Swift compiler segfaults on generic Collection - swift

Question

I was trying to create a generic collection, PowerCollection, such that e.g. PowerCollection([0,1], 2) would contain [0, 0], [0, 1], [1, 0], and [1, 1], but I ran into trouble. Even with all method implementations stubbed out, the compiler is segfaulting and I don't know why.
Here is a minimal example that causes the segfault. Am I doing something wrong here?
I am using: Xcode 12.3 (17715) (Build 12C33) on macOS Version 10.15.7 (Build 19H2)
struct PowerCollection<C : Collection> : Collection {
typealias Index = [C.Index]
typealias Element = [C.Element]
var startIndex, endIndex: Index
subscript(position: Index) -> [C.Element] {
return []
}
func index(after i: Index) -> Index {
return i
}
}
extension Array : Comparable where Element : Comparable {
public static func < (lhs: [Element], rhs: [Element]) -> Bool {
return false
}
}
Trying to compile the above gave me a compiler segfault with the following stack dump
0. Program arguments: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swift -frontend -c -primary-file /Users/justinh/Desktop/CrashInvestigation/CrashInvestigation/main.swift -emit-module-path /Users/justinh/Library/Developer/Xcode/DerivedData/CrashInvestigation-hgzhbvtdchhupjellxarahpklfll/Build/Intermediates.noindex/CrashInvestigation.build/Debug/CrashInvestigation.build/Objects-normal/x86_64/main~partial.swiftmodule -emit-module-doc-path /Users/justinh/Library/Developer/Xcode/DerivedData/CrashInvestigation-hgzhbvtdchhupjellxarahpklfll/Build/Intermediates.noindex/CrashInvestigation.build/Debug/CrashInvestigation.build/Objects-normal/x86_64/main~partial.swiftdoc -emit-module-source-info-path /Users/justinh/Library/Developer/Xcode/DerivedData/CrashInvestigation-hgzhbvtdchhupjellxarahpklfll/Build/Intermediates.noindex/CrashInvestigation.build/Debug/CrashInvestigation.build/Objects-normal/x86_64/main~partial.swiftsourceinfo -serialize-diagnostics-path /Users/justinh/Library/Developer/Xcode/DerivedData/CrashInvestigation-hgzhbvtdchhupjellxarahpklfll/Build/Intermediates.noindex/CrashInvestigation.build/Debug/CrashInvestigation.build/Objects-normal/x86_64/main.dia -emit-dependencies-path /Users/justinh/Library/Developer/Xcode/DerivedData/CrashInvestigation-hgzhbvtdchhupjellxarahpklfll/Build/Intermediates.noindex/CrashInvestigation.build/Debug/CrashInvestigation.build/Objects-normal/x86_64/main.d -emit-reference-dependencies-path /Users/justinh/Library/Developer/Xcode/DerivedData/CrashInvestigation-hgzhbvtdchhupjellxarahpklfll/Build/Intermediates.noindex/CrashInvestigation.build/Debug/CrashInvestigation.build/Objects-normal/x86_64/main.swiftdeps -target x86_64-apple-macos11.0 -enable-objc-interop -sdk /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX11.1.sdk -I /Users/justinh/Library/Developer/Xcode/DerivedData/CrashInvestigation-hgzhbvtdchhupjellxarahpklfll/Build/Products/Debug -F /Users/justinh/Library/Developer/Xcode/DerivedData/CrashInvestigation-hgzhbvtdchhupjellxarahpklfll/Build/Products/Debug -enable-testing -g -module-cache-path /Users/justinh/Library/Developer/Xcode/DerivedData/ModuleCache.noindex -swift-version 5 -enforce-exclusivity=checked -Onone -D DEBUG -serialize-debugging-options -Xcc -working-directory -Xcc /Users/justinh/Desktop/CrashInvestigation -enable-anonymous-context-mangled-names -Xcc -I/Users/justinh/Library/Developer/Xcode/DerivedData/CrashInvestigation-hgzhbvtdchhupjellxarahpklfll/Build/Intermediates.noindex/CrashInvestigation.build/Debug/CrashInvestigation.build/swift-overrides.hmap -Xcc -iquote -Xcc /Users/justinh/Library/Developer/Xcode/DerivedData/CrashInvestigation-hgzhbvtdchhupjellxarahpklfll/Build/Intermediates.noindex/CrashInvestigation.build/Debug/CrashInvestigation.build/CrashInvestigation-generated-files.hmap -Xcc -I/Users/justinh/Library/Developer/Xcode/DerivedData/CrashInvestigation-hgzhbvtdchhupjellxarahpklfll/Build/Intermediates.noindex/CrashInvestigation.build/Debug/CrashInvestigation.build/CrashInvestigation-own-target-headers.hmap -Xcc -I/Users/justinh/Library/Developer/Xcode/DerivedData/CrashInvestigation-hgzhbvtdchhupjellxarahpklfll/Build/Intermediates.noindex/CrashInvestigation.build/Debug/CrashInvestigation.build/CrashInvestigation-all-target-headers.hmap -Xcc -iquote -Xcc /Users/justinh/Library/Developer/Xcode/DerivedData/CrashInvestigation-hgzhbvtdchhupjellxarahpklfll/Build/Intermediates.noindex/CrashInvestigation.build/Debug/CrashInvestigation.build/CrashInvestigation-project-headers.hmap -Xcc -I/Users/justinh/Library/Developer/Xcode/DerivedData/CrashInvestigation-hgzhbvtdchhupjellxarahpklfll/Build/Products/Debug/include -Xcc -I/Users/justinh/Library/Developer/Xcode/DerivedData/CrashInvestigation-hgzhbvtdchhupjellxarahpklfll/Build/Intermediates.noindex/CrashInvestigation.build/Debug/CrashInvestigation.build/DerivedSources-normal/x86_64 -Xcc -I/Users/justinh/Library/Developer/Xcode/DerivedData/CrashInvestigation-hgzhbvtdchhupjellxarahpklfll/Build/Intermediates.noindex/CrashInvestigation.build/Debug/CrashInvestigation.build/DerivedSources/x86_64 -Xcc -I/Users/justinh/Library/Developer/Xcode/DerivedData/CrashInvestigation-hgzhbvtdchhupjellxarahpklfll/Build/Intermediates.noindex/CrashInvestigation.build/Debug/CrashInvestigation.build/DerivedSources -Xcc -DDEBUG=1 -target-sdk-version 11.1 -module-name CrashInvestigation -o /Users/justinh/Library/Developer/Xcode/DerivedData/CrashInvestigation-hgzhbvtdchhupjellxarahpklfll/Build/Intermediates.noindex/CrashInvestigation.build/Debug/CrashInvestigation.build/Objects-normal/x86_64/main.o -index-store-path /Users/justinh/Library/Developer/Xcode/DerivedData/CrashInvestigation-hgzhbvtdchhupjellxarahpklfll/Index/DataStore -index-system-modules
1. Apple Swift version 5.3.2 (swiftlang-1200.0.45 clang-1200.0.32.28)
2. While evaluating request IRGenSourceFileRequest(IR Generation for file "/Users/justinh/Desktop/CrashInvestigation/CrashInvestigation/main.swift")
3. While emitting IR SIL function "#$s18CrashInvestigation15PowerCollectionVyxGSlAASl20_failEarlyRangeCheck_6boundsySny5IndexQzG_AItFTW".
