Add init TypeConformance implementation

Sources/OpenSwiftUI/Core/Runtime/ProtocolDescriptor.swift

@@ -0,0 +1,41 @@
+//
+//  ProtocolDescriptor.swift
+//  OpenSwiftUI
+//
+//  Audited for RELEASE_2021
+//  Status: WIP
+
+internal import COpenSwiftUI
+
+// MARK: - ProtocolDescriptor
+
+protocol ProtocolDescriptor {
+    static var descriptor: UnsafeRawPointer { get }
+}
+
+// MARK: - TupleDescriptor
+
+protocol TupleDescriptor: ProtocolDescriptor {
+    static var typeCache: [ObjectIdentifier: TupleTypeDescription<Self>] { get set }
+}
+
+extension TupleDescriptor where Self == ViewDescriptor {
+//    static func tupleDescription(__C.AGTupleType) -> SwiftUI.TupleTypeDescription<A>
+}
+
+// MARK: - TupleTypeDescription
+
+struct TupleTypeDescription<PD: ProtocolDescriptor> {
+    let contentTypes: [(Int, TypeConformance<PD>)]
+}
+
+// MARK: - ViewDescriptor
+
+struct ViewDescriptor: TupleDescriptor {
+    static var descriptor: UnsafeRawPointer {
+        _viewProtocolDescriptor()
+    }
+
+    // FIXME
+    static var typeCache: [ObjectIdentifier : TupleTypeDescription<ViewDescriptor>] = [:]
+}

Sources/OpenSwiftUI/Core/Runtime/TypeConformance.swift

@@ -0,0 +1,30 @@
+//
+//  TypeConformance.swift
+//  OpenSwiftUI
+//
+//  Audited for RELEASE_2021
+//  Status: Complete
+
+struct TypeConformance<PD: ProtocolDescriptor> {
+    var metadata: UnsafeRawPointer
+    var conformance: UnsafeRawPointer
+
+    init?(_ type: Any.Type) {
+        guard let conformance = swiftConformsToProtocol(type, PD.descriptor) else {
+            return nil
+        }
+        self.metadata = unsafeBitCast(type, to: UnsafeRawPointer.self)
+        self.conformance = conformance
+    }
+}
+
+func conformsToProtocol(_ type: Any.Type, _ protocolDescriptor: UnsafeRawPointer) -> Bool {
+    swiftConformsToProtocol(type, protocolDescriptor) != nil
+}
+
+@_silgen_name("swift_conformsToProtocol")
+@inline(__always)
+private func swiftConformsToProtocol(
+    _ type: Any.Type,
+    _ protocolDescriptor: UnsafeRawPointer
+) -> UnsafeRawPointer?

Sources/OpenSwiftUI/Core/View/ViewVisitor.swift

@@ -6,9 +6,9 @@
 //  Status: Complete
 
 protocol ViewVisitor {
-    func visit<V: View>(_ view: V)
+    mutating func visit<V: View>(_ view: V)
 }
 
 protocol ViewTypeVisitor {
-    func visit<V: View>(type: V.Type)
+    mutating func visit<V: View>(type: V.Type)
 }