withThrowingTaskGroup(of:returning:isolation:body:) transpiled incorrectly

[vdkdamian]

Issue

I have a function with the following Swift code:

var allProducts: [FNCProduct] = []

try await withThrowingTaskGroup(of: [FNCProduct].self) { pageProductsTaskGroup in
    // Some irrelevant code

    for try await pageProducts in pageProductsTaskGroup {
        allProducts.append(contentsOf: pageProducts)
    }
}

return allProducts

This gets transpiled to the following Kotlin code:

var allProducts: Array<FNCProduct> = arrayOf()

withThrowingTaskGroup(of = Array::class) { pageProductsTaskGroup ->
    // Some irrelevant code

    for (pageProducts in pageProductsTaskGroup.sref()) {
        allProducts.append(contentsOf = pageProducts)
    }
}

return@l allProducts.sref()

I'm getting an error from the compiler that refers to the following line:
allProducts.append(contentsOf = pageProducts)

Argument type mismatch: actual type is 'skip.lib.Array<CapturedType(*)>', but 'skip.lib.Sequence<funico.module.FNCProduct>' was expected.

Proposed solution:

I think this:

withThrowingTaskGroup(of = Array::class)

needs to change to this:

withThrowingTaskGroup(of = Array<FNCProduct>::class)

[marcprux]

This does appear to be a bug. For the time being, can you try working around it by wrapping the array in a struct? Like:

struct FNCProductCollection {
    var value: [FNCProduct] = []
}

var allProducts: FNCProductCollection = FNCProductCollection()

try await withThrowingTaskGroup(of: FNCProductCollection.self) { pageProductsTaskGroup in
    // Some irrelevant code

    for try await pageProducts in pageProductsTaskGroup.value {
        allProducts.value.append(contentsOf: pageProducts)
    }
}

return allProducts.value

[vdkdamian]

@marcprux The workaround is working. I'll use this for the moment.