Compiler crash when adding async initializer to actor protocol

[davedelong]

Description

Adding an async initializer in an extension on an Actor-constrained protocol crashes the compiler. Removing the : Actor constraint on the protocol makes the issue go away. Removing async from the initializer makes the issue go away.

Reproduction

struct Schema { }

protocol Engine: Actor {
	init(schema: Schema) async
}

extension Engine {
	init() async { await self.init(schema: .init()) }
}

Stack dump

0.	Program arguments: /Applications/Xcode16.2.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swift-frontend -frontend -interpret crash.swift -Xllvm -aarch64-use-tbi -enable-objc-interop -stack-check -sdk /Applications/Xcode16.2.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX15.2.sdk -color-diagnostics -new-driver-path /Applications/Xcode16.2.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swift-driver -empty-abi-descriptor -resource-dir /Applications/Xcode16.2.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/swift -module-name crash -disable-clang-spi -target-sdk-version 15.2 -target-sdk-name macosx15.2 -external-plugin-path /Applications/Xcode16.2.app/Contents/Developer/Platforms/MacOSX.platform/Developer/usr/lib/swift/host/plugins#/Applications/Xcode16.2.app/Contents/Developer/Platforms/MacOSX.platform/Developer/usr/bin/swift-plugin-server -external-plugin-path /Applications/Xcode16.2.app/Contents/Developer/Platforms/MacOSX.platform/Developer/usr/local/lib/swift/host/plugins#/Applications/Xcode16.2.app/Contents/Developer/Platforms/MacOSX.platform/Developer/usr/bin/swift-plugin-server -plugin-path /Applications/Xcode16.2.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/swift/host/plugins -plugin-path /Applications/Xcode16.2.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/local/lib/swift/host/plugins
1.	Apple Swift version 6.0.3 (swiftlang-6.0.3.1.9 clang-1600.0.30.1)
2.	Compiling with effective version 5.10
3.	While evaluating request ASTLoweringRequest(Lowering AST to SIL for module crash)
4.	While silgen emitValueConstructor SIL function "@$s5crash6EnginePAAExyYacfC".
 for 'init()' (at crash.swift:8:2)
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           0x0000000106312aac llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) + 56
1  swift-frontend           0x0000000106310d00 llvm::sys::RunSignalHandlers() + 112
2  swift-frontend           0x0000000106313078 SignalHandler(int) + 292
3  libsystem_platform.dylib 0x000000018d63ade4 _sigtramp + 56
4  libsystem_pthread.dylib  0x000000018d603f70 pthread_kill + 288
5  libsystem_c.dylib        0x000000018d510908 abort + 128
6  swift-frontend           0x0000000100c45970 swift::Diagnostic::operator=(swift::Diagnostic const&) + 0
7  swift-frontend           0x00000001017287ac swift::Lowering::SILGenFunction::emitMainExecutor(swift::SILLocation) + 0
8  swift-frontend           0x00000001017284bc swift::Lowering::SILGenFunction::emitConstructorPrologActorHop(swift::SILLocation, std::__1::optional<swift::ActorIsolation>) + 84
9  swift-frontend           0x000000010172a984 swift::Lowering::SILGenFunction::emitValueConstructor(swift::ConstructorDecl*) + 2256
10 swift-frontend           0x00000001016d67f4 swift::Lowering::SILGenModule::emitFunctionDefinition(swift::SILDeclRef, swift::SILFunction*) + 7596
11 swift-frontend           0x00000001016d73cc swift::Lowering::SILGenModule::emitOrDelayFunction(swift::SILDeclRef) + 216
12 swift-frontend           0x00000001016d8684 swift::Lowering::SILGenModule::emitConstructor(swift::ConstructorDecl*) + 724
13 swift-frontend           0x000000010182bb04 swift::ASTVisitor<SILGenExtension, void, void, void, void, void, void>::visit(swift::Decl*) + 372
14 swift-frontend           0x00000001018280f8 SILGenExtension::emitExtension(swift::ExtensionDecl*) + 424
15 swift-frontend           0x00000001016d46d4 swift::ASTVisitor<swift::Lowering::SILGenModule, void, void, void, void, void, void>::visit(swift::Decl*) + 264
16 swift-frontend           0x00000001016db048 swift::ASTLoweringRequest::evaluate(swift::Evaluator&, swift::ASTLoweringDescriptor) const + 1804
17 swift-frontend           0x000000010181193c 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&) + 196
18 swift-frontend           0x00000001016dff24 swift::ASTLoweringRequest::OutputType swift::Evaluator::getResultUncached<swift::ASTLoweringRequest, swift::ASTLoweringRequest::OutputType swift::evaluateOrFatal<swift::ASTLoweringRequest>(swift::Evaluator&, swift::ASTLoweringRequest)::'lambda'()>(swift::ASTLoweringRequest const&, swift::ASTLoweringRequest::OutputType swift::evaluateOrFatal<swift::ASTLoweringRequest>(swift::Evaluator&, swift::ASTLoweringRequest)::'lambda'()) + 528
19 swift-frontend           0x0000000100cba314 swift::performCompileStepsPostSema(swift::CompilerInstance&, int&, swift::FrontendObserver*) + 2828
20 swift-frontend           0x0000000100cbd384 performCompile(swift::CompilerInstance&, int&, swift::FrontendObserver*) + 2944
21 swift-frontend           0x0000000100cbbbc4 swift::performFrontend(llvm::ArrayRef<char const*>, char const*, void*, swift::FrontendObserver*) + 3572
22 swift-frontend           0x0000000100c42a6c swift::mainEntry(int, char const**) + 3680
23 dyld                     0x000000018d284274 start + 2840

