Generic segmentation fault

GenericSegmentationFault.swift

// TestType - constrained to built-in protocol, uses conditional conformance (a)

struct TestType<T: Error> { }

// Conditional conformance (b)
extension Array: Error where Element: Error { }

struct GenericType<G> {
    // FAILS: These both segmentation fault (c)
        func test<T>(_ value: TestType<[T]>) { }
    //    static func test<T>(_ value: TestType<[T]>) { }

    // FAILS: It doesn't help to ensure the compiler that T is Error, which it knows means that [T] also is
    //        func test<T>(_ value: TestType<[T]>) where T: Error { }

    // But if TestType<[T]> is in the return type, it works (d)
    func test<T>() -> TestType<[T]> { fatalError() }

    // This is also ok, without the array, so it's related to conditional conformance (b)
    func test<T>(_ value: TestType<T>) { }

    // Also fine, where we use the generic parameter of the type (c)
    func test(_ value: TestType<[G]>) where G: Error { }
}

struct NonGEnericType {
    // And this, where the only difference is that the outer type is no longer generic (c)
    func test<T>(_ value: TestType<[T]>) { }
}

// PestType - constrained to our own protocol, uses conditional conformance (a)

protocol Terror { }

struct PestType<T: Terror> { }

extension Array: Terror where Element: Terror { }

// This works, using PestType which is completely analogous to TestType,
// except that its constraint is to a homemade protocol
struct Pest<G> {
    func test<T>(_ value: PestType<[T]>) { }
}

/* So the following are needed to cause the segfault:

 - Using a built-in protocol (a)
 - Conditional conformance (with the conditional protocol either the same or different) (b)
 - The test type must be generic, with a different parameter than the test function (c)
 - The conditionally conformed type must be an input parameter, not return (d)

 (b)
 // Conditional conformance - this also segfaults
 extension Array: Error where Element: RawRepresentable { }

 // Without conditional conformance - but this works
 extension Array: Error { }
 */

/*
 1.    Apple Swift version 5.5 (swiftlang-1300.0.27.6 clang-1300.0.27.2)
 2.
 3.    While evaluating request IRGenRequest(IR Generation for file "Bug.swift")
 4.    While emitting IR SIL function "@$s7asfsadf4TestV4testyyAA9RawValuedVySayqd__GAGSYAAqd__SYHD1__HCg_GSYRd__lF".
 for 'test(_:)' (at Bug.swift:53:5)
 5.    While mangling type for debugger type 'RawValued<Array<T>>' (declared at [Bug.swift:12:1 - line:12:41] RangeText="struct RawValued<T: RawRepresentable> { ")
 Stack dump without symbol names (ensure you have llvm-symbolizer in your PATH or set the environment var `LLVM_SYMBOLIZER_PATH` to point to it):
 0  swift-frontend           0x000000010868cd18 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) + 56
 1  swift-frontend           0x000000010868be20 llvm::sys::RunSignalHandlers() + 128
 2  swift-frontend           0x000000010868d358 SignalHandler(int) + 292
 3  libsystem_platform.dylib 0x00000001a0912c44 _sigtramp + 56
 4  swift-frontend           0x000000010542a5ac swift::GenericSignatureImpl::getConformanceAccessPath(swift::Type, swift::ProtocolDecl*) const + 68
 5  swift-frontend           0x00000001052dbb08 swift::Mangle::ASTMangler::appendAnyProtocolConformance(swift::CanGenericSignature, swift::CanType, swift::ProtocolConformanceRef) + 64
 6  swift-frontend           0x00000001052d9728 swift::Mangle::ASTMangler::appendConcreteProtocolConformance(swift::ProtocolConformance const*) + 1688
 7  swift-frontend           0x00000001052d80f4 swift::Mangle::ASTMangler::appendRetroactiveConformances(swift::SubstitutionMap, swift::ModuleDecl*) + 184
 8  swift-frontend           0x00000001052d7b94 swift::Mangle::ASTMangler::appendRetroactiveConformances(swift::Type) + 468
 9  swift-frontend           0x00000001052d07f0 swift::Mangle::ASTMangler::appendType(swift::Type, swift::ValueDecl const*) + 2836
 10 swift-frontend           0x00000001052d51fc swift::Mangle::ASTMangler::mangleTypeForDebugger(swift::Type, swift::GenericSignature) + 540
 11 swift-frontend           0x000000010486fda0 (anonymous namespace)::IRGenDebugInfoImpl::getOrCreateType(swift::irgen::DebugTypeInfo) + 1304
 12 swift-frontend           0x000000010486ba20 (anonymous namespace)::IRGenDebugInfoImpl::emitVariableDeclaration(swift::irgen::IRBuilder&, llvm::ArrayRef<llvm::Value*>, swift::irgen::DebugTypeInfo, swift::SILDebugScope const*, swift::ValueDecl*, swift::SILDebugVariable, swift::irgen::IndirectionKind, swift::irgen::ArtificialKind) + 560
 13 swift-frontend           0x000000010489c134 swift::SILInstructionVisitor<(anonymous namespace)::IRGenSILFunction, void>::visit(swift::SILInstruction*) + 70916
 14 swift-frontend           0x00000001048861bc swift::irgen::IRGenModule::emitSILFunction(swift::SILFunction*) + 7732
 15 swift-frontend           0x0000000104760a08 swift::irgen::IRGenerator::emitGlobalTopLevel(std::__1::vector<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >, std::__1::allocator<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > > > const&) + 1332
 16 swift-frontend           0x000000010485a19c swift::IRGenRequest::evaluate(swift::Evaluator&, swift::IRGenDescriptor) const + 7572
 17 swift-frontend           0x00000001048840b0 swift::SimpleRequest<swift::IRGenRequest, swift::GeneratedModule (swift::IRGenDescriptor), (swift::RequestFlags)9>::evaluateRequest(swift::IRGenRequest const&, swift::Evaluator&) + 188
 18 swift-frontend           0x0000000104864618 llvm::Expected<swift::IRGenRequest::OutputType> swift::Evaluator::getResultUncached<swift::IRGenRequest>(swift::IRGenRequest const&) + 752
 19 swift-frontend           0x000000010485de3c swift::performIRGeneration(swift::FileUnit*, swift::IRGenOptions const&, swift::TBDGenOptions const&, std::__1::unique_ptr<swift::SILModule, std::__1::default_delete<swift::SILModule> >, llvm::StringRef, swift::PrimarySpecificPaths const&, llvm::StringRef, llvm::GlobalVariable**) + 236
 20 swift-frontend           0x0000000104428f20 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*) + 2540
 21 swift-frontend           0x000000010441c1dc swift::performFrontend(llvm::ArrayRef<char const*>, char const*, void*, swift::FrontendObserver*) + 6428
 22 swift-frontend           0x0000000104376bc0 main + 932
 23 libdyld.dylib            0x00000001a08e5450 start + 4
 error: Segmentation fault: 11 (in target 'asfsadf' from project 'asfsadf')
 */