[stdlib] Unsafe[Mutable]Pointer: Add support for non-copyable Pointee types

Author: lorentey

stdlib/public/Cxx/UnsafeCxxIterators.swift

@@ -18,12 +18,13 @@
 ///
 /// - SeeAlso: https://en.cppreference.com/w/cpp/named_req/InputIterator
 public protocol UnsafeCxxInputIterator: Equatable {
-  associatedtype Pointee
+  associatedtype Pointee: ~Copyable
 
   /// Returns the unwrapped result of C++ `operator*()`.
   ///
   /// Generally, Swift creates this property automatically for C++ types that
   /// define `operator*()`.
+  @_borrowed
   var pointee: Pointee { get }
 
   /// Returns an iterator pointing to the next item in the sequence.
@@ -33,19 +34,23 @@ public protocol UnsafeCxxInputIterator: Equatable {
   func successor() -> Self
 }
 
-extension UnsafePointer: UnsafeCxxInputIterator {}
+extension UnsafePointer: UnsafeCxxInputIterator
+where Pointee: ~Copyable {}
 
-extension UnsafeMutablePointer: UnsafeCxxInputIterator {}
+extension UnsafeMutablePointer: UnsafeCxxInputIterator
+where Pointee: ~Copyable {}
 
 extension Optional: UnsafeCxxInputIterator where Wrapped: UnsafeCxxInputIterator {
   public typealias Pointee = Wrapped.Pointee
 
   @inlinable
   public var pointee: Pointee {
-    if let value = self {
-      return value.pointee
+    _read {
+      guard let value = self else {
+        fatalError("Could not dereference nullptr")
+      }
+      yield value.pointee
     }
-    fatalError("Could not dereference nullptr")
   }
 
   @inlinable
@@ -58,10 +63,12 @@ extension Optional: UnsafeCxxInputIterator where Wrapped: UnsafeCxxInputIterator
 }
 
 public protocol UnsafeCxxMutableInputIterator: UnsafeCxxInputIterator {
+  @_borrowed
   override var pointee: Pointee { get set }
 }
 
-extension UnsafeMutablePointer: UnsafeCxxMutableInputIterator {}
+extension UnsafeMutablePointer: UnsafeCxxMutableInputIterator
+where Pointee: ~Copyable {}
 
 /// Bridged C++ iterator that allows computing the distance between two of its
 /// instances, and advancing an instance by a given number of elements.
@@ -77,10 +84,14 @@ public protocol UnsafeCxxRandomAccessIterator: UnsafeCxxInputIterator {
   static func +=(lhs: inout Self, rhs: Distance)
 }
 
-extension UnsafePointer: UnsafeCxxRandomAccessIterator {}
+extension UnsafePointer: UnsafeCxxRandomAccessIterator
+where Pointee: ~Copyable {}
 
-extension UnsafeMutablePointer: UnsafeCxxRandomAccessIterator {}
+extension UnsafeMutablePointer: UnsafeCxxRandomAccessIterator
+where Pointee: ~Copyable {}
 
-public protocol UnsafeCxxMutableRandomAccessIterator: UnsafeCxxRandomAccessIterator, UnsafeCxxMutableInputIterator {}
+public protocol UnsafeCxxMutableRandomAccessIterator:
+UnsafeCxxRandomAccessIterator, UnsafeCxxMutableInputIterator {}
 
-extension UnsafeMutablePointer: UnsafeCxxMutableRandomAccessIterator {}
+extension UnsafeMutablePointer: UnsafeCxxMutableRandomAccessIterator
+where Pointee: ~Copyable {}

stdlib/public/Synchronization/AtomicPointers.swift

@@ -15,7 +15,7 @@
 //===----------------------------------------------------------------------===//
 
