Xcode 15 Preview not working with generic nested view

Using Swift
, , , ,
1

It seem that Xcode preview compiler fail correctly parse generic and produce a "Failed to build" error:

Proposed example:

^^^^^^^^^^^^^^^^^^^^^^^^^^^

import CoreBluetooth
import SwiftUI

/// Not working in preview
struct NotWorkingView: View {
    var body: some View {
        InitialView<String>()
    }

    struct InitialView<S>: View where S: StringProtocol {
        var body: some View {
            NestedView()
        }

        struct NestedView: View {
            var body: some View {
                Text("Hello")
            }
        }
    }
}

struct ContentView_PreviewProviders: PreviewProvider {
    static var previews: some View {
        NotWorkingView()
    }
}

^^^^^^^^^^^^^^^^^^^^^^^^^^^

investigating the SampleView.1.preview-thunk.swift from ~/Library/Developer/Xcode/DerivedData/.../ directory, I found that compiler translate the above code into pre-compiled stage using typealias without considering the Generic condition-

^^^^^^^^^^^^^^^^^^^^^^^^^^^

...
extension NotWorking.InitialView.NestedView {
typealias InitialView = NotWorking.InitialView
typealias NestedView = NotWorking.InitialView.NestedView

    @_dynamicReplacement(for: body) private var __preview__body: some View {
        #sourceLocation(file: "/Users/giuseppe/Development/Private/Dev/MyPlayground/MyPlayground/SampleView.swift", line: 40)
                Text(__designTimeString("#32812.[2].[1].[1].[0].property.[0].[0].arg[0].value", fallback: "Hello"))
            
#sourceLocation()
    }
}

extension NotWorking.InitialView {
typealias InitialView = NotWorking.InitialView
typealias NestedView = NotWorking.InitialView.NestedView

    @_dynamicReplacement(for: body) private var __preview__body: some View {
        #sourceLocation(file: "/Users/giuseppe/Development/Private/Dev/MyPlayground/MyPlayground/SampleView.swift", line: 35)
            NestedView()
        
#sourceLocation()
    }
}

extension NotWorking {
    @_dynamicReplacement(for: body) private var __preview__body: some View {
        #sourceLocation(file: "/Users/giuseppe/Development/Private/Dev/MyPlayground/MyPlayground/SampleView.swift", line: 30)
        InitialView<String>()
    
#sourceLocation()
    }
}
...

^^^^^^^^^^^^^^^^^^^^^^^^^^^

Should be considered a compiler bug or I missed something in my code?

2

Here the Preview reported error:

== PREVIEW UPDATE ERROR:

CompileDylibError: Failed to build SampleView.swift

Compiling failed: reference to generic type 'NotWorking.InitialView' requires arguments in <...>

/Users/giuseppe/Library/Developer/Xcode/DerivedData/MyPlayground-avscbrxoycipyhbsfadustywnrmd/Build/Intermediates.noindex/> Previews/MyPlayground/Intermediates.noindex/MyPlayground.build/Debug-iphonesimulator/MyPlayground.build/Objects-normal/x86_64/> SampleView.1.preview-thunk.swift:35:35: error: reference to generic type 'NotWorking.InitialView' requires arguments in <...>
typealias NestedView = NotWorking.InitialView.NestedView
                                  ^
                                             <<#S: StringProtocol#>>
/Users/giuseppe/Development/Private/Dev/MyPlayground/MyPlayground/SampleView.swift:33:12: note: generic type 'InitialView' > declared here
    struct InitialView<S>: View where S: StringProtocol {
           ^
/Users/giuseppe/Library/Developer/Xcode/DerivedData/MyPlayground-avscbrxoycipyhbsfadustywnrmd/Build/Intermediates.noindex/> Previews/MyPlayground/Intermediates.noindex/MyPlayground.build/Debug-iphonesimulator/MyPlayground.build/Objects-normal/x86_64/> SampleView.1.preview-thunk.swift:21:34: error: ambiguous type name 'NestedView' in 'NotWorking.InitialView'
extension NotWorking.InitialView.NestedView {
          ~~~~~~~~~~~~~~~~~~~~~~ ^
/Users/giuseppe/Development/Private/Dev/MyPlayground/MyPlayground/SampleView.swift:38:16: note: found candidate with type > 'NotWorking.InitialView.NestedView'
        struct NestedView: View {
               ^
/Users/giuseppe/Library/Developer/Xcode/DerivedData/MyPlayground-avscbrxoycipyhbsfadustywnrmd/Build/Intermediates.noindex/> Previews/MyPlayground/Intermediates.noindex/MyPlayground.build/Debug-iphonesimulator/MyPlayground.build/Objects-normal/x86_64/> SampleView.1.preview-thunk.swift:35:11: note: found candidate with type '<<error type>>'
typealias NestedView = NotWorking.InitialView.NestedView
          ^
/Users/giuseppe/Library/Developer/Xcode/DerivedData/MyPlayground-avscbrxoycipyhbsfadustywnrmd/Build/Intermediates.noindex/> Previews/MyPlayground/Intermediates.noindex/MyPlayground.build/Debug-iphonesimulator/MyPlayground.build/Objects-normal/x86_64/> SampleView.1.preview-thunk.swift:23:47: error: ambiguous type name 'NestedView' in 'NotWorking.InitialView'
typealias NestedView = NotWorking.InitialView.NestedView
                       ~~~~~~~~~~~~~~~~~~~~~~ ^
/Users/giuseppe/Development/Private/Dev/MyPlayground/MyPlayground/SampleView.swift:38:16: note: found candidate with type > 'NotWorking.InitialView.NestedView'
        struct NestedView: View {
               ^
/Users/giuseppe/Library/Developer/Xcode/DerivedData/MyPlayground-avscbrxoycipyhbsfadustywnrmd/Build/Intermediates.noindex/> Previews/MyPlayground/Intermediates.noindex/MyPlayground.build/Debug-iphonesimulator/MyPlayground.build/Objects-normal/x86_64/> SampleView.1.preview-thunk.swift:35:11: note: found candidate with type '<<error type>>'
typealias NestedView = NotWorking.InitialView.NestedView
          ^
3

This is indeed a bug! Could you please file a report with this reproducer? (feedback.apple.com)

4

Done @ Feedback Assistant