Expected behavior

I would expect this to compile correctly.

Environment

% swiftc --version
swift-driver version: 1.115.1 Apple Swift version 6.0.3 (swiftlang-6.0.3.1.9 clang-1600.0.30.1)
Target: arm64-apple-macosx15.0

(Xcode 16.2 on macOS 15.3.2)

Additional information

No response

[davedelong]

This crashes in Xcode 16.2, but does not appear to crash with Xcode 16.3, and does crash with the Swift nightly build:

/tmp % /Applications/Xcode16.2.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swift crash.swift
Stack dump:
...
zsh: abort       crash.swift
/tmp % /Applications/Xcode16.3RC2.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swift crash.swift
/tmp %

Nightly output: https://godbolt.org/z/PK7EE7hfs

[CodaFi]

Fails on ToT +Asserts

Assertion failed: (isCtorWithHopsInjectedByDefiniteInit()), function emitConstructorExpectedExecutorProlog, file SILGenConcurrency.cpp, line 273.
Please submit a bug report (https://swift.org/contributing/#reporting-bugs) and include the crash backtrace.
Stack dump:
0.	Program arguments: ./build/Ninja-DebugAssert/swift-macosx-arm64/bin/swift-frontend -emit-ir /Users/rwidmann/test.swift
1.	Swift version 6.2-dev (LLVM da17cd8368b0838, Swift 65a515b2d4539be)
2.	Compiling with effective version 5.10
3.	While evaluating request ASTLoweringRequest(Lowering AST to SIL for module test)
4.	While silgen emitValueConstructor SIL function "@$s4test6EnginePAAExyYacfC".
 for 'init()' (at /Users/rwidmann/test.swift:8:2)
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           0x000000010f7cd100 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) + 88
1  swift-frontend           0x000000010f7cd644 PrintStackTraceSignalHandler(void*) + 28
2  swift-frontend           0x000000010f7cb608 llvm::sys::RunSignalHandlers() + 152
3  swift-frontend           0x000000010f7ce3c0 SignalHandler(int, __siginfo*, void*) + 284
4  libsystem_platform.dylib 0x000000019b09ade4 _sigtramp + 56
5  libsystem_pthread.dylib  0x000000019b063f70 pthread_kill + 288
6  libsystem_c.dylib        0x000000019af70908 abort + 128
7  libsystem_c.dylib        0x000000019af6fc1c err + 0
8  swift-frontend           0x00000001016414f8 swift::Lowering::SILGenFunction::emitConstructorExpectedExecutorProlog() + 288
9  swift-frontend           0x0000000101647200 swift::Lowering::SILGenFunction::emitValueConstructor(swift::ConstructorDecl*) + 884
10 swift-frontend           0x0000000101594f04 swift::Lowering::SILGenModule::emitFunctionDefinition(swift::SILDeclRef, swift::SILFunction*) + 3916
11 swift-frontend           0x00000001015976ec swift::Lowering::SILGenModule::emitOrDelayFunction(swift::SILDeclRef) + 456
12 swift-frontend           0x0000000101598f5c swift::Lowering::SILGenModule::emitConstructor(swift::ConstructorDecl*) + 476
13 swift-frontend           0x000000010182c4a8 SILGenExtension::visitConstructorDecl(swift::ConstructorDecl*) + 40
14 swift-frontend           0x000000010182bd9c swift::ASTVisitor<SILGenExtension, void, void, void, void, void, void>::visit(swift::Decl*) + 836
15 swift-frontend           0x000000010182ba24 SILGenExtension::visit(swift::Decl*) + 64
16 swift-frontend           0x000000010181b274 SILGenExtension::emitExtension(swift::ExtensionDecl*) + 232
17 swift-frontend           0x000000010181b14c swift::Lowering::SILGenModule::visitExtensionDecl(swift::ExtensionDecl*) + 48
18 swift-frontend           0x0000000101593c2c swift::ASTVisitor<swift::Lowering::SILGenModule, void, void, void, void, void, void>::visit(swift::Decl*) + 1244
