categories.

@treeplate

hi @treeplate, thanks for the report. are you suggesting an improvement to the message?

yes

Positioned requires its Stack parent to have bounded constraints, which Column doesn't provide by default. So this is an implementation error, labelling it as a proposal to improve the error message.

Logs

════════ Exception caught by rendering library ═════════════════════════════════
The following assertion was thrown during performLayout():
'package:flutter/src/rendering/stack.dart': Failed assertion: line 663 pos 12: 'size.isFinite': is not true.

Either the assertion indicates an error in the framework itself, or we should provide substantially more information in this error message to help you determine and fix the underlying cause.
In either case, please report this assertion by filing a bug on GitHub:
  https://github.com/flutter/flutter/issues/new?template=02_bug.yml

The relevant error-causing widget was:
    Stack Stack:file:///Users/tirthpatel/j23/lib/main.dart:9:11

When the exception was thrown, this was the stack:
#2      RenderStack._computeSize (package:flutter/src/rendering/stack.dart:663:12)
stack.dart:663
#3      RenderStack.performLayout (package:flutter/src/rendering/stack.dart:672:12)
stack.dart:672
#4      RenderObject.layout (package:flutter/src/rendering/object.dart:2775:7)
object.dart:2775
#5      ChildLayoutHelper.layoutChild (package:flutter/src/rendering/layout_helper.dart:62:11)
layout_helper.dart:62
#6      RenderFlex._computeSizes (package:flutter/src/rendering/flex.dart:1161:28)
flex.dart:1161
#7      RenderFlex.performLayout (package:flutter/src/rendering/flex.dart:1257:32)
flex.dart:1257
#8      RenderObject.layout (package:flutter/src/rendering/object.dart:2775:7)
object.dart:2775
#9      RenderView.performLayout (package:flutter/src/rendering/view.dart:294:12)
view.dart:294
#10     RenderObject._layoutWithoutResize (package:flutter/src/rendering/object.dart:2623:7)
object.dart:2623
#11     PipelineOwner.flushLayout (package:flutter/src/rendering/object.dart:1170:18)
object.dart:1170
#12     PipelineOwner.flushLayout (package:flutter/src/rendering/object.dart:1183:15)
object.dart:1183
#13     RendererBinding.drawFrame (package:flutter/src/rendering/binding.dart:629:23)
binding.dart:629
#14     WidgetsBinding.drawFrame (package:flutter/src/widgets/binding.dart:1261:13)
binding.dart:1261
#15     RendererBinding._handlePersistentFrameCallback (package:flutter/src/rendering/binding.dart:495:5)
binding.dart:495
#16     SchedulerBinding._invokeFrameCallback (package:flutter/src/scheduler/binding.dart:1434:15)
binding.dart:1434
#17     SchedulerBinding.handleDrawFrame (package:flutter/src/scheduler/binding.dart:1347:9)
binding.dart:1347
#18     SchedulerBinding.scheduleWarmUpFrame.<anonymous closure> (package:flutter/src/scheduler/binding.dart:1057:9)
binding.dart:1057
#19     PlatformDispatcher.scheduleWarmUpFrame.<anonymous closure> (dart:ui/platform_dispatcher.dart:886:16)
platform_dispatcher.dart:886
#23     _RawReceivePort._handleMessage (dart:isolate-patch/isolate_patch.dart:193:12)
isolate_patch.dart:193
(elided 5 frames from class _AssertionError, class _Timer, and dart:async-patch)

The following RenderObject was being processed when the exception was fired: RenderStack#f7f91 relayoutBoundary=up1 NEEDS-LAYOUT NEEDS-PAINT NEEDS-COMPOSITING-BITS-UPDATE
    parentData: offset=Offset(0.0, 0.0); flex=null; fit=null (can use size)
    constraints: BoxConstraints(0.0<=w<=411.4, 0.0<=h<=Infinity)
    size: MISSING
    alignment: AlignmentDirectional.topStart
    textDirection: ltr
    fit: loose
    child 1: RenderConstrainedBox#0e1b8 NEEDS-LAYOUT NEEDS-PAINT
        parentData: top=0.0; offset=Offset(0.0, 0.0)
        constraints: MISSING
        size: MISSING
        additionalConstraints: BoxConstraints(unconstrained)
RenderObject: RenderStack#f7f91 relayoutBoundary=up1 NEEDS-LAYOUT NEEDS-PAINT NEEDS-COMPOSITING-BITS-UPDATE
    parentData: offset=Offset(0.0, 0.0); flex=null; fit=null (can use size)
    constraints: BoxConstraints(0.0<=w<=411.4, 0.0<=h<=Infinity)
    size: MISSING
    alignment: AlignmentDirectional.topStart
    textDirection: ltr
    fit: loose
    child 1: RenderConstrainedBox#0e1b8 NEEDS-LAYOUT NEEDS-PAINT
        parentData: top=0.0; offset=Offset(0.0, 0.0)
        constraints: MISSING
        size: MISSING
        additionalConstraints: BoxConstraints(unconstrained)
════════════════════════════════════════════════════════════════════════════════

════════ Exception caught by rendering library ═════════════════════════════════
RenderBox was not laid out: RenderStack#f7f91 relayoutBoundary=up1 NEEDS-PAINT NEEDS-COMPOSITING-BITS-UPDATE
'package:flutter/src/rendering/box.dart':
Failed assertion: line 2251 pos 12: 'hasSize'
The relevant error-causing widget was:
    Column Column:file:///Users/tirthpatel/j23/lib/main.dart:7:14
════════════════════════════════════════════════════════════════════════════════

#78796 (comment)

Hi! I’d love to contribute to this issue.
I plan to improve the assertion error message in RenderStack to clearly explain that the Stack needs bounded constraints (like wrapping it in a SizedBox or Expanded).
Please let me know if I can be assigned or if there’s any guidance. Thanks!

feel free to pick up, it's all yours. thanks for contributing.

@tirth-patel-nc

Hey @tirth-patel-nc ! I’ve updated the assertion to display a clearer error message explaining that Stack needs bounded constraints, with suggestions like using SizedBox, Expanded, or ConstrainedBox.

Could you please take a quick look and let me know if the message looks good?
If it's fine, I’ll go ahead and raise the PR.

Thanks again!

Improve Stack widget error message for bounded constraints (#173352)

Improve Stack widget error message for bounded constraints (flutter#1…

This thread has been automatically locked since there has not been any recent activity after it was closed. If you are still experiencing a similar issue, please open a new bug, including the output of flutter doctor -v and a minimal reproduction of the issue.

Improve Stack widget error message for bounded constraints (flutter#1…

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'package:flutter/src/rendering/stack.dart': Failed assertion: line 664 pos 12: 'size.isFinite': is not true. #172481

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'package:flutter/src/rendering/stack.dart': Failed assertion: line 664 pos 12: 'size.isFinite': is not true. #172481

Description

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Logs

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tirth-patel-nc commented on Jul 22, 2025

treeplate commented on Jul 22, 2025

tirth-patel-nc commented on Jul 23, 2025

Rushikeshbhavsar20 commented on Aug 6, 2025

tirth-patel-nc commented on Aug 6, 2025

Rushikeshbhavsar20 commented on Aug 6, 2025

github-actions commented on Sep 4, 2025

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