Compiler crash with strict concurrency and referring to another @MainActor class

[lyamamot]

Description

The code snippet has a class that constructs another class, which constructs another class in its initializer. These are all classes annotated with @MainActor.

Changing things about the last object in the chain can prevent the crash.

Reproduction

This crashes with swiftc -strict-concurrency=complete

// Removing @MainActor here prevents the crash.
@MainActor
class AnotherModel {
    // Commenting this next line also prevents the crash.
    init() {}
}

@MainActor
class AppViewModel {
    init(anotherModel: AnotherModel = AnotherModel()) {}
}

@MainActor
struct AppView {
    private var model = AppViewModel()
}

Stack dump

1.	Apple Swift version 5.10 (swiftlang-5.10.0.13 clang-1500.3.9.4)
2.	Compiling with the current language version
3.	While evaluating request IRGenRequest(IR Generation for file "Crashy.swift")
4.	While emitting IR SIL function "@$s6Crashy7AppViewV5model33_DCA0530D12908CEF73E9453845BB263DLLAA0bC5ModelCvpfi".
 for expression at [Crashy.swift:15:25 - line:15:38] RangeText="AppViewModel("
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           0x0000000105d07f3c llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) + 56
1  swift-frontend           0x0000000105d070f8 llvm::sys::RunSignalHandlers() + 112
2  swift-frontend           0x0000000105d08544 SignalHandler(int) + 360
3  libsystem_platform.dylib 0x000000018844da24 _sigtramp + 56
4  swift-frontend           0x000000010069879c llvm::IRBuilderBase::CreateAlignedLoad(llvm::Type*, llvm::Value*, llvm::MaybeAlign, bool, llvm::Twine const&) + 88
5  swift-frontend           0x000000010069879c llvm::IRBuilderBase::CreateAlignedLoad(llvm::Type*, llvm::Value*, llvm::MaybeAlign, bool, llvm::Twine const&) + 88
6  swift-frontend           0x00000001009f1704 swift::irgen::IRGenFunction::emitSuspensionPoint(swift::irgen::Explosion&, llvm::Value*) + 984
7  swift-frontend           0x0000000100b3a9a8 (anonymous namespace)::IRGenSILFunction::visitSILBasicBlock(swift::SILBasicBlock*) + 68520
8  swift-frontend           0x0000000100b284fc swift::irgen::IRGenModule::emitSILFunction(swift::SILFunction*) + 11556
9  swift-frontend           0x000000010097c430 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&) + 2472
10 swift-frontend           0x0000000100adb940 swift::IRGenRequest::evaluate(swift::Evaluator&, swift::IRGenDescriptor) const + 4016
11 swift-frontend           0x0000000100b2554c swift::SimpleRequest<swift::IRGenRequest, swift::GeneratedModule (swift::IRGenDescriptor), (swift::RequestFlags)9>::evaluateRequest(swift::IRGenRequest const&, swift::Evaluator&) + 176
12 swift-frontend           0x0000000100ae8264 llvm::Expected<swift::IRGenRequest::OutputType> swift::Evaluator::getResultUncached<swift::IRGenRequest>(swift::IRGenRequest const&) + 836
13 swift-frontend           0x0000000100ade438 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**) + 264
14 swift-frontend           0x000000010060c0b8 generateIR(swift::IRGenOptions const&, swift::TBDGenOptions const&, std::__1::unique_ptr<swift::SILModule, std::__1::default_delete<swift::SILModule>>, swift::PrimarySpecificPaths const&, llvm::StringRef, llvm::PointerUnion<swift::ModuleDecl*, swift::SourceFile*>, llvm::GlobalVariable*&, llvm::ArrayRef<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char>>>) + 156
15 swift-frontend           0x0000000100606294 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*) + 1892
16 swift-frontend           0x0000000100605444 swift::performCompileStepsPostSema(swift::CompilerInstance&, int&, swift::FrontendObserver*) + 608
17 swift-frontend           0x0000000100609694 performCompile(swift::CompilerInstance&, int&, swift::FrontendObserver*) + 1448
18 swift-frontend           0x00000001006076d0 swift::performFrontend(llvm::ArrayRef<char const*>, char const*, void*, swift::FrontendObserver*) + 4968
19 swift-frontend           0x0000000100596e8c swift::mainEntry(int, char const**) + 2612
20 dyld                     0x000000018809d0e0 start + 2360
error: fatalError

Expected behavior

It should not crash. The code looks reasonable to me.

Environment

swift-driver version: 1.90.11.1 Apple Swift version 5.10 (swiftlang-5.10.0.13 clang-1500.3.9.4)
Target: arm64-apple-macosx14.0

Additional information

Without -strict-concurrency=complete, the compiler reports an error:

crash.swift:10:39: error: call to main actor-isolated initializer 'init()' in a synchronous nonisolated context
    init(anotherModel: AnotherModel = AnotherModel()) {}
                                      ^
crash.swift:5:5: note: calls to initializer 'init()' from outside of its actor context are implicitly asynchronous
    init() {}
    ^
error: fatalError