This seems to have been broken since Swift 5.1 (that shipped in Xcode 11 as part of macOS 10.15, iOS 13, watchOS 6, and tvOS 13).

It may be worth making sure the fix deploys back to these earlier OS releases (if possible). As it stands, it is not safe to call wCSIA on Arrays.

The same issue applies to the `withUnsafeBufferPointer` method, and probably all other methods that provide direct access to the array's underlying storage.

@swift-ci create

This was resolved by #37914 on the main branch. The fix is expected to deploy back to earlier releases, as long as the binary gets recompiled with a stdlib that contains this fix – although unfortunately this isn't 100% guaranteed.

I'll try to cherry-pick this to the 5.5 release branch too.

Did this fix make it into the 5.5 release? I'm seeing an almost identical fatal error when calling difference(from: …) on an NSArray associated with an Objective-C instance:

Swift/ArrayBuffer.swift:319: Fatal error: unsupported

Edit: on further testing, the same code works fine on macOS 12.0b9, so perhaps this is an issue of back deployment. I'll see if I can create a minimal reproduction and file a new issue - sorry for the noise!