Open Radar

 
Summary:

	Swiftc crashes with recursively defined indirect enums if they match a certain pattern.

Steps to Reproduce:

	Take this simple recursive binary tree:

	indirect enum PersistentBinaryTree<T> {
	    case Tail(left: PersistentBinaryTree, element: T, right: PersistentBinaryTree)
	    case Nil
	}
	=> Build successful

	Now add a function to it:

	indirect enum PersistentBinaryTree<T> {
	    case Tail(left: PersistentBinaryTree, element: T, right: PersistentBinaryTree)
	    case Nil
	    func foo() { }
	}

Expected Results:

	=> Build successful

Actual Results:

	=> Build failed. Command failed due to signal: Segmentation fault: 11

Regression:

	Here's the fun part: Change the order of parameters of the "Branch" case:

	indirect enum PersistentBinaryTree<T> {
	    case Tail(element: T, left: PersistentBinaryTree, right: PersistentBinaryTree)
	    case Nil
	    func foo() { }
	}
	=> Build successful

Notes:

	Same happens for PersistentList:

	indirect enum PersistentList<T> {
	    case Tail(head: T, tail: PersistentList)
	    case Empty
	    func foo() { }
	}
	=> Build successful

	indirect enum PersistentList<T> {
	    case Tail(tail: PersistentList, head: T)
	    case Empty
	    func foo() { }
	}
	=> Build failed. Command failed due to signal: Segmentation fault: 11

	Looks like indirect enums that have a recursive property at first position of a case AND functions segfault the compiler.

Update:

	Moving the "case Nil" above "case Branch(…)" (or "case Empty" above "case Tail(…)" respectively) makes the code compile, too.
	So for the segfault to trigger, a recursive property needs to be placed at the first position of the first case of a struct and it must have at least one function.