Intellisense reporting error for source generated type, but runs fine

[MisinformedDNA]

The intellisense keeps reporting an error that the source generated type doesn't exist, but the type is found in the assembly and and the error doesn't block the build anyway.

Repro:

1. Clone https://github.com/davidwengier/SourceGeneratorTemplate
2. Open VS2019 16.8.1
3. Run ConsoleApp
4. Note that it runs fine and Foo is listed as a type in the assembly
5. Open Program.cs in ConsoleApp
6. Add var foo = new Foo();

EXPECTED: Type is recognized.

ACTUAL: Get compiler error

The type or namespace name 'Foo' could not be found (are you missing a using directive or an assembly reference?)

7. Run ConsoleApp
8. Note that it runs fine even with the error

[jmarolf]

@chsienki should this be in this repo or moved to roslyn?

[ugumba]

Seconded. Without Intellisense, generated code is almost impossible to consume - especially as it is not even put anywhere on disk (that I could find).

[chsienki]

I'm pretty sure this is another case of dotnet/roslyn#48083

I'll close this as a dupe, but feel free to add onto the referenced bug.