SwiftUI resultBuilder foreach

'm trying to write my own stack, and the issue I'm encountering is how to get the child content of a ForEach.

//
//  ContentView.swift
//  test
//
//  Created by cnsinda on 2025/10/18.
//

import SwiftUI

public struct MyStack<Content: View>: View {
    var content: [Content]

    public init(@MyStackBuilder<Content> content: @escaping () -> [Content]) {
        self.content = content()
    }

    public var body: some View {
        VStack {
             // I expect to get 9, but it always returns 1.
            Text("count:\(content.count)")
        }
    }
}

@resultBuilder public enum MyStackBuilder<Value: View> {
    static func buildBlock() -> [Value] {
        []
    }

    public static func buildBlock(_ components: Value...) -> [Value] {
        components
    }

    public static func buildBlock(_ components: [Value]...) -> [Value] {
        components.flatMap {
            $0
        }
    }

    // hit
    public static func buildExpression(_ expression: Value) -> [Value] {
        [expression]
    }

    public static func buildArray(_ components: [[Value]]) -> [Value] {
        components.flatMap { $0 }
    }

    static func buildFinalResult(_ components: [Value]) -> [Value] {
        components
    }

    public static func buildExpression(_ expression: ForEach<[Int], Int, Value>) -> [Value] {
        expression.data.flatMap { index in
            [expression.content(index)]
        }
    }

    public static func buildEither(first: [Value]) -> [Value] {
        return first
    }

    public static func buildEither(second: [Value]) -> [Value] {
        return second
    }

    public static func buildIf(_ element: [Value]?) -> [Value] {
        return element ?? []
    }
}

struct ContentView: View {
    var body: some View {
        ZStack {
            MyStack {
                ForEach([100, 110, 120, 130, 140, 150, 160, 170, 180], id: \.self) {
                    item in
                    Rectangle().frame(width: item, height: 20).padding(10)
                }
            }
        }
        .frame(width: 600, height: 600)
    }
}

My expectation is to get each individual Rectangle(), but the actual result is that the entire ForEach is treated as a single View. What should I do?