var and type apparent for nullable types

[brinko99]

var and type apparent for nullable types

[CyrusNajmabadi]

var hides the fact that the variable is nullable

This would prevent 'var' from ever being used. As far as the language is concerned, 'var' is always nullable for reference types.

We also cannot change this as that will cause build breaks for anyone upgrading.

[brinko99]

Thanks for your response. Can you clarify? I don't understand your comment "prevent 'var' from ever being used".

I'm imagining "apparent" logic that could act as such for different signatures:

Assembly GetEntryAssembly()' -- Type is apparent, use var Assembly? GetEntryAssembly()' -- Type is not apparent, use explicit type

Per your second point, as compatibility is a concern, I suggest a new style option that requires an explicit type used when the type is nullable in a nullable context. This could be defaulted to off to ensure compatibility.

[CyrusNajmabadi]

Can you clarify? I don't understand your comment "prevent 'var' from ever being used".

in all place where you use 'var' with a reference type, the type is T? from teh perspective of the language/compiler.

You said:

In our opinion, nullable types should not be considered 'apparent' when in the nullable context.

That would mean that if you turned on csharp_style_var_when_type_is_apparent we would not ever suggest 'var' for a reference type in nullable contexts, which would be massively bad :)

[CyrusNajmabadi]

Per your second point, as compatibility is a concern, I suggest a new style option that requires an explicit type used when the type is nullable in a nullable context

In hte past we've rejected this idea as every single developer has a different view on this topic. We went with the majority view when designing the option and have stuck with that to keep broad consistency across the ecosystem. We do not think knobs/options helps here.