Nil coalescing operator ambiguity

[skreberem]

Nil coalescing operator overload for GraphQLNullable results in ambiguity errors where type is not explicitly specified.

Example:

let width = rect?.width ?? 0

Error:

Ambiguous use of operator '??'

[gsapienza]

I am also experiencing this

[calvincestari]

I don't know if there is any good way around this. I think it's caused by the fact that GraphQLNullable is simply a wrapper around many supported types. So the compiler is correct in telling you that it cannot infer which one it should use without conclusively knowing the property type.

It's resolved by specifying the type of width but I can see how that would be annoying if this syntax is used in many places of your existing codebase. Any suggestions?

[milowyner]

Same issue here, and the codebase I'm working on has a lot of places where nil coalescing is used, so I just had to comment out the operator overload in GraphQLNullable, which isn't a great solution.

[calvincestari]

Instead of commenting it out, try adding @_disfavoredOverload above the operator overload and see if it changes how the compiler treats the ambiguity.

[milowyner]

Ah thanks. That also works, and it feels like a better temporary solution. I was going to say they should add this to the SDK, but it seems that it's not recommended outside the compiler and standard library 😕 https://github.com/apple/swift/blob/main/docs/ReferenceGuides/UnderscoredAttributes.md

[calvincestari]

I'm glad to hear it improves the issue, I'm going to go ahead with making that the fix and get it into 1.0.4. We already use a couple other @_ attributes in other places so we're comfortable using those for now. Thanks for trying it in your code, I appreciate the time.