for '_failEarlyRangeCheck(_:bounds:)' (in module 'Swift')
4. While mangling type for debugger type 'Range<Array<τ_0_0.Index>>'
0 swift 0x000000011288f615 llvm::sys::PrintStackTrace(llvm::raw_ostream&) + 37
1 swift 0x000000011288e615 llvm::sys::RunSignalHandlers() + 85
2 swift 0x000000011288fbcf SignalHandler(int) + 111
3 libsystem_platform.dylib 0x00007fff6fddd5fd _sigtramp + 29
4 libsystem_platform.dylib 0x00007faafe8397c0 _sigtramp + 18446743711030559200
5 swift 0x000000010f69e03f swift::GenericSignatureImpl::getConformanceAccessPath(swift::Type, swift::ProtocolDecl*) + 31
6 swift 0x000000010f598069 swift::Mangle::ASTMangler::appendAnyProtocolConformance(swift::CanGenericSignature, swift::CanType, swift::ProtocolConformanceRef) + 217
7 swift 0x000000010f596386 swift::Mangle::ASTMangler::appendConcreteProtocolConformance(swift::ProtocolConformance const*) + 2070
8 swift 0x000000010f594aa3 swift::Mangle::ASTMangler::appendRetroactiveConformances(swift::SubstitutionMap, swift::ModuleDecl*) + 179
9 swift 0x000000010f58de5e swift::Mangle::ASTMangler::appendType(swift::Type, swift::ValueDecl const*) + 3454
10 swift 0x000000010f591af8 swift::Mangle::ASTMangler::mangleTypeForDebugger(swift::Type, swift::DeclContext const*) + 632
11 swift 0x000000010e7c9d21 (anonymous namespace)::IRGenDebugInfoImpl::getOrCreateType(swift::irgen::DebugTypeInfo) + 1505
12 swift 0x000000010e7cb8e5 (anonymous namespace)::IRGenDebugInfoImpl::createParameterTypes(swift::CanTypeWrapper<swift::SILFunctionType>) + 1461
13 swift 0x000000010e7c2af4 (anonymous namespace)::IRGenDebugInfoImpl::emitFunction(swift::SILDebugScope const*, llvm::Function*, swift::SILFunctionTypeRepresentation, swift::SILType, swift::DeclContext*) + 2868
14 swift 0x000000010e7e245f swift::irgen::IRGenModule::emitSILFunction(swift::SILFunction*) + 2639
15 swift 0x000000010e67d3a7 swift::irgen::IRGenerator::emitLazyDefinitions() + 1207
16 swift 0x000000010e7b8d20 performIRGeneration(swift::IRGenOptions const&, swift::ModuleDecl*, std::__1::unique_ptr<swift::SILModule, std::__1::default_delete<swift::SILModule> >, llvm::StringRef, swift::PrimarySpecificPaths const&, llvm::StringRef, swift::SourceFile*, llvm::GlobalVariable**, llvm::StringSet<llvm::MallocAllocator>*) + 1920
17 swift 0x000000010e7e1781 swift::SimpleRequest<swift::IRGenSourceFileRequest, swift::GeneratedModule (swift::IRGenDescriptor), (swift::RequestFlags)9>::evaluateRequest(swift::IRGenSourceFileRequest const&, swift::Evaluator&) + 97
18 swift 0x000000010e7bd04c llvm::Expected<swift::IRGenSourceFileRequest::OutputType> swift::Evaluator::getResultUncached<swift::IRGenSourceFileRequest>(swift::IRGenSourceFileRequest const&) + 940
19 swift 0x000000010e7b929d swift::performIRGeneration(swift::IRGenOptions const&, swift::SourceFile&, std::__1::unique_ptr<swift::SILModule, std::__1::default_delete<swift::SILModule> >, llvm::StringRef, swift::PrimarySpecificPaths const&, llvm::StringRef, llvm::GlobalVariable**, llvm::StringSet<llvm::MallocAllocator>*) + 269
20 swift 0x000000010e4031ba performCompileStepsPostSILGen(swift::CompilerInstance&, swift::CompilerInvocation const&, std::__1::unique_ptr<swift::SILModule, std::__1::default_delete<swift::SILModule> >, llvm::PointerUnion<swift::ModuleDecl*, swift::SourceFile*>, swift::PrimarySpecificPaths const&, int&, swift::FrontendObserver*) + 3002
21 swift 0x000000010e3f2d97 swift::performFrontend(llvm::ArrayRef<char const*>, char const*, void*, swift::FrontendObserver*) + 20695
22 swift 0x000000010e373c27 main + 1255
23 libdyld.dylib 0x00007fff6fbe4cc9 start + 1
24 libdyld.dylib 0x000000000000004b start + 18446603338641421187
error: Segmentation fault: 11 (in target 'CrashInvestigation' from project 'CrashInvestigation')