Providing Container a color and decoration produces an unclear error message

Similar to #36161, but that issue was closed with the incorrect error message in place.

Steps to Reproduce

Create a Container with any valid color property.
Add the decoration property to the container.
Give decoration a BoxDecoration with a valid color property.
An exception is caught and an error message is printed.

Expected results:
An error message that clearly defines the issue and optionally provides a way to fix the error.

Actual results:

════════ Exception caught by widgets library ═══════════════════════════════════
The following assertion was thrown building Themes(dirty, dependencies: [_InheritedTheme, _LocalizationsScope-[GlobalKey#50d61]]):
Cannot provide both a color and a decoration
To provide both, use "decoration: BoxDecoration(color: color)".

The error message clearly defines the issue, however the suggested fix reads: To provide both, use "decoration: BoxDecoration(color: color)".
This is an incorrect suggestion because Container has checks to verify it was NOT provided both. The error message should clearly communicate the proper condition--which is passing Container.color OR Container.decoration, not both like the error message is suggesting.

Example:

import 'package:flutter/material.dart';

void main() {
  runApp(new MaterialApp(
    home: new HomePage(),
  ));
}

class HomePage extends StatefulWidget {
  @override
  _HomePageState createState() => new _HomePageState();
}

class _HomePageState extends State<HomePage> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Container(
        width: 50.0,
        height: 50.0,
        color: Colors.blue,
        decoration: BoxDecoration(
          color: Colors.blue,
      ),
    );
  }
}

@JoshMart

Thanks for the report @JoshMart
The Container widget's documentation says:

/// The `color` and `decoration` arguments cannot both be supplied, since
  /// it would potentially result in the decoration drawing over the background
  /// color. To supply a decoration with a color, use `decoration:
  /// BoxDecoration(color: color)`.

Indicating you should not do below:

color: Colors.blue,
decoration: BoxDecoration(
color: Colors.blue,
),

And that's what the error message in console also indicates:

Cannot provide both a color and a decoration
To provide both, use "decoration: BoxDecoration(color: color)".

Which I think is well explained and this assertion also helps to indicate what changes you need to make in your code implementation.

Let us know if this helps to address the issue you raised.

Thanks for the response. I would agree that within the context of the Container documentation this error messages begins to make more sense. However the user does not see the additional comment block you provided unless they start digging through the source code. From the perspective of the user:

A user provides both a color and decoration
They receive an error message saying says Cannot provide both a color and a decoration To provide both, use "decoration: BoxDecoration(color: color)"..
The user wants to provide both, so they follow the error message by providing both and using the decoration formatted to how the error message printed it out.
The user gets the same error message and the loop continues until they break it by finally digging in the the source code or searching for an answer elsewhere.

The error message is vague because it contradicts itself by saying Cannot provide both... To provide both. In fact, you had to go into the source code and provide documentation from Container in order to put the error message in context and provide more clarity. That is another smell the error message isn't clear enough to stand on its own--the user shouldn't have to dig through source code in order to understand an error message.

The error message also makes it sound like you can still provide both--which the second part of the error message says you can do-- by using the exact decoration given in the error message. It would be more clear if To provide both was dropped from the second part of the error message and replaced with entirely different wording. Maybe something like To set a color with a decoration, ....

Thanks for the feedback. I am keeping this issue open for team's thoughts on current error message displayed and if there's any scope to improve per OP.

Improve Container color/decoration error message clarity

I can confirm this assertion is very confusing for newcomers. As a beginner, when I first encountered this "To provide both..." message, I was thoroughly confused and wasted significant time trying to follow the contradictory instruction. This is a severe hurdle for new users.

It's nearly the end of 2025, and this issue appears to be left in the dust of history.

Fix misleading error message for color/decoration conflict

Improve Container color/decoration error message clarity (#178823)

Fix misleading error message for color/decoration conflict

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.

Fix misleading error message for color/decoration conflict

Fix misleading error message for color/decoration conflict (relands #…

Fix misleading error message for color/decoration conflict (relands f…

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Providing Container a color and decoration produces an unclear error message #119484

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Providing Container a color and decoration produces an unclear error message #119484

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darshankawar commented on Jan 30, 2023

JoshMart commented on Jan 30, 2023

darshankawar commented on Jan 31, 2023

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baoyachi commented on Dec 4, 2025

github-actions commented on Jan 19, 2026

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