Xcode 7b3: Swiftc crashes when overriding hashValue in @objc subclass of Swift class

Originator:davidp
Number:rdar://21881476 Date Originated:7/17/15
Status:Open Resolved:
Product:Xcode Product Version:7.0 beta 3
Classification:crash Reproducible:always
 
The following code causes the Swift compiler to crash:

public func == (lhs: AbstractMessage, rhs: AbstractMessage) -> Bool
{
    return lhs.hashValue == rhs.hashValue
}
public class AbstractMessage:Hashable {
    public var hashValue: Int {
        get {
            return 7
        }
    }
}

@objc public class ObjectiveCMessage : AbstractMessage {
    override public var hashValue:Int {
        get {
            return 8
        }
    }
}

Removing the @objc decorator or removing the override of hashValue will avoid the crash.

Steps to Reproduce:
Compile the code above, either in a Playground or in an iOS project.

Expected Results:
Compiler to not crash.

Actual Results:
Compiler crashes with a failed assertion. Will attach the full log, but the assertion line is:

Assertion failed: (SILFn && "no IR function for swift-as-objc thunk"), function findSwiftAsObjCThunk, file /Library/Caches/com.apple.xbs/Sources/swiftlang/swiftlang-700.0.45/src/swift/lib/IRGen/GenObjC.cpp, line 931.

Same code compiles fine in 6.4, making this a regression.

Comments

This is fixed as of Xcode 7 beta 4, in that the compiler no longer crashes. It now reports the following error:

/Users/davidp/dev/SwiftCompilerCrashes/SwiftCompilerCrashes/SwiftObjcThunkAssertionFails.swift:23:14: error: only classes that inherit from NSObject can be declared @objc @objc public class ObjectiveCMessage : AbstractMessage {

I have marked it as Resolved from the reporter side in radar; will hold off on their official resolution before updating openradar.

By davidp at July 21, 2015, 9:24 p.m. (reply...)

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