 @available(SwiftStdlib 6.0, *)
-extension UnsafePointer: AtomicRepresentable {
+extension UnsafePointer: AtomicRepresentable where Pointee: ~Copyable {
   /// The storage representation type that `Self` encodes to and decodes from
   /// which is a suitable type when used in atomic operations.
   @available(SwiftStdlib 6.0, *)
@@ -65,7 +65,7 @@ extension UnsafePointer: AtomicRepresentable {
 }
 
 @available(SwiftStdlib 6.0, *)
-extension UnsafePointer: AtomicOptionalRepresentable {
+extension UnsafePointer: AtomicOptionalRepresentable where Pointee: ~Copyable {
   /// The storage representation type that encodes to and decodes from
   /// `Optional<Self>` which is a suitable type when used in atomic operations
   /// on `Optional`.
@@ -121,7 +121,7 @@ extension UnsafePointer: AtomicOptionalRepresentable {
 //===----------------------------------------------------------------------===//
 
 @available(SwiftStdlib 6.0, *)
-extension UnsafeMutablePointer: AtomicRepresentable {
+extension UnsafeMutablePointer: AtomicRepresentable where Pointee: ~Copyable {
   /// The storage representation type that `Self` encodes to and decodes from
   /// which is a suitable type when used in atomic operations.
   @available(SwiftStdlib 6.0, *)
@@ -171,7 +171,8 @@ extension UnsafeMutablePointer: AtomicRepresentable {
 }
 
 @available(SwiftStdlib 6.0, *)
-extension UnsafeMutablePointer: AtomicOptionalRepresentable {
+extension UnsafeMutablePointer: AtomicOptionalRepresentable
+where Pointee: ~Copyable {
   /// The storage representation type that encodes to and decodes from
   /// `Optional<Self>` which is a suitable type when used in atomic operations
   /// on `Optional`.

stdlib/public/core/MigrationSupport.swift

@@ -425,7 +425,9 @@ extension UnsafeMutableRawPointer: _CustomPlaygroundQuickLookable {
   }
 }
 
-extension UnsafePointer: _CustomPlaygroundQuickLookable {
+extension UnsafePointer: _CustomPlaygroundQuickLookable
+where Pointee: ~Copyable // FIXME: This should not be necessary
+{
   private var summary: String {
     let ptrValue = UInt64(bitPattern: Int64(Int(Builtin.ptrtoint_Word(_rawValue))))
     return ptrValue == 0 
@@ -439,7 +441,9 @@ extension UnsafePointer: _CustomPlaygroundQuickLookable {
   }
 }
 
-extension UnsafeMutablePointer: _CustomPlaygroundQuickLookable {
+extension UnsafeMutablePointer: _CustomPlaygroundQuickLookable
+where Pointee: ~Copyable // FIXME: This should not be necessary
+{
   private var summary: String {
     let ptrValue = UInt64(bitPattern: Int64(Int(Builtin.ptrtoint_Word(_rawValue))))
     return ptrValue == 0 

stdlib/public/core/Pointer.swift

@@ -2,7 +2,7 @@
 //
 // This source file is part of the Swift.org open source project
 //
-// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Copyright (c) 2014 - 2024 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
@@ -30,8 +30,8 @@ public protocol _Pointer
 , _BitwiseCopyable {
   /// A type that represents the distance between two pointers.
   typealias Distance = Int
-  
-  associatedtype Pointee
+
+  associatedtype Pointee: ~Copyable
 
   /// The underlying raw pointer value.
   var _rawValue: Builtin.RawPointer { get }
@@ -336,6 +336,7 @@ extension Int {
   ///
   /// - Parameter pointer: The pointer to use as the source for the new
   ///   integer.
+  @_alwaysEmitIntoClient
   @_transparent
   public init<P: _Pointer>(bitPattern pointer: P?) {
     if let pointer = pointer {
@@ -354,6 +355,7 @@ extension UInt {
   ///
   /// - Parameter pointer: The pointer to use as the source for the new
   ///   integer.
+  @_alwaysEmitIntoClient
   @_transparent
   public init<P: _Pointer>(bitPattern pointer: P?) {
     if let pointer = pointer {