Open Radar

 
Summary:


Steps to Reproduce:

1. Create a new Swift project.
2. Set `SWIFT_OPTIMIZATION_LEVEL = -O` in build setting or select Release build configuration in schema
3. Add a new file and paste the following code

public class A {
    public class func f() {
        B.f()
    }
}

class B {
    private class C {
        var this: C? = nil

        lazy var number: Int = {
            var local: C? = self
            let count = 0
            while let temp = local?.this {
                local = temp
            }
            return count
        }()

        func f() -> C {
            if number == 0 {
                return self
            }
            print(number)
            return self
        }
    }

    class func f() {
        let _ = C().f()
    }
}

4. Build

Expected Results:

Build finishes

Actual Results:

Build never ends, swift process CPU usage reaches 100%

Version/Build:

Xcode Version 9.0 (9A235)
macOS Sierra 10.12.6

Configuration: