RigidArray inclusion into StdLib

joehink · June 15, 2026, 2:57am

I'm a big fan of the new UniqueBox and similar types. I'm very excited about their inclusion in the StdLib in 6.4!

But it looks like RigidArray is limited to internal stdlib use. Why is that? Are there plans to expose this to user code?

github.com/swiftlang/swift

stdlib/public/core/RigidArray/RigidArray.swift

main

//===----------------------------------------------------------------------===//
//
// This source file is part of the Swift.org open source project
//
// Copyright (c) 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
// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
//
//===----------------------------------------------------------------------===//

/// A fixed capacity, heap allocated, noncopyable array of potentially
/// noncopyable elements.
///
/// `RigidArray` instances are created with a specific maximum capacity. Elements
/// can be added to the array up to that capacity, but no more: trying to add an
/// item to a full array results in a runtime trap.
///
///      var items = RigidArray<Int>(capacity: 2)

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John_McCall · June 15, 2026, 3:28am

It was not approved as part of SE-0527; see the announcement.