[SR-5874] Runtime crash when using optional extension for closure

[swift-ci]

Previous ID	SR-5874
Radar	None
Original Reporter	mikekasp (JIRA User)
Type	Bug

Environment

Xcode 8.3.3 - Xcode 9

Additional Detail from JIRA

Votes	1
Component/s	Compiler
Labels	Bug, CompilerCrash, SILGen
Assignee	None
Priority	Medium

md5: 60e185a14e55cd47c86630bf1fa588d5

Issue Description:

The following code crashes always:

extension Optional { // where Wrapped == ()->() { // With this, no crash
    var method: Bool { return false }
}

class bar {
    var t: Bool = false {
        didSet {
            self.stuff(closure: { print("\(self)") })
        }
    }

     func stuff(closure: (() -> ())? = nil) {
        closure.method
    }
}

bar().t = false

[belkadan]

On near-master:

Assertion failed: (isPlusOne(SGF) && "Can not forward borrowed RValues"), function forwardInto, file /Volumes/Data/swift-public/swift/lib/SILGen/RValue.cpp, line 533.

1.  While emitting SIL for 'stuff(closure:)' at <stdin>:12:6

@jckarter? Or @gottesmm, for ownership?

[gottesmm]

This would be on me, but before we get to that mikekasp (JIRA User) are you using the actual toolchain in Xcode? Or are you using a custom toolchain?

[gottesmm]

The reason why I am asking is that I thought that assertion was not enabled in the actual Xcode toolchain.

[swift-ci]

Comment by Mike Kasperlik (JIRA)

Using the standard toolchain. Nothing custom.

[gottesmm]

Oh. I misunderstood. The assert is from a near master build by Jordan. Sorry for the noise!

[gottesmm]

@swift-ci sync