Lincoln Wu CrystDragon

Async/Await for Swift

Proposal: SE-XXXX
Authors: Chris Lattner, Joe Groff

Introduction

Modern Cocoa development involves a lot of asynchronous programming using closures and completion handlers, but these APIs are hard to use. This gets particularly problematic when many asynchronous operations are used, error handling is required, or control flow between asynchronous calls gets complicated. This proposal describes a language extension to make this a lot more natural and less error prone.

This paper introduces a first class Coroutine model to Swift. Functions can opt into to being async, allowing the programmer to compose complex logic involving asynchronous operations, leaving the compiler in charge of producing the necessary closures and state machines to implement that logic.

Compile Time Constant Expressions for Swift

Proposal: SE-NNNN
Authors: Marc Rasi, Chris Lattner
Review Manager: TBD
Status: Awaiting implementation

Swift-evolution thread: https://forums.swift.org/t/pitch-compile-time-constant-expressions-for-swift/12879

Introduction

LLDB Custom Commands

[LLDB] can be customized with ~/.lldbinit to run commands and to load more commands from shell and python scripts. One option is [Chisel] which provides several commands which can be used to debug an software running in Xcode.

It is critical that LLDB can process the commands in ~/.lldbinit successfully as a failure can cause the debugger to fail or run in an undefined way. The configuration listed in this Gist prints a message at the start and end so that when the debugger is run it is clear if any errors are shown in the Xcode console they are related to LLDB.

WWDC                                2006  2007  2008  2009
2010 2011 2012 2013 2014

Preventing Data Races in the Swift Concurrency Model

One of the goals of the concurrency effort is to prevent data races. This document describes the approach taken to preventing data races overall, by categorizing the sources of data races and describing how they are addressed with other proposals in the Swift Concurrency effort.

Data races

A data race occurs when two threads access the same memory concurrently and at least one of the accesses can change the value. Within the safe subset of Swift (e.g., ignoring the use of UnsafeMutablePointer and related types), the memory in question is always a stored property. There are several different categories of stored properties that need to be considered for data races:

Global and static stored properties:

	https://developer.apple.com/videos/wwdc/2015/?id=101 101 Keynote
	https://developer.apple.com/videos/wwdc/2015/?id=102 102 Platforms State of the Union
	https://developer.apple.com/videos/wwdc/2015/?id=103 103 Apple Design Awards
	https://developer.apple.com/videos/wwdc/2015/?id=104 104 What's New in Xcode
	https://developer.apple.com/videos/wwdc/2015/?id=105 105 Introducing WatchKit for watchOS 2
	https://developer.apple.com/videos/wwdc/2015/?id=106 106 What's New in Swift
	https://developer.apple.com/videos/wwdc/2015/?id=107 107 What's New in Cocoa Touch
	https://developer.apple.com/videos/wwdc/2015/?id=108 108 Building Watch Apps
	https://developer.apple.com/videos/wwdc/2015/?id=112 112 Think Audacious
	https://developer.apple.com/videos/wwdc/2015/?id=201 201 iOS Accessibility

	@objc func _needsDoubleUpdateConstraintsPass() -> Bool {
	return true
	}

	override var intrinsicContentSize: CGSize {
	return attributedText?.size(forWidth: (engineBounds ?? bounds).width) ?? .zero
	}

	var engineBounds: CGRect? {
	let objcSelector = "_nsis_compatibleBoundsInEngine:")

	import UIKit

	/// A validation rule for text input.
	public enum TextValidationRule {
	/// Any input is valid, including an empty string.
	case noRestriction
	/// The input must not be empty.
	case nonEmpty
	/// The enitre input must match a regular expression. A matching substring is not enough.
	case regularExpression(NSRegularExpression)

	extension Collection {
	func parallelMap<T>(
	parallelism requestedParallelism: Int? = nil,
	_ transform: @escaping (Element) async throws -> T
	) async throws -> [T] {
	let defaultParallelism = 2
	let parallelism = requestedParallelism ?? defaultParallelism

	let n = self.count
	if n == 0 {