Open Radar

 
Summary:
When endIndex is less than startIndex,
Rather than iterating the values from startIndex to endIndex,
Instead the range generator always adds 1 to startIndex.

The generator silently overflows and wraps around before reaching the endIndex.

Steps to Reproduce:
for i in 0..<Int8(-1) { println(i) }

Expected Results:
The only value printed is "0", consistent with range [0, -1) including only the value 0.

The values in the range are iterated, from startIndex up to but not including endIndex.

Iteration should not be able to advance beyond the bounds of the underlying integral type. If nothing else, Swift's overflow-safety should cause an exception when we hit the end of the representable values.

Actual Results:
The values printed are: 0, 1, …, 127, -128, -127, …, -2.

The generator's next() function always returns the current value + 1, rather than + or - 1 per the direction of the range.

Overflow is silent.

(Issuing a for-in print gets really ugly when the int-type is 64 bits.)

Version:
Xcode 6.0
Build version 6A254o

ProductName:	Mac OS X
ProductVersion:	10.9.4
BuildVersion:	13E28

Swift version 1.0 (swift-600.0.38.7)
Target: x86_64-apple-darwin13.3.0


Notes:
Likely related to <rdar://17559710>.