Stored value type does not match pointer operand type!
 store %TSo13NSFileWrapperC* %167, i64* %17, align 8, !dbg !1425
 i64in function $s12XXXXXXXV20generateFileWrappersSDySSSo13NSFileWrapperCGyKF
 <unknown>:0: error: fatal error encountered during compilation; please submit a bug report ([https://swift.org/contributing/#reporting-bugs]) and include the project
 <unknown>:0: note: Broken function found, compilation aborted!
 Please submit a bug report ([https://swift.org/contributing/#reporting-bugs]) and include the project and the crash backtrace.
 Stack dump:
 0. Program arguments: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swift-frontend -frontend -c /Users/helge/dev/Swift/XXXXX
 1. Apple Swift version 5.4 (swiftlang-1205.0.26.9 clang-1205.0.19.55)
 2. Running pass 'Module Verifier' on function '@"$s12XXXXXXXXV20generateFileWrappersSDySSSo13NSFileWrapperCGyKF"'
 0 swift-frontend 0x0000000108be85f0 llvm::sys::PrintStackTrace(llvm::raw_ostream&) + 52
 1 swift-frontend 0x0000000108be7768 llvm::sys::RunSignalHandlers() + 128
 2 swift-frontend 0x0000000108be8bc0 SignalHandler(int) + 292
 3 libsystem_platform.dylib 0x0000000184ef9c44 _sigtramp + 56
 4 libsystem_pthread.dylib 0x0000000184eaeb98 pthread_kill + 292
 5 libsystem_c.dylib 0x0000000184df7460 abort + 104
 6 swift-frontend 0x0000000104b2a85c std::__1::__throw_length_error(char const*) + 0
 7 swift-frontend 0x0000000108b557d8 llvm::report_fatal_error(llvm::Twine const&, bool) + 252
 8 swift-frontend 0x0000000108b556dc llvm::report_fatal_error(llvm::Twine const&, bool) + 0
 9 swift-frontend 0x0000000108affe00 void llvm::VerifierSupport::CheckFailed<llvm::Instruction*, llvm::MDNode const*>(llvm::Twine const&, llvm::Instruction* const&, llvm::MDNode const* const&) + 0
 10 swift-frontend 0x0000000108aa47d8 llvm::FPPassManager::runOnFunction(llvm::Function&) + 1136
 11 swift-frontend 0x0000000108aa3d90 llvm::legacy::FunctionPassManagerImpl::run(llvm::Function&) + 96
 12 swift-frontend 0x0000000108aaa408 llvm::legacy::FunctionPassManager::run(llvm::Function&) + 336
 13 swift-frontend 0x0000000104e3edb0 swift::performLLVMOptimizations(swift::IRGenOptions const&, llvm::Module*, llvm::TargetMachine*) + 1484
 14 swift-frontend 0x0000000104e3fcc8 swift::performLLVM(swift::IRGenOptions const&, swift::DiagnosticEngine&, llvm::sys::SmartMutex<false>*, llvm::GlobalVariable*, llvm::Module*, llvm::TargetMachine*, llvm::StringRef, swift::UnifiedStatsReporter*) + 2460
 15 swift-frontend 0x0000000104b36080 performCompileStepsPostSILGen(swift::CompilerInstance&, std::__1::unique_ptr<swift::SILModule, std::__1::default_delete<swift::SILModule> >, llvm::PointerUnion<swift::ModuleDecl*, swift::SourceFile*>, swift::PrimarySpecificPaths const&, int&, swift::FrontendObserver*) + 3084
 16 swift-frontend 0x0000000104b280c8 swift::performFrontend(llvm::ArrayRef<char const*>, char const*, void*, swift::FrontendObserver*) + 5548
 17 swift-frontend 0x0000000104abd100 main + 1136
 18 libdyld.dylib 0x0000000184ecc420 start + 4
 error: Abort trap: 6 (in target 'XXXX' from project 'XXXX')
 

extension SomeStruct {
  func generateFileWrappers() throws -> [ String : FileWrapper ] {
    var wrappers = [ String : FileWrapper ]()
    
    for fragment in self.values {
      let wrapper = try self.wrapper(for      : fragment.attributedString,
                                     filename : fragment.name.appending(".rtf"))
      
      #if true // this crashes compiler:
        guard let wrapper = wrapper, let fn = wrapper.filename else { continue }
        // wrappers[fn] = wrapper
      #else // works
        wrappers[wrapper!.filename!] = wrapper
      #endif
    }
    return wrappers
  }