Compiler crash when declaring async function in an extension of a generic ObjC class that uses the generic parameter as a return type

[TadeasKriz]

Description

Declaring an async function in an extension of a generic Objective-C class, results in a compiler crash with the following stack-trace when the generic parameter is used as a return type of the function.

Stack dump:
0.	Program arguments: /Applications/Xcode-14.2.0.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swift-frontend -frontend -c /Users/tadeaskriz/Developer/Sandbox/FoundationBug/KotlinIsh/A_sealed.swift /Users/tadeaskriz/Developer/Sandbox/FoundationBug/KotlinIsh/A_A_sealed.swift -emit-module-path /Users/tadeaskriz/Library/Developer/Xcode/DerivedData/FoundationBug-bwyaiwmgiyrjdshkyygmdyykykjr/Build/Intermediates.noindex/FoundationBug.build/Release/KotlinIsh.build/Objects-normal/arm64/KotlinIsh.swiftmodule -emit-module-doc-path /Users/tadeaskriz/Library/Developer/Xcode/DerivedData/FoundationBug-bwyaiwmgiyrjdshkyygmdyykykjr/Build/Intermediates.noindex/FoundationBug.build/Release/KotlinIsh.build/Objects-normal/arm64/KotlinIsh.swiftdoc -emit-module-source-info-path /Users/tadeaskriz/Library/Developer/Xcode/DerivedData/FoundationBug-bwyaiwmgiyrjdshkyygmdyykykjr/Build/Intermediates.noindex/FoundationBug.build/Release/KotlinIsh.build/Objects-normal/arm64/KotlinIsh.swiftsourceinfo -emit-dependencies-path /Users/tadeaskriz/Library/Developer/Xcode/DerivedData/FoundationBug-bwyaiwmgiyrjdshkyygmdyykykjr/Build/Intermediates.noindex/FoundationBug.build/Release/KotlinIsh.build/Objects-normal/arm64/KotlinIsh-master.d -serialize-diagnostics-path /Users/tadeaskriz/Library/Developer/Xcode/DerivedData/FoundationBug-bwyaiwmgiyrjdshkyygmdyykykjr/Build/Intermediates.noindex/FoundationBug.build/Release/KotlinIsh.build/Objects-normal/arm64/KotlinIsh-master.dia -emit-objc-header-path /Users/tadeaskriz/Library/Developer/Xcode/DerivedData/FoundationBug-bwyaiwmgiyrjdshkyygmdyykykjr/Build/Intermediates.noindex/FoundationBug.build/Release/KotlinIsh.build/Objects-normal/arm64/KotlinIsh-Swift.h -emit-abi-descriptor-path /Users/tadeaskriz/Library/Developer/Xcode/DerivedData/FoundationBug-bwyaiwmgiyrjdshkyygmdyykykjr/Build/Intermediates.noindex/FoundationBug.build/Release/KotlinIsh.build/Objects-normal/arm64/KotlinIsh.abi.json -emit-localized-strings -emit-localized-strings-path /Users/tadeaskriz/Library/Developer/Xcode/DerivedData/FoundationBug-bwyaiwmgiyrjdshkyygmdyykykjr/Build/Intermediates.noindex/FoundationBug.build/Release/KotlinIsh.build/Objects-normal/arm64 -target arm64-apple-macos12.3 -Xllvm -aarch64-use-tbi -enable-objc-interop -stack-check -sdk /Applications/Xcode-14.2.0.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX13.1.sdk -I /Users/tadeaskriz/Library/Developer/Xcode/DerivedData/FoundationBug-bwyaiwmgiyrjdshkyygmdyykykjr/Build/Products/Release -F /Users/tadeaskriz/Library/Developer/Xcode/DerivedData/FoundationBug-bwyaiwmgiyrjdshkyygmdyykykjr/Build/Products/Release -no-color-diagnostics -g -import-underlying-module -module-cache-path /Users/tadeaskriz/Library/Developer/Xcode/DerivedData/ModuleCache.noindex -swift-version 5 -enforce-exclusivity=checked -O -serialize-debugging-options -enable-bare-slash-regex -empty-abi-descriptor -Xcc -working-directory -Xcc /Users/tadeaskriz/Developer/Sandbox/FoundationBug -resource-dir /Applications/Xcode-14.2.0.