Compiler crash on use of "Self" in class.

Stack dump:
0.	Program arguments: /Applications/Xcode-beta.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swift -frontend -c -primary-file /Users/marcinkrzyzanowski/Devel/foobar/foobar-ios-app/foobarClient/Sources/foobarClient/Client.swift /Users/marcinkrzyzanowski/Devel/foobar/foobar-ios-app/foobarClient/Sources/foobarClient/Logging.swift -emit-module-path /Users/marcinkrzyzanowski/Devel/foobar/foobar-ios-app/DerivedData/foobar/Build/Intermediates.noindex/foobarClient.build/Debug-iphonesimulator/foobarClient.build/Objects-normal/x86_64/Client~partial.swiftmodule -emit-module-doc-path /Users/marcinkrzyzanowski/Devel/foobar/foobar-ios-app/DerivedData/foobar/Build/Intermediates.noindex/foobarClient.build/Debug-iphonesimulator/foobarClient.build/Objects-normal/x86_64/Client~partial.swiftdoc -serialize-diagnostics-path /Users/marcinkrzyzanowski/Devel/foobar/foobar-ios-app/DerivedData/foobar/Build/Intermediates.noindex/foobarClient.build/Debug-iphonesimulator/foobarClient.build/Objects-normal/x86_64/Client.dia -emit-dependencies-path /Users/marcinkrzyzanowski/Devel/foobar/foobar-ios-app/DerivedData/foobar/Build/Intermediates.noindex/foobarClient.build/Debug-iphonesimulator/foobarClient.build/Objects-normal/x86_64/Client.d -emit-reference-dependencies-path /Users/marcinkrzyzanowski/Devel/foobar/foobar-ios-app/DerivedData/foobar/Build/Intermediates.noindex/foobarClient.build/Debug-iphonesimulator/foobarClient.build/Objects-normal/x86_64/Client.swiftdeps -target x86_64-apple-ios8.0-simulator -enable-objc-interop -sdk /Applications/Xcode-beta.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator13.0.sdk -I /Users/marcinkrzyzanowski/Devel/foobar/foobar-ios-app/DerivedData/foobar/Build/Products/Debug-iphonesimulator -F /Users/marcinkrzyzanowski/Devel/foobar/foobar-ios-app/DerivedData/foobar/Build/Products/Debug-iphonesimulator -F /Applications/Xcode-beta.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/Library/Frameworks -enable-testing -g -module-cache-path /Users/marcinkrzyzanowski/Devel/foobar/foobar-ios-app/DerivedData/ModuleCache.noindex -swift-version 5 -enforce-exclusivity=checked -Onone -D SWIFT_PACKAGE -D DEBUG -D Xcode -serialize-debugging-options -Xcc -working-directory -Xcc /Users/marcinkrzyzanowski/Devel/foobar/foobar-ios-app/foobarClient -enable-anonymous-context-mangled-names -Xcc -I/Users/marcinkrzyzanowski/Devel/foobar/foobar-ios-app/DerivedData/foobar/Build/Products/Debug-iphonesimulator/include -Xcc -I/Users/marcinkrzyzanowski/Devel/foobar/foobar-ios-app/DerivedData/foobar/Build/Intermediates.noindex/foobarClient.build/Debug-iphonesimulator/foobarClient.build/DerivedSources-normal/x86_64 -Xcc -I/Users/marcinkrzyzanowski/Devel/foobar/foobar-ios-app/DerivedData/foobar/Build/Intermediates.noindex/foobarClient.build/Debug-iphonesimulator/foobarClient.build/DerivedSources/x86_64 -Xcc -I/Users/marcinkrzyzanowski/Devel/foobar/foobar-ios-app/DerivedData/foobar/Build/Intermediates.noindex/foobarClient.build/Debug-iphonesimulator/foobarClient.build/DerivedSources -Xcc -DDEBUG=1 -module-name foobarClient -o /Users/marcinkrzyzanowski/Devel/foobar/foobar-ios-app/DerivedData/foobar/Build/Intermediates.noindex/foobarClient.build/Debug-iphonesimulator/foobarClient.build/Objects-normal/x86_64/Client.o -index-store-path /Users/marcinkrzyzanowski/Devel/foobar/foobar-ios-app/DerivedData/foobar/Index/DataStore -index-system-modules 
1.	While silgen emitStoredPropertyInitialization SIL function "@$s13foobarClient10RESTClientC6client33_0EBAB9A809F32F447F87F938DAB26558LL9KituraKitAFCvpfi".
