Open Radar

 
Summary:
When attempting to compile the attached Swift source code, the Swift complier crashes 100% of the time.

Steps to Reproduce:
Attempt to compile the attached swift file: swift state.swift

Expected Results:
Complier should successfully compile the file, or emit language errors indicating developer mistakes

Actual Results:
Complier crashes.

Regression:
swiftc -version
Apple Swift version 2.1.1 (swiftlang-700.1.101.15 clang-700.1.81)
Target: x86_64-apple-darwin15.3.0

xcodebuild -version
Xcode 7.2.1
Build version 7C1002


Notes:
Tested against Xcode 7.2, 7.2.1 versions of Swift compiler. I’ve attempted to distill this down as much as possible. It manifests itself as a playground crash (where I originally encountered it). Obviously, it also causes problems within normal iOS projects as well.

Crash log:
0  swift                    0x0000000109c12fbb llvm::sys::PrintStackTrace(__sFILE*) + 43
1  swift                    0x0000000109c136fb SignalHandler(int) + 379
2  libsystem_platform.dylib 0x00007fff9f42aeaa _sigtramp + 26
3  libsystem_platform.dylib 0x00007fff57f05558 _sigtramp + 3098388168
4  swift                    0x0000000107ed9707 swift::SILWitnessVisitor<(anonymous namespace)::SILGenConformance>::visitProtocolDecl(swift::ProtocolDecl*) + 999
5  swift                    0x0000000107ed6ee5 swift::Lowering::SILGenModule::getWitnessTable(swift::ProtocolConformance*) + 277
6  swift                    0x0000000107f265b0 (anonymous namespace)::SILGenType::emitType() + 1264
7  swift                    0x0000000107f2604e swift::Lowering::SILGenModule::visitNominalTypeDecl(swift::NominalTypeDecl*) + 30
8  swift                    0x0000000107eaebdb swift::Lowering::SILGenModule::emitSourceFile(swift::SourceFile*, unsigned int) + 779
9  swift                    0x0000000107eaf790 swift::SILModule::constructSIL(swift::ModuleDecl*, swift::SILOptions&, swift::FileUnit*, llvm::Optional<unsigned int>, bool, bool) + 928
10 swift                    0x0000000107eafb3d swift::performSILGeneration(swift::FileUnit&, swift::SILOptions&, llvm::Optional<unsigned int>, bool) + 109
11 swift                    0x0000000107d03992 performCompile(swift::CompilerInstance&, swift::CompilerInvocation&, llvm::ArrayRef<char const*>, int&) + 11442
12 swift                    0x0000000107d00ad3 frontend_main(llvm::ArrayRef<char const*>, char const*, void*) + 2691
13 swift                    0x0000000107cfd154 main + 2324
14 libdyld.dylib            0x00007fff97bc55ad start + 1
15 libdyld.dylib            0x000000000000000f start + 1749264995
Stack dump:
0.	Program arguments: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swift -frontend -c -primary-file state.swift -target x86_64-apple-darwin15.3.0 -enable-objc-interop -sdk /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk -color-diagnostics -module-name state -o /var/folders/lf/by9b55r91tz5cm_9mm98c5kr0000gq/T/state-40e0f6.o 
<unknown>:0: error: unable to execute command: Segmentation fault: 11
<unknown>:0: error: compile command failed due to signal (use -v to see invocation)