Quick Info for "var" should show the flow state of the initializer

[jasonmalinowski]

With "var" being changed to always infer a nullable type for assignment purposes, it can now be surprising that the right hand side of an initializer and the 'var' no longer match in type. If you mouse over the variable name, you see both: the type and the statement that the flow state is or isn't null. If you mouse directly over var...you don't get that. We should update var accordingly with text similar to "The initial value is not null" and "The initial value may be null" similar to what we show when you mouse over the variable name.

(The suggested text is stolen from @sharwell's comment in #41008)

[peabnuts123]

What exactly is the magnitude of change needed here? Does C# the language need changing here? The way its compiled? Just the way it is analysed? I have found my way here after following various issues and IMO this is wildly confusing. I just thought this was a bug in vscode. Will this ever see the light of day?

[CyrusNajmabadi]

@peabnuts123 it just needs someone willing to do the work. If you're interested, we'd welcome a contribution. Thanks!

[ryzngard]

Yea, I'm happy to walk you through the thought I had for a fix. Early on there was some changes into how nullability worked with var, and design was still in flux. I think it's very stable now so this would be a good issue to take on