 for expression at [/Users/marcinkrzyzanowski/Devel/foobar/foobar-ios-app/foobarClient/Sources/foobarClient/Client.swift:13:24 - line:13:58] RangeText="KituraKit(baseURL: Self.urlString)"
0  swift                    0x0000000111019963 PrintStackTraceSignalHandler(void*) + 51
1  swift                    0x0000000111019136 SignalHandler(int) + 358
2  libsystem_platform.dylib 0x00007fff7d49eb5d _sigtramp + 29
3  libsystem_platform.dylib 0x0000000000000001 _sigtramp + 2192970945
4  swift                    0x000000010d58c868 swift::MetatypeInst::create(swift::SILDebugLocation, swift::SILType, swift::SILFunction*, swift::SILOpenedArchetypesState&) + 72
5  swift                    0x000000010d03e104 swift::SILBuilder::createMetatype(swift::SILLocation, swift::SILType) + 148
6  swift                    0x000000010d0b0e9b swift::Lowering::SILGenBuilder::createMetatype(swift::SILLocation, swift::SILType) + 187
7  swift                    0x000000010d0e344c swift::ASTVisitor<(anonymous namespace)::RValueEmitter, swift::Lowering::RValue, void, void, void, void, void, swift::Lowering::SGFContext>::visit(swift::Expr*, swift::Lowering::SGFContext) + 17964
8  swift                    0x000000010d0df3dc swift::ASTVisitor<(anonymous namespace)::RValueEmitter, swift::Lowering::RValue, void, void, void, void, void, swift::Lowering::SGFContext>::visit(swift::Expr*, swift::Lowering::SGFContext) + 1468
9  swift                    0x000000010d123c0f SILGenLValue::visitRec(swift::Expr*, swift::Lowering::SGFAccessKind, swift::Lowering::LValueOptions, swift::Lowering::AbstractionPattern) + 1279
10 swift                    0x000000010d122c3d swift::ASTVisitor<SILGenLValue, swift::Lowering::LValue, void, void, void, void, void, swift::Lowering::SGFAccessKind, swift::Lowering::LValueOptions>::visit(swift::Expr*, swift::Lowering::SGFAccessKind, swift::Lowering::LValueOptions) + 10685
11 swift                    0x000000010d1201a2 swift::Lowering::SILGenFunction::emitLValue(swift::Expr*, swift::Lowering::SGFAccessKind, swift::Lowering::LValueOptions) + 34
12 swift                    0x000000010d0e5ea9 swift::ASTVisitor<(anonymous namespace)::RValueEmitter, swift::Lowering::RValue, void, void, void, void, void, swift::Lowering::SGFContext>::visit(swift::Expr*, swift::Lowering::SGFContext) + 28809
13 swift                    0x000000010d0814db (anonymous namespace)::ArgEmitter::emit(swift::Lowering::ArgumentSource&&, swift::Lowering::AbstractionPattern) + 4475
14 swift                    0x000000010d085052 (anonymous namespace)::ArgEmitter::emitExpanded(swift::Lowering::ArgumentSource&&, swift::Lowering::AbstractionPattern) + 306
15 swift                    0x000000010d0937df (anonymous namespace)::ArgEmitter::emitTopLevel(swift::Lowering::ArgumentSource&&, swift::Lowering::AbstractionPattern) + 5887
16 swift                    0x000000010d091e8d (anonymous namespace)::CallSite::emit(swift::Lowering::SILGenFunction&, swift::Lowering::AbstractionPattern, swift::CanTypeWrapper<swift::SILFunctionType>, (anonymous namespace)::ParamLowering&, llvm::SmallVectorImpl<swift::Lowering::ManagedValue>&, llvm::SmallVectorImpl<(anonymous namespace)::DelayedArgument>&, llvm::Optional<swift::ForeignErrorConvention> const&, swift::ImportAsMemberStatus) && + 701
17 swift                    0x000000010d08f00b (anonymous namespace)::CallEmission::emitArgumentsForNormalApply(swift::CanTypeWrapper<swift::FunctionType>&, swift::Lowering::AbstractionPattern&, swift::CanTypeWrapper<swift::SILFunctionType>, llvm::Optional<swift::ForeignErrorConvention> const&, swift::ImportAsMemberStatus, llvm::SmallVectorImpl<swift::Lowering::ManagedValue>&, llvm::Optional<swift::SILLocation>&, swift::CanTypeWrapper<swift::FunctionType>&) + 1451
18 swift                    0x000000010d08cac3 (anonymous namespace)::CallEmission::apply(swift::Lowering::SGFContext) + 3059
19 swift                    0x000000010d088dab swift::Lowering::SILGenFunction::emitApplyExpr(swift::Expr*, swift::Lowering::SGFContext) + 2331
20 swift                    0x000000010d0f30e9 (anonymous namespace)::RValueEmitter::emitForceValue(swift::ForceValueExpr*, swift::Expr*, unsigned int, swift::Lowering::SGFContext) + 1817
21 swift                    0x000000010d159b47 swift::Lowering::SILGenFunction::emitReturnExpr(swift::SILLocation, swift::Expr*) + 439
22 swift                    0x000000010d10c615 swift::Lowering::SILGenFunction::emitGeneratorFunction(swift::SILDeclRef, swift::Expr*) + 581
23 swift                    0x000000010d077b95 swift::Lowering::SILGenModule::emitStoredPropertyInitialization(swift::PatternBindingDecl*, unsigned int)::$_6::operator()(swift::SILFunction*) const + 245
24 swift                    0x000000010d077858 swift::Lowering::SILGenModule::emitStoredPropertyInitialization(swift::PatternBindingDecl*, unsigned int) + 1000
25 swift                    0x000000010d16342b (anonymous namespace)::SILGenType::emitType() + 1115
26 swift                    0x000000010d07b8ed swift::ASTVisitor<swift::Lowering::SILGenModule, void, void, void, void, void, void>::visit(swift::Decl*) + 77
27 swift                    0x000000010d07ab36 swift::Lowering::SILGenModule::emitSourceFile(swift::SourceFile*) + 1238
28 swift                    0x000000010d07c5bc swift::SILModule::constructSIL(swift::ModuleDecl*, swift::SILOptions&, swift::FileUnit*) + 1244
29 swift                    0x000000010cc869f5 performCompile(swift::CompilerInstance&, swift::CompilerInvocation&, llvm::ArrayRef<char const*>, int&, swift::FrontendObserver*, swift::UnifiedStatsReporter*) + 28757
30 swift                    0x000000010cc7c0a4 swift::performFrontend(llvm::ArrayRef<char const*>, char const*, void*, swift::FrontendObserver*) + 6868
31 swift                    0x000000010cc0b333 main + 1219
32 libdyld.dylib            0x00007fff7d2b33d5 start + 1
error: Segmentation fault: 11