   ///
   /// - Precondition: `buffer` is an instance of a non-`@objc` class whose
   ///   `deinit` destroys its stored `Header` and any constructed `Element`s.
-  @inlinable // FIXME(sil-serialize-all)
+  @inlinable
   public init(unsafeBufferObject buffer: AnyObject) {
     ManagedBufferPointer._checkValidBufferClass(type(of: buffer))
 
     self._nativeBuffer = Builtin.unsafeCastToNativeObject(buffer)
   }
+
+  //===--- internal/private API -------------------------------------------===//
 
   /// Internal version for use by _ContiguousArrayBuffer where we know that we
   /// have a valid buffer class.

  ///   `bufferClass` is a non-`@objc` class with no declared stored
  ///   properties.  The `deinit` of `bufferClass` must destroy its
  ///   stored `Header` and any constructed `Element`s.
  @inlinable // FIXME(sil-serialize-all)
  internal init(
    bufferClass: AnyClass,
    minimumCapacity: Int

  }

  /// The actual number of bytes allocated for this object.
  @inlinable
  internal var _capacityInBytes: Int {
    return _swift_stdlib_malloc_size(_address)
  }

  /// The address of this instance in a convenient pointer-to-bytes form
  @inlinable
  internal var _address: UnsafeMutableRawPointer {
    return UnsafeMutableRawPointer(Builtin.bridgeToRawPointer(_nativeBuffer))
  }

  /// Offset from the allocated storage for `self` to the stored `Header`
  @inlinable
  internal static var _headerOffset: Int {
    _onFastPath()
    return _roundUp(
