Open Radar

 
Summary:
Trying to narrow down the reduceLeft runtime crashes (and e.g. find a workaround) I instead found a bunch of compiler crashes. This is 2 of 3 so far.

TL;DR: Basically never call functions returned by functions taking functions passing them functions.


Steps to Reproduce:
1. Compile this.

public struct ReducibleOf<T> {
	public init<S : SequenceType where S.Generator.Element == T>(_ sequence: S) {}
	public func reduceLeft<Result>(recur: (ReducibleOf, Result, (Result, T) -> Result) -> Result) -> (ReducibleOf, Result, (Result, T) -> Result) -> Result {
		return { _, x, _ in x }
	}
}
func testReduction() {
	let sequence = [1, 2, 3, 4, 5, 6, 7, 8, 9]
	let reducible = ReducibleOf(sequence)
	var result = 0
	var take: (ReducibleOf<Int>, Int, (Int, Int) -> Int) -> Int = { reducible, initial, combine in
		result = initial
		return initial
	}
	var x = reducible.reduceLeft(take)(reducible, 0 as Int, { into, each in each })
}


Expected Results:
No crash.


Actual Results:
Crash.


Regression:
Instead of finding ways for this not to crash, all I’ve found is subtly different ways in which it might crash instead.


Notes:
This is apparently what I do with my Saturday nights.