Swift: Trying to `swap` the same location is a fatal error

Originator:natecook
Number:rdar://22440946 Date Originated:26-Aug-2015 01:30 PM
Status:Open Resolved:
Product:Developer Tools Product Version:Xcode-beta (7A192o)
Classification:Serious Bug Reproducible:Always
 
Summary:
In the latest Swift beta, when calling `swap()` with the same value as both parameters, Swift throws a run-time error. This is a regression from previous versions of Swift, where such a call executed safely.

Steps to Reproduce:

1) Create a new playground (attached), and add the following code:

var a = [1, 2, 3, 4, 5]
swap(&a[0], &a[1])
swap(&a[0], &a[0])
print(a)

Expected Results:
The console should show [2, 1, 3, 4, 5]

Actual Results:
The playground shows a runtime error on the third line and the console reads “fatal error: swapping a location with itself is not supported”

Regression:
This has worked in all previous versions of Swift.

Comments


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