[Bug]: Namespace ReactiveUI.SourceGenerators doesn't not exists in VS2022 when updated to 2.6.1

Describe the bug 🐞

A bug happened! (this sentence was in template, I better keep it, looks important and totally helpful)

After updating nuget to 2.6.1 from 2.5.1 I start seeing lots of errors eveyrwhere, when opening cs-files containing using ReactiveUI.SourceGenerators; or using [Reactive] attribute on partial properties:

The type or namespace name 'SourceGenerators' does not exist in the namespace 'ReactiveUI' (are you missing an assembly reference?)

The compilation runs without problems. It's only when editing files. Reverting back to 2.5.1 - no problems anymore.

Step to reproduce

1. Update nuget ReactiveUI.SourceGenerators from 2.5.1 to 2.6.1
2. Errors everywhere

Reproduction repository

No response

Expected behavior

This should happen... (oh yeah)

I expect updated version to just work, like previous. Seems not a case, no idea what went wrong exactly.

Screenshots 🖼️

No response

IDE

Visual Studio 2022

Operating system

Microsoft Windows 11 Pro

Version

10.0.26200 Build 26200

Device

PC

ReactiveUI Version

2.6.1

Additional information ℹ️

I will stick with 2.5.1 for now, it's not a problem.

Start by reproducing the editor-only diagnostics in Visual Studio 2022 after updating ReactiveUI.SourceGenerators from 2.5.1 to 2.6.1, using a file with using ReactiveUI.SourceGenerators; and a partial property with [Reactive]. Compare both package versions to isolate the change; done means compilation and editing show no false missing-namespace or attribute errors.