MapAnnotationItem.swift

import SwiftUI
import MapKit

protocol MapAnnotationItem: Identifiable {
    associatedtype Annotation: MapAnnotationProtocol

    var coordinate: CLLocationCoordinate2D { get }
    var annotation: Annotation { get }
}

struct AnyMapAnnotationItem: MapAnnotationItem {
    let id: AnyHashable
    let coordinate: CLLocationCoordinate2D
    let annotation: AnyMapAnnotation
    let base: Any

    init<T: MapAnnotationItem>(_ base: T) {
        self.id = base.id
        self.coordinate = base.coordinate
        self.annotation = AnyMapAnnotation(base.annotation)
        self.base = base
    }
}