InputMultispan and OutputMultispan + basic adoption in RigidArray and UniqueArray

CMakeLists.txt

@@ -50,6 +50,7 @@ set(collections_swift_flags
   "-enable-upcoming-feature MemberImportVisibility"
   "-enable-experimental-feature BuiltinModule"
   "-enable-experimental-feature Lifetimes"
+  "-enable-experimental-feature LifetimeDependence"
   "-enable-experimental-feature InoutLifetimeDependence"
 )
 foreach(flag ${collections_swift_flags})

Package.swift

@@ -104,6 +104,7 @@ let extraSettings: [SwiftSetting] = [
 //  .strictMemorySafety(),
   .enableExperimentalFeature("BuiltinModule"),
   .enableExperimentalFeature("Lifetimes"),
+  .enableExperimentalFeature("LifetimeDependence"),
   .enableExperimentalFeature("InoutLifetimeDependence"),
   .enableExperimentalFeature("SuppressedAssociatedTypes"),
   .enableExperimentalFeature("AddressableParameters"),

Sources/ContainersPreview/CMakeLists.txt

@@ -24,6 +24,7 @@ endif()
 
 target_sources(${module_name} PRIVATE
   "Extensions/OutputSpan+Extras.swift"
+  "Extensions/OutputMultispan+Extras.swift"
   "Extensions/TemporaryAllocation.swift"
   "Protocols/BorrowingIteratorProtocol.swift"
   "Protocols/BorrowingSequence.swift"
@@ -37,5 +38,7 @@ target_sources(${module_name} PRIVATE
   "Types/Box.swift"
   "Types/Inout.swift"
   "Types/InputSpan.swift"
+  "Types/InputMultispan.swift"
   "Types/Shared.swift"
+  "Types/OutputMultispan.swift"
 )

Sources/ContainersPreview/Extensions/OutputMultispan+Extras.swift

@@ -0,0 +1,71 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift Collections open source project
+//
+// Copyright (c) 2024 - 2026 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+//
+//===----------------------------------------------------------------------===//
+
+#if compiler(>=6.2) && COLLECTIONS_UNSTABLE_CONTAINERS_PREVIEW
+
+#if !COLLECTIONS_SINGLE_MODULE
+import InternalCollectionsUtilities
+#endif
+
+@available(SwiftStdlib 5.0, *)
+extension RigidArray where Element: ~Copyable {
+  @_alwaysEmitIntoClient
+  public mutating func append<E: Error>(
+    addingCount newItemCount: Int,
+    initializingWith initializer: @escaping (inout OutputMultispan<Element>) async throws(E) -> Void
+  ) async throws(E) {
+    precondition(newItemCount >= 0, "Cannot add a negative number of items")
+    precondition(freeCapacity >= newItemCount, "RigidArray capacity overflow")
+    let buffer = _freeSpace._extracting(first: newItemCount)
+    var span = OutputSpan(buffer: buffer, initializedCount: 0)
+    defer {
+      _count &+= span.finalize(for: buffer)
+      span = OutputSpan()
+    }
+    var multiSpan = OutputMultispan<Element>()
+    multiSpan._appendSpan(&span)
+    return try await initializer(&multiSpan)
+  }
+
+  @inlinable
+  public init<E: Error>(
+    capacity: Int,
+    initializingWith body: @escaping (inout OutputMultispan<Element>) throws(E) -> Void
+  ) async throws(E) {
+    self.init(capacity: capacity)
+    try await append(addingCount: capacity, initializingWith: body)
+  }
+}
+
+@available(SwiftStdlib 5.0, *)
+extension UniqueArray where Element: ~Copyable {
+  @_alwaysEmitIntoClient
+  public mutating func append<E: Error>(
+    addingCount newItemCount: Int,
+    initializingWith initializer: @escaping (inout OutputMultispan<Element>) async throws(E) -> Void
+  ) async throws(E) {
+    _ensureFreeCapacity(newItemCount)
+    return try await _storage.append(
+      addingCount: newItemCount,
+      initializingWith: initializer)
+  }
+
+  @inlinable
+  public init<E: Error>(
+    capacity: Int,
+    initializingWith body: @escaping (inout OutputMultispan<Element>) throws(E) -> Void
+  ) async throws(E) {
+    self.init(capacity: capacity)
+    try await append(addingCount: capacity, initializingWith: body)
+  }
+}
+
+#endif