Razor Source Generator is throwing and Razor tooling never lights up

[SteveSandersonMS]

Repro:

• Use VS 2022 - 17.0.0 Preview 5.0 [31706.66.main]
• Use .NET SDK 6.0.100-rc.2.21456.8
• Create a new project with Blazor WebAssembly, enabling "ASP.NET Core hosted" option
• Open Client\Pages\Index.razor in editor
• Wait for the tag helpers to light up on the components in the source (i.e. PageTitle and SurveyPrompt being shown as components rather than HTML elements).
  • OTHER BUG: They do not, even after waiting for 2 minutes. (If this is a tooling bug rather than a RSG bug, we need to file a separate issue for that - what do you think @pranavkm @NTaylorMullen?)
• Run the application using Ctrl+F5
• While running, try editing the <h1> in the page to have some other text, and press save.
• Wait for hot reload to be applied
  • OTHER BUG: It is not, and gives the "Edits were made which cannot be compiled" prompt, so click "Stop". I filed a separate issue for this at dotnet watch hot reload not working in default WebAssembly Hosted project template (RC2) #36218 (comment)
• Press ctrl+shift+b to rebuild the solution

Get the following exception:

It's possible that some common underlying issue is causing all these problems, but it's hard to know.

Maybe I need to get some magic combination of VS/SDK versions that work together well, but I don't know how we'd know which ones are right for each other. Please let me know if there is some system for doing that. Having neither hot reload nor Razor tooling working currently means we can't evaluate the end developer experience, which is a strong concern this late in the release cycle!