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/swift -Xcc -I/Users/tadeaskriz/Library/Developer/Xcode/DerivedData/FoundationBug-bwyaiwmgiyrjdshkyygmdyykykjr/Build/Intermediates.noindex/FoundationBug.build/Release/KotlinIsh.build/swift-overrides.hmap -Xcc -iquote -Xcc /Users/tadeaskriz/Library/Developer/Xcode/DerivedData/FoundationBug-bwyaiwmgiyrjdshkyygmdyykykjr/Build/Intermediates.noindex/FoundationBug.build/Release/KotlinIsh.build/KotlinIsh-generated-files.hmap -Xcc -I/Users/tadeaskriz/Library/Developer/Xcode/DerivedData/FoundationBug-bwyaiwmgiyrjdshkyygmdyykykjr/Build/Intermediates.noindex/FoundationBug.build/Release/KotlinIsh.build/KotlinIsh-own-target-headers.hmap -Xcc -I/Users/tadeaskriz/Library/Developer/Xcode/DerivedData/FoundationBug-bwyaiwmgiyrjdshkyygmdyykykjr/Build/Intermediates.noindex/FoundationBug.build/Release/KotlinIsh.build/KotlinIsh-all-non-framework-target-headers.hmap -Xcc -ivfsoverlay -Xcc /Users/tadeaskriz/Library/Developer/Xcode/DerivedData/FoundationBug-bwyaiwmgiyrjdshkyygmdyykykjr/Build/Intermediates.noindex/FoundationBug.build/Release/KotlinIsh.build/all-product-headers.yaml -Xcc -iquote -Xcc /Users/tadeaskriz/Library/Developer/Xcode/DerivedData/FoundationBug-bwyaiwmgiyrjdshkyygmdyykykjr/Build/Intermediates.noindex/FoundationBug.build/Release/KotlinIsh.build/KotlinIsh-project-headers.hmap -Xcc -I/Users/tadeaskriz/Library/Developer/Xcode/DerivedData/FoundationBug-bwyaiwmgiyrjdshkyygmdyykykjr/Build/Products/Release/include -Xcc -I/Users/tadeaskriz/Library/Developer/Xcode/DerivedData/FoundationBug-bwyaiwmgiyrjdshkyygmdyykykjr/Build/Intermediates.noindex/FoundationBug.build/Release/KotlinIsh.build/DerivedSources-normal/arm64 -Xcc -I/Users/tadeaskriz/Library/Developer/Xcode/DerivedData/FoundationBug-bwyaiwmgiyrjdshkyygmdyykykjr/Build/Intermediates.noindex/FoundationBug.build/Release/KotlinIsh.build/DerivedSources/arm64 -Xcc -I/Users/tadeaskriz/Library/Developer/Xcode/DerivedData/FoundationBug-bwyaiwmgiyrjdshkyygmdyykykjr/Build/Intermediates.noindex/FoundationBug.build/Release/KotlinIsh.build/DerivedSources -Xcc -ivfsoverlay -Xcc /Users/tadeaskriz/Library/Developer/Xcode/DerivedData/FoundationBug-bwyaiwmgiyrjdshkyygmdyykykjr/Build/Intermediates.noindex/FoundationBug.build/Release/KotlinIsh.build/unextended-module-overlay.yaml -module-name KotlinIsh -frontend-parseable-output -disable-clang-spi -target-sdk-version 13.1 -num-threads 10 -o /Users/tadeaskriz/Library/Developer/Xcode/DerivedData/FoundationBug-bwyaiwmgiyrjdshkyygmdyykykjr/Build/Intermediates.noindex/FoundationBug.build/Release/KotlinIsh.build/Objects-normal/arm64/A_sealed.o -o /Users/tadeaskriz/Library/Developer/Xcode/DerivedData/FoundationBug-bwyaiwmgiyrjdshkyygmdyykykjr/Build/Intermediates.noindex/FoundationBug.build/Release/KotlinIsh.build/Objects-normal/arm64/A_A_sealed.o -index-unit-output-path /FoundationBug.build/Release/KotlinIsh.build/Objects-normal/arm64/A_sealed.o -index-unit-output-path /FoundationBug.build/Release/KotlinIsh.build/Objects-normal/arm64/A_A_sealed.o
1.	Apple Swift version 5.7.2 (swiftlang-5.7.2.135.5 clang-1400.0.29.51)
2.	Compiling with the current language version
3.	While evaluating request ASTLoweringRequest(Lowering AST to SIL for module KotlinIsh)
4.	While silgen emitNativeToForeignThunk SIL function "@$sSo11GenericTestC9KotlinIshE10asyncCrash1axyp_tYaFTo".
 for 'asyncCrash(a:)' (at /Users/tadeaskriz/Developer/Sandbox/FoundationBug/KotlinIsh/A_sealed.swift:14:5)
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           0x0000000104dab5b0 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) + 56
1  swift-frontend           0x0000000104daa5b4 llvm::sys::RunSignalHandlers() + 112
2  swift-frontend           0x0000000104dabc34 SignalHandler(int) + 344
3  libsystem_platform.dylib 0x00000001af5432a4 _sigtramp + 56
4  swift-frontend           0x000000010053f808 (anonymous namespace)::TypeClassifierBase<(anonymous namespace)::LowerType, swift::Lowering::TypeLowering*>::visitAbstractTypeParamType(swift::CanType, swift::Lowering::AbstractionPattern, swift::Lowering::IsTypeExpansionSensitive_t) + 124
