swift_allocEmptyBox missing in Embedded Swift

[TeamPuzel]

Description

No response

Reproduction

I tried to use this:

public struct EmptyDrawable: Drawable {
    public var width: Int { 0 }
    public var height: Int { 0 }
    public init() {}
    public subscript(x: Int, y: Int) -> Color { .clear }
}

In itself it's nothing unusual, besides being a zero sized type.

The problem seems to be caused by this however:

public extension Drawable where Self: ~Copyable {
    var lazy: LazyDrawable { consuming get { .init(self) } }
}

public final class LazyDrawable: Drawable {
    private let initializer: () -> Image
    public private(set) lazy var inner: Image = self.initializer()
    public let width: Int
    public let height: Int
    
    private init(_ initializer: @escaping () -> Image, width: Int, height: Int) {
        self.initializer = initializer
        self.width = width
        self.height = height
    }
    
    public convenience init(_ inner: consuming some Drawable & ~Copyable) {
        self.init({ inner.flatten() }, width: inner.width, height: inner.height)
    }
    
    public subscript(x: Int, y: Int) -> Color {
        inner[x, y]
    }
}

@resultBuilder
public struct FlatteningDrawableBuilder {
    public static func buildPartialBlock(first: consuming some Drawable & ~Copyable) -> [LazyDrawable] { [first.lazy] }
    
    public static func buildPartialBlock(first: [LazyDrawable]) -> [LazyDrawable] { first }

    public static func buildPartialBlock(accumulated: [LazyDrawable], next: consuming some Drawable & ~Copyable) -> [LazyDrawable] {
        var acc = accumulated
        acc.append(next.lazy)
        return acc
    }
    
    public static func buildArray(_ components: [[LazyDrawable]]) -> [LazyDrawable] { components.joined() }
}

I assume Swift is trying to "allocate" space for the escaping capture of the zero sized struct.

This causes linking to fail because swift_allocEmptyBox does not exist.

Expected behavior

I expected the symbol to exist, much like the other class allocation functions. This one seems to have been omitted.

Environment

Apple Swift version 6.2-dev (LLVM 3a02857b159678d, Swift c91e295)
Target: arm64-apple-macosx15.0
Build config: +assertions

Additional information

No response