SILGen: Don't emit key path descriptors for properties with mutating getters [4.2]

[slavapestov]

Fixes https://bugs.swift.org/browse/SR-7176, rdar://problem/38439418.

[slavapestov]

@swift-ci Please test

[swift-ci]

Build failed
Swift Test Linux Platform
Git Sha - 96dc765

[slavapestov]

@parkera What happened here?

Foundation/NSArray.swift:670:20: error: value of type 'String' has no member 'hasSuffix'
19:07:33                 if filename.hasSuffix(ext) && filename.count > ext.count {
19:07:33                    ^~~~~~~~ ~~~~~~~~~

[parkera]

I don’t think we’ve changed this recently. Was there a change on String?

[slavapestov]

@milseman Any ideas?

[slavapestov]

@parkera In swift-4.2-branch, String.hasSuffix() is not defined on Linux. On master, it's implemented on both platforms. Can you remove the usage from Foundation?

[slavapestov]

The breakage was introduced by PR swiftlang/swift-corelibs-foundation#1404

[slavapestov]

@parkera Actually it looks like the method was removed from the Swift stdlib so this is our fault. rdar://38424188

[milseman]

@airspeedswift changed the hasPrefix/hasSuffix code recently. Is it available on Linux?

[jckarter]

Thanks Slava!

[airspeedswift]

It's that the PR that added them to the stdlib for Linux needed picking to 4.2 because corelibs-foundation doesn't have a 4.2 branch. Testing #15258 now.

[slavapestov]

@swift-ci Please test Linux