laravelのバージョンアップデートでのエラー

Question

前提・実現したいこと

laravelでtodoappのようなものを作成しているのですが、バージョンを間違えてダウンロードしてしまったため、バージョンのアップロードに取り組みました。ところが、エラーが発生し、アップデート前まで問題なく使えていた"php artisan serve"など使えなくなってしまいました。解決策を教えていただきたいです。

発生している問題・エラーメッセージ

Loading composer repositories with package information
Updating dependencies
Your requirements could not be resolved to an installable set of packages.

Problem 1
- Conclusion: don't install laravel/framework v7.0.0 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.0.1 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.0.2 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.0.3 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.0.4 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.0.5 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.0.6 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.0.7 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.0.8 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.1.0 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.1.1 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.1.2 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.1.3 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.2.0 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.2.1 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.2.2 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.3.0 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.4.0 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.5.0 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.5.1 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.5.2 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.6.0 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.6.1 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.6.2 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.7.0 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.7.1 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.8.0 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.8.1 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.9.0 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.9.1 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.9.2 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.10.0 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.10.1 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.10.2 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.10.3 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.11.0 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.12.0 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.13.0 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.14.0 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.14.1 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.15.0 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.16.0 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.16.1 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.17.0 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.17.1 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.17.2 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.18.0 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.19.0 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.19.1 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.20.0 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.21.0 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.22.0 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.22.1 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.22.2 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.22.3 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.22.4 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.23.0 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.23.1 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.23.2 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.24.0 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.25.0 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.26.0 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.26.1 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.27.0 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.28.0 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.28.1 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.28.2 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.28.3 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.28.4 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.29.0 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.29.1 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.29.2 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.29.3 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.30.0 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.30.1 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.30.2 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.30.3 (conflict analysis result)
- Conclusion: don't install laravel/framework v7.30.4 (conflict analysis result)
- laravel/ui[v1.2.0, ..., 1.x-dev] require illuminate/support ~5.8|^6.0 -> satisfiable by illuminate/support[v5.8.0, ..., 5.8.x-dev, v6.0.0, ..., 6.x-dev].
- Only one of these can be installed: illuminate/support[v5.4.0, ..., 5.8.x-dev, v6.0.0, ..., 6.x-dev, v7.0.0, ..., 7.x-dev, v8.0.0, ..., 8.x-dev], laravel/framework[v7.0.0, ..., 7.x-dev]. laravel/framework replaces illuminate/support and thus cannot coexist with it.
- Root composer.json requires laravel/framework ^7.0 -> satisfiable by laravel/framework[v7.0.0, ..., 7.x-dev].
- Root composer.json requires laravel/ui ^1.2 -> satisfiable by laravel/ui[v1.2.0, v1.3.0, 1.x-dev].

試したこと

composer require laravel/helpers

上記を試したところ
Your requirements could not be resolved to an installable set of packages.

Problem 1
- laravel/ui[v1.2.0, ..., 1.x-dev] require illuminate/console ~5.8|^6.0 -> found illuminate/console[v5.8.0, ..., 5.8.x-dev, v6.0.0, ..., 6.x-dev] but these were not loaded, likely because it conflicts with another require.
- Root composer.json requires laravel/ui ^1.2 -> satisfiable by laravel/ui[v1.2.0, v1.3.0, 1.x-dev].

Installation failed, reverting ./composer.json and ./composer.lock to their original content.

このようなエラーが出てしまいます。

Comments

[Lulucom]

Laravelプロジェクトを作成されたばかりでしたら、本来使いたいバージョンでLaravelプロジェクトを作成し直すのが手っ取り早い気はするのですが・・・

もう少し詳しい情報を追記していただくと、見た方も状況を理解でき、回答も付きやすくなるのではないでしょうか。少なくとも次のような情報は必要ではないかと思います。
・最初にダウンロードされたバージョン
・どのバージョンにアップデートしたいか
・バージョンのアップロードに取り組まれたそうですが、具体的にはどのような操作をされたのか