Compiler crash when accessing keyPath on protocol with associated type

[finnvoor]

Description
When a protocol has an associatedtype, accessing a value of the associatedtype crashes the compiler if accessed by keypath, but not when accessed directly.

Straightforward reproduction:

// CompileTest.swift

protocol MyProtocol {
    associatedtype MyAssociatedType
    
    var value: MyAssociatedType { get }
}

var instance: (any MyProtocol)!

_ = instance[keyPath: \.value] // 💥 error: compile command failed due to signal 5

_ = instance.value // ✅

Output of swiftc CompileTest.swift:

error: compile command failed due to signal 5 (use -v to see invocation)
[cleanup]   %12 = project_box %11 : $<τ_0_0 where τ_0_0 : MyProtocol> { var τ_0_0.MyAssociatedType } <@opened("3A03861C-6F4D-11EE-968A-EEA571DF391E", any MyProtocol) Self>, 0 // user: %13
Please submit a bug report (https://swift.org/contributing/#reporting-bugs) and include the crash backtrace.
Stack dump:
0.	Program arguments: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swift-frontend -frontend -c -primary-file CompileTest.swift -target arm64-apple-macosx14.0 -Xllvm -aarch64-use-tbi -enable-objc-interop -stack-check -sdk /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX14.0.sdk -color-diagnostics -new-driver-path /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swift-driver -empty-abi-descriptor -resource-dir /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/swift -module-name CompileTest -disable-clang-spi -target-sdk-version 14.0 -target-sdk-name macosx14.0 -external-plugin-path /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX14.0.sdk/usr/lib/swift/host/plugins#/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX14.0.sdk/usr/bin/swift-plugin-server -external-plugin-path /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX14.0.sdk/usr/local/lib/swift/host/plugins#/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX14.0.sdk/usr/bin/swift-plugin-server -external-plugin-path /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/usr/lib/swift/host/plugins#/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/usr/bin/swift-plugin-server -external-plugin-path /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/usr/local/lib/swift/host/plugins#/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/usr/bin/swift-plugin-server -plugin-path /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/swift/host/plugins -plugin-path /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/local/lib/swift/host/plugins -o /var/folders/qm/mxhmrhdj3fv3ntq8b9f_tgl80000gn/T/TemporaryDirectory.jcV5Bm/CompileTest-1.o
1.	Apple Swift version 5.9 (swiftlang-5.9.2.1.6 clang-1500.1.0.1.1)
2.	Compiling with the current language version
3.	While evaluating request ASTLoweringRequest(Lowering AST to SIL for file "CompileTest.swift")
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           0x0000000106126038 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) + 56
1  swift-frontend           0x000000010a3bd688 llvm::sys::RunSignalHandlers() + 112
2  swift-frontend           0x000000010a3be6f4 SignalHandler(int) + 352
3  libsystem_platform.dylib 0x000000018805da24 _sigtramp + 56
4  swift-frontend           0x0000000108276c60 (anonymous namespace)::Transform::transform(swift::Lowering::ManagedValue, swift::Lowering::AbstractionPattern, swift::CanType, swift::Lowering::AbstractionPattern, swift::CanType, swift::SILType, swift::Lowering::SGFContext) (.llvm.6659257712363558512) + 6988
5  swift-frontend           0x000000010649e624 getOrCreateKeyPathGetter(swift::Lowering::SILGenModule&, swift::AbstractStorageDecl*, swift::SubstitutionMap, swift::GenericEnvironment*, swift::ResilienceExpansion, llvm::ArrayRef<std::__1::pair<swift::CanType, swift::SILType>>, swift::CanType, swift::CanType) + 4000
6  swift-frontend           0x0000000107eb4b44 swift::Lowering::SILGenModule::emitKeyPathComponentForDecl(swift::SILLocation, swift::GenericEnvironment*, swift::ResilienceExpansion, unsigned int&, bool&, swift::SubstitutionMap, swift::AbstractStorageDecl*, llvm::ArrayRef<swift::ProtocolConformanceRef>, swift::CanType, swift::DeclContext*, bool) + 1652
7  swift-frontend           0x000000010589b2ec (anonymous namespace)::RValueEmitter::visitKeyPathExpr(swift::KeyPathExpr*, swift::Lowering::SGFContext) + 1156
8  swift-frontend           0x000000010586c170 swift::Lowering::SILGenFunction::emitRValueAsSingleValue(swift::Expr*, swift::Lowering::SGFContext) + 40
9  swift-frontend           0x000000010804aa20 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) + 3348
10 swift-frontend           0x000000010661a5e8 swift::Lowering::SILGenFunction::emitLValue(swift::Expr*, swift::Lowering::SGFAccessKind, swift::Lowering::LValueOptions) + 48
11 swift-frontend           0x0000000107f29b58 (anonymous namespace)::RValueEmitter::visitKeyPathApplicationExpr(swift::KeyPathApplicationExpr*, swift::Lowering::SGFContext) + 120
12 swift-frontend           0x0000000107eb34a0 swift::Lowering::SILGenFunction::emitIgnoredExpr(swift::Expr*) + 892
13 swift-frontend           0x0000000107f59ea4 (anonymous namespace)::RValueEmitter::visitAssignExpr(swift::AssignExpr*, swift::Lowering::SGFContext) + 568
14 swift-frontend           0x0000000107eb34a0 swift::Lowering::SILGenFunction::emitIgnoredExpr(swift::Expr*) + 892
15 swift-frontend           0x0000000107c346d0 swift::ASTVisitor<swift::Lowering::SILGenModule, void, void, void, void, void, void>::visit(swift::Decl*) + 664
16 swift-frontend           0x0000000107c4c888 swift::ASTLoweringRequest::evaluate(swift::Evaluator&, swift::ASTLoweringDescriptor) const + 2908
17 swift-frontend           0x000000010836b76c swift::SimpleRequest<swift::ASTLoweringRequest, std::__1::unique_ptr<swift::SILModule, std::__1::default_delete<swift::SILModule>> (swift::ASTLoweringDescriptor), (swift::RequestFlags)9>::evaluateRequest(swift::ASTLoweringRequest const&, swift::Evaluator&) + 200
18 swift-frontend           0x0000000107c93358 llvm::Expected<swift::ASTLoweringRequest::OutputType> swift::Evaluator::getResultUncached<swift::ASTLoweringRequest>(swift::ASTLoweringRequest const&) + 584
19 swift-frontend           0x000000010a3744dc performCompile(swift::CompilerInstance&, int&, swift::FrontendObserver*) + 1680
20 swift-frontend           0x000000010a377c2c swift::performFrontend(llvm::ArrayRef<char const*>, char const*, void*, swift::FrontendObserver*) + 4568
21 swift-frontend           0x0000000109cea058 swift::mainEntry(int, char const**) + 4116
22 dyld                     0x0000000187cb5058 start + 2224

Environment

swift-driver version: 1.87.2 Apple Swift version 5.9 (swiftlang-5.9.2.1.6 clang-1500.1.0.1.1)
Target: arm64-apple-macosx14.0