Assertion failed: (!type->hasArchetype() && "already have a contextual type"), function mapTypeIntoContext, file /Users/swiftninjas/s4tf/swift/lib/AST/GenericEnvironment.cpp, line 116.
Stack dump:
0.  Program arguments: /Library/Developer/Toolchains/swift-DEVELOPMENT-SNAPSHOT-2019-09-30-a.xctoolchain/usr/bin/swift -frontend -c -primary-file sr-11563.sil -target x86_64-apple-darwin18.7.0 -enable-objc-interop -sdk /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.15.sdk -color-diagnostics -module-name main -o /var/folders/m_/6f7q8zfs3n9fr0c_4gy8840m00hc_q/T/sr-11563-1ac3d6.o
1.  Swift version 5.1-dev (LLVM 200186e28b, Swift 1238976565)
2.  While emitting IR SIL function "@$s4main3FooVyxGSQAASQRzlSQ2eeoiySbx_xtFZTW".
 for sr-11563.sil:55:43
0  swift                    0x00000001111f8715 llvm::sys::PrintStackTrace(llvm::raw_ostream&) + 37
1  swift                    0x00000001111f7a05 llvm::sys::RunSignalHandlers() + 85
2  swift                    0x00000001111f8cf8 SignalHandler(int) + 264
3  libsystem_platform.dylib 0x00007fff6f4d0b5d _sigtramp + 29
4  libsystem_platform.dylib 0x0000000127288938 _sigtramp + 3084615160
5  libsystem_c.dylib        0x00007fff6f38a6a6 abort + 127
6  libsystem_c.dylib        0x00007fff6f35320d basename_r + 0
7  swift                    0x0000000111672a41 swift::GenericEnvironment::mapTypeIntoContext(swift::GenericEnvironment*, swift::Type) (.cold.1) + 33
8  swift                    0x000000010e6a2c84 swift::GenericEnvironment::mapTypeIntoContext(swift::GenericEnvironment*, swift::Type) + 68
9  swift                    0x000000010d99d700 swift::CanType llvm::function_ref<swift::CanType (swift::CanType)>::callback_fn<(anonymous namespace)::EmitPolymorphicParameters::bindExtraSource(swift::irgen::MetadataSource const&, swift::irgen::Explosion&, swift::irgen::WitnessMetadata*)::$_12>(long, swift::CanType) + 16
10 swift                    0x000000010da2ae39 bool llvm::function_ref<bool (unsigned int, swift::CanType, swift::ProtocolDecl*)>::callback_fn<swift::irgen::IRGenFunction::bindLocalTypeDataFromSelfWitnessTable(swift::ProtocolConformance const*, llvm::Value*, llvm::function_ref<swift::CanType (swift::CanType)>)::$_0>(long, unsigned int, swift::CanType, swift::ProtocolDecl*) + 41
11 swift                    0x000000010e17826d swift::SILWitnessTable::enumerateWitnessTableConditionalConformances(swift::ProtocolConformance const*, llvm::function_ref<bool (unsigned int, swift::CanType, swift::ProtocolDecl*)>) + 221
12 swift                    0x000000010da28f8e swift::irgen::IRGenFunction::bindLocalTypeDataFromSelfWitnessTable(swift::ProtocolConformance const*, llvm::Value*, llvm::function_ref<swift::CanType (swift::CanType)>) + 62
13 swift                    0x000000010d997b82 swift::irgen::emitPolymorphicParameters(swift::irgen::IRGenFunction&, swift::SILFunction&, swift::irgen::Explosion&, swift::irgen::WitnessMetadata*, llvm::function_ref<llvm::Value* (unsigned int)> const&) + 754
14 swift                    0x000000010d9f38d0 swift::irgen::IRGenModule::emitSILFunction(swift::SILFunction*) + 6016
15 swift                    0x000000010d9115cb swift::irgen::IRGenerator::emitLazyDefinitions() + 1243
16 swift                    0x000000010d9cec55 performIRGeneration(swift::IRGenOptions&, swift::ModuleDecl*, std::__1::unique_ptr<swift::SILModule, std::__1::default_delete<swift::SILModule> >, llvm::StringRef, swift::PrimarySpecificPaths const&, llvm::LLVMContext&, swift::SourceFile*, llvm::GlobalVariable**) + 1477
17 swift                    0x000000010d9cd460 swift::performIRGeneration(swift::IRGenOptions&, swift::ModuleDecl*, std::__1::unique_ptr<swift::SILModule, std::__1::default_delete<swift::SILModule> >, llvm::StringRef, swift::PrimarySpecificPaths const&, llvm::LLVMContext&, llvm::ArrayRef<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > >, llvm::GlobalVariable**) + 960
18 swift                    0x000000010d87b821 performCompile(swift::CompilerInstance&, swift::CompilerInvocation&, llvm::ArrayRef<char const*>, int&, swift::FrontendObserver*, swift::UnifiedStatsReporter*) + 13233
19 swift                    0x000000010d877540 swift::performFrontend(llvm::ArrayRef<char const*>, char const*, void*, swift::FrontendObserver*) + 3024