Swift compiler hang: nested pattern match with type-cast

Originator:klazuka
Number:rdar://17970286 Date Originated:8/9/2014
Status:Open Resolved:
Product:Xcode Product Version:Xcode6-beta5 (6A279r)
Classification:Serious Reproducible:Always
 
Summary:
The Swift compiler will hang when trying to compile a switch statement that does a nested pattern match with a type-cast. I have attached a playground file which demonstrates the problem, as well as callstack samples from Activity Monitor.

Steps to Reproduce:
See attached playground file. Specifically, write a switch statement that includes at least 2 cases that look like the following:

case .C(.A, let foo as String):


Expected Results:
The compiler should never hang

Actual Results:
The compiler hangs forever

Version:
Xcode6-beta5 (6A279r)
OSX 10.9.4 (13E28)

Notes:


Configuration:
Macbook pro running mavericks

Attachments:
'SwitchTypeCastBug.playground.zip', 'Sample of SourceKitService.txt' and 'Sample of com.apple.dt.Xcode.Playground.txt' were successfully uploaded.

Comments

The offending Swift code / playground

// Playground - noun: a place where people can play

import Foundation

enum Inner { case A case B }

enum Outer { case C(Inner, Any) }

let x = Outer.C(Inner.A, "hello")

switch x { case .C(.A, let foo as String): println("C/A string '(foo)'") case .C(.B, let foo as String): println("C/B string '(foo)'") default: println("default") }


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