[stdlib] Uncheck pointers' conf to BitwiseCopyable

The pitch calls for such types to obstruct inference of _BitwiseCopyable
in aggregates containing them.

Author: nate-chandler

stdlib/public/core/BridgeObjectiveC.swift

@@ -407,7 +407,7 @@ public func _getBridgedNonVerbatimObjectiveCType<T>(_: T.Type) -> Any.Type?
 /// already have writeback-scoped lifetime.
 @frozen
 public struct AutoreleasingUnsafeMutablePointer<Pointee /* TODO : class */>
-  :  _Pointer {
+  :  _Pointer, @unchecked _BitwiseCopyable {
 
   public let _rawValue: Builtin.RawPointer
 

stdlib/public/core/CTypes.swift

@@ -142,7 +142,7 @@ public typealias CBool = Bool
 /// Opaque pointers are used to represent C pointers to types that
 /// cannot be represented in Swift, such as incomplete struct types.
 @frozen
-public struct OpaquePointer {
+public struct OpaquePointer : @unchecked _BitwiseCopyable {
   @usableFromInline
   internal var _rawValue: Builtin.RawPointer
 

stdlib/public/core/UnsafeBufferPointer.swift.gyb

@@ -30,7 +30,8 @@
 /// collection with an `${Self}` instance copies the instances out of the
 /// referenced memory and into the new collection.
 @frozen // unsafe-performance
-public struct Unsafe${Mutable}BufferPointer<Element> {
+public struct Unsafe${Mutable}BufferPointer<Element> 
+  : @unchecked _BitwiseCopyable {
 
   @usableFromInline
   let _position: Unsafe${Mutable}Pointer<Element>?

stdlib/public/core/UnsafePointer.swift

@@ -205,7 +205,7 @@
 ///       let numberPointer = UnsafePointer<Int>(&number)
 ///       // Accessing 'numberPointer' is undefined behavior.
 @frozen // unsafe-performance
-public struct UnsafePointer<Pointee>: _Pointer {
+public struct UnsafePointer<Pointee>: _Pointer, @unchecked _BitwiseCopyable {
 
   /// A type that represents the distance between two pointers.
   public typealias Distance = Int
@@ -578,7 +578,8 @@ public struct UnsafePointer<Pointee>: _Pointer {
 ///       let numberPointer = UnsafeMutablePointer<Int>(&number)
 ///       // Accessing 'numberPointer' is undefined behavior.
 @frozen // unsafe-performance
-public struct UnsafeMutablePointer<Pointee>: _Pointer {
+public struct UnsafeMutablePointer<Pointee>
+  : _Pointer, @unchecked _BitwiseCopyable {
 
   /// A type that represents the distance between two pointers.
   public typealias Distance = Int

stdlib/public/core/UnsafeRawPointer.swift

@@ -169,7 +169,7 @@
 ///       let numberPointer = UnsafeRawPointer(&number)
 ///       // Accessing 'numberPointer' is undefined behavior.
 @frozen
-public struct UnsafeRawPointer: _Pointer {
+public struct UnsafeRawPointer: _Pointer, @unchecked _BitwiseCopyable {
 
   public typealias Pointee = UInt8
 
@@ -727,7 +727,7 @@ extension UnsafeRawPointer {
 ///       let numberPointer = UnsafeMutableRawPointer(&number)
 ///       // Accessing 'numberPointer' is undefined behavior.
 @frozen
-public struct UnsafeMutableRawPointer: _Pointer {
+public struct UnsafeMutableRawPointer: _Pointer, @unchecked _BitwiseCopyable {
 
   public typealias Pointee = UInt8
 

test/SourceKit/DocSupport/doc_clang_module.swift.response

@@ -5654,6 +5654,11 @@ var FooSubUnnamedEnumeratorA1: Int { get }
         key.kind: source.lang.swift.ref.protocol,
         key.name: "_Pointer",
         key.usr: "s:s8_PointerP"
+      },
+      {
+        key.kind: source.lang.swift.ref.protocol,
+        key.name: "_BitwiseCopyable",
+        key.usr: "s:s16_BitwiseCopyableP"
       }
     ]
   },