5  swift-frontend           0x000000010053f808 (anonymous namespace)::TypeClassifierBase<(anonymous namespace)::LowerType, swift::Lowering::TypeLowering*>::visitAbstractTypeParamType(swift::CanType, swift::Lowering::AbstractionPattern, swift::Lowering::IsTypeExpansionSensitive_t) + 124
6  swift-frontend           0x00000001005353dc swift::CanTypeVisitor<(anonymous namespace)::LowerType, swift::Lowering::TypeLowering*, swift::Lowering::AbstractionPattern, swift::Lowering::IsTypeExpansionSensitive_t>::visit(swift::CanType, swift::Lowering::AbstractionPattern, swift::Lowering::IsTypeExpansionSensitive_t) + 248
7  swift-frontend           0x0000000100535f0c swift::Lowering::TypeConverter::getTypeLoweringForLoweredType(swift::Lowering::AbstractionPattern, swift::CanType, swift::TypeExpansionContext, swift::Lowering::IsTypeExpansionSensitive_t) + 388
8  swift-frontend           0x0000000100a1734c swift::Lowering::SILGenFunction::emitManagedRValueWithCleanup(swift::SILValue) + 156
9  swift-frontend           0x00000001009e28fc swift::Lowering::SILGenFunction::emitNativeToForeignThunk(swift::SILDeclRef)::$_3::operator()(swift::SILValue) const + 128
10 swift-frontend           0x00000001009e1550 swift::Lowering::SILGenFunction::emitNativeToForeignThunk(swift::SILDeclRef) + 6820
11 swift-frontend           0x00000001009ad204 swift::Lowering::SILGenModule::emitFunctionDefinition(swift::SILDeclRef, swift::SILFunction*) + 2600
12 swift-frontend           0x0000000100a935a4 SILGenExtension::visitFuncDecl(swift::FuncDecl*) + 488
13 swift-frontend           0x0000000100a8f44c SILGenExtension::emitExtension(swift::ExtensionDecl*) + 164
14 swift-frontend           0x00000001009b5b10 swift::ASTVisitor<swift::Lowering::SILGenModule, void, void, void, void, void, void>::visit(swift::Decl*) + 1176
15 swift-frontend           0x00000001009b3ee4 swift::ASTLoweringRequest::evaluate(swift::Evaluator&, swift::ASTLoweringDescriptor) const + 3356
16 swift-frontend           0x0000000100a80f10 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&) + 216
17 swift-frontend           0x00000001009b76e4 llvm::Expected<swift::ASTLoweringRequest::OutputType> swift::Evaluator::getResultUncached<swift::ASTLoweringRequest>(swift::ASTLoweringRequest const&) + 628
18 swift-frontend           0x00000001003f8c9c swift::performFrontend(llvm::ArrayRef<char const*>, char const*, void*, swift::FrontendObserver*) + 7208
19 swift-frontend           0x0000000100399294 swift::mainEntry(int, char const**) + 3940
20 dyld                     0x00000001af1ebe50 start + 2544

Steps to reproduce

@interface GenericTest<T>: NSObject
@end

extension GenericTest {
  @objc
  func asyncCrash() async -> T {
    fatalError()
  }
}

Expected behavior

Code compiles successfully similar to:

• regular sync function with the same signature compiles
• async function returning a specific type instead of the T parameter compiles
• async function that's also throws returning T also compiles

Or if it's not possible to compile, then it should report an error instead of the crash.

Environment

• Swift compiler version info swift-driver version: 1.62.15 Apple Swift version 5.7.2 (swiftlang-5.7.2.135.5 clang-1400.0.29.51)
• Xcode version info Xcode 14.2 Build version 14C18
• Deployment target: macOS 12.3

---

NOTE: The "similar to" points only work when building in release mode (more specifically just setting the Optimization Level to -O is enough). I'll be submitting a separate issue report for a compiler crash that happens when the Optimization Level is set to -Onone and the type parameter is used anywhere in the function signature (except when used as a generic argument of a different class that's used in the signature instead).