duplicates:

• SR-5310 unowned object crashes in noescape closures

Issue Description:

When compiling a project with Swift 3.2 we found a memory issue due to an (unnecessary) "unowned" keyword in a non-escaping block. I was able to create a minimal example which crashes with an EXC_BAD_ACCESS signal, both when compiled with Swift 3.2 and 4.0:

import Foundation

class A: NSObject {
    
    let b = B()
    
    func doSomething() {
        b.list.forEach { [unowned self] _ in
            print(self.b.list)
        }
    }
    
}

class B {
    let list = [1, 2]
}
A().doSomething()

The crash disappears, when A doesn't inherit from NSObject. I'm not 100% sure if this is a compiler issue or a programmer error but in my understanding adding [unowned self] shouldn't change anything in a non-escaping block.

When compiling the same code with Swift 3.1, it doesn't crash, so this is at least a compatibility issue.