[SR-11043] Crash on swift_getObjectType on usage of [weak self] or [unowned self] in closures after required initialziation in @objc convenience init

[swift-ci]

Previous ID	SR-11043
Radar	None
Original Reporter	grigorye (JIRA User)
Type	Bug

Attachment: Download

Environment

$ swift --version
Apple Swift version 5.0.1 (swiftlang-1001.0.82.4 clang-1001.0.46.5)
Target: x86_64-apple-darwin18.6.0

Reproducible with Xcode 10.2.1. Not reproducible with Swift 4.2.

Additional Detail from JIRA

Votes	0
Component/s	Compiler
Labels	Bug, 5.0Regression, RunTimeCrash
Assignee	None
Priority	Medium

md5: a5490d8dbd341cfc4cbf7da1454a5fc3

Issue Description:

After switching to Swift 5, we faced a crash in our code base that could be minimized down to the sample below.

The sample is tailored for execution in playground or for invocation with "swift xxx.swift". There's also an macOS project demonstrating the same crash (attached) (also available on GitHub). You can make iOS project and crash it with similar code as well.

This does crash:

import Foundation

class Foo {
    
    let foo: Int? = nil
    
    required init() {
    }
    
    @objc convenience init(x: Int) {
        self.init()
        _ = { [weak self] in
            _ = self
        }
    }
}

_ = Foo(x: 0)

Removal of @objc from the convenience initializer makes it not crash/behave as expected.
Removal of [weak self] from the closure makes it not crash/behave as expected.
Removal of property .foo seems to solve the problem as well.
It doesn't crash if you replace weak with unowned in the above example, but I believe that in our real case, it still crashes even with unowned.

Switching to Swift 4.2 or Swift 5.1 (swiftlang-1100.0.43.3 clang-1100.0.26.3) resolves the problem.

Moving the closure creation to a separate method like below makes it behave as expected:

class Foo {
    
    let foo: Int? = nil
    
    required init() {
    }
    
    @objc convenience init(x: Int) {
        self.init()
        self.bar()
    }
    
    private func bar() {
        _ = { [weak self] in
            _ = self
        }
    }
}

[belkadan]

Looks like this is fixed in Swift 5.1 already. @mikeash, does it ring a bell?

[mikeash]

It seems familiar but my search-fu is not strong enough to dig up a radar for it.