"Error CS7069" thrown when Assembly Definition Asset platform is set to Editor only
Unity: Scripting Buildtime
As Designed
6.5.X
6.4.X
6.3.X
6.2.X
6.0.X
Thank you for reporting a bug to Unity.
Unfortunately this isn't something we'd be able to address at this time. It seems that setting the Project Setting in the Editor to .Net Standard 2.1 fixes this issue.
How to reproduce:
1. Open attached project "IN-123923"
2. In Project Panel enter EditorPackage folder and select EditorPackage
3. In the Inspector uncheck "Any Platform", select only Editor then press Apply
4. Observe Console
Expected result: No errors appear in console
Actual result: “error CS7069: Reference to type 'ReadOnlySpan<>' claims it is defined in 'mscorlib', but it could not be found” appears in console