19 swift-frontend           0x0000000101593740 swift::Lowering::SILGenModule::visit(swift::Decl*) + 60
20 swift-frontend           0x000000010159bbbc swift::Lowering::SILGenModule::emitSourceFile(swift::SourceFile*) + 256
21 swift-frontend           0x000000010159c564 swift::ASTLoweringRequest::evaluate(swift::Evaluator&, swift::ASTLoweringDescriptor) const + 728
22 swift-frontend           0x00000001017f4234 std::__1::unique_ptr<swift::SILModule, std::__1::default_delete<swift::SILModule>> swift::SimpleRequest<swift::ASTLoweringRequest, std::__1::unique_ptr<swift::SILModule, std::__1::default_delete<swift::SILModule>> (swift::ASTLoweringDescriptor), (swift::RequestFlags)17>::callDerived<0ul>(swift::Evaluator&, std::__1::integer_sequence<unsigned long, 0ul>) const + 116
23 swift-frontend           0x00000001017f4180 swift::SimpleRequest<swift::ASTLoweringRequest, std::__1::unique_ptr<swift::SILModule, std::__1::default_delete<swift::SILModule>> (swift::ASTLoweringDescriptor), (swift::RequestFlags)17>::evaluateRequest(swift::ASTLoweringRequest const&, swift::Evaluator&) + 40
24 swift-frontend           0x00000001015bbcc8 swift::ASTLoweringRequest::OutputType swift::Evaluator::getResultUncached<swift::ASTLoweringRequest, swift::ASTLoweringRequest::OutputType swift::evaluateOrFatal<swift::ASTLoweringRequest>(swift::Evaluator&, swift::ASTLoweringRequest)::'lambda'()>(swift::ASTLoweringRequest const&, swift::ASTLoweringRequest::OutputType swift::evaluateOrFatal<swift::ASTLoweringRequest>(swift::Evaluator&, swift::ASTLoweringRequest)::'lambda'()) + 248
25 swift-frontend           0x00000001015bbbc4 swift::ASTLoweringRequest::OutputType swift::Evaluator::operator()<swift::ASTLoweringRequest, swift::ASTLoweringRequest::OutputType swift::evaluateOrFatal<swift::ASTLoweringRequest>(swift::Evaluator&, swift::ASTLoweringRequest)::'lambda'(), (void*)0>(swift::ASTLoweringRequest const&, swift::ASTLoweringRequest::OutputType swift::evaluateOrFatal<swift::ASTLoweringRequest>(swift::Evaluator&, swift::ASTLoweringRequest)::'lambda'()) + 40
26 swift-frontend           0x000000010159cce8 swift::ASTLoweringRequest::OutputType swift::evaluateOrFatal<swift::ASTLoweringRequest>(swift::Evaluator&, swift::ASTLoweringRequest) + 40
27 swift-frontend           0x000000010159cc08 swift::performASTLowering(swift::ModuleDecl*, swift::Lowering::TypeConverter&, swift::SILOptions const&, swift::IRGenOptions const*) + 184
28 swift-frontend           0x000000010049fdc4 swift::performCompileStepsPostSema(swift::CompilerInstance&, int&, swift::FrontendObserver*) + 240
29 swift-frontend           0x00000001004c36c0 performAction(swift::CompilerInstance&, int&, swift::FrontendObserver*)::$_7::operator()(swift::CompilerInstance&) const + 140
30 swift-frontend           0x00000001004c3624 bool llvm::function_ref<bool (swift::CompilerInstance&)>::callback_fn<performAction(swift::CompilerInstance&, int&, swift::FrontendObserver*)::$_7>(long, swift::CompilerInstance&) + 32
31 swift-frontend           0x00000001004c2a48 llvm::function_ref<bool (swift::CompilerInstance&)>::operator()(swift::CompilerInstance&) const + 40
32 swift-frontend           0x00000001004c15e4 withSemanticAnalysis(swift::CompilerInstance&, swift::FrontendObserver*, llvm::function_ref<bool (swift::CompilerInstance&)>, bool) + 452
33 swift-frontend           0x00000001004bb8fc performAction(swift::CompilerInstance&, int&, swift::FrontendObserver*) + 1284
34 swift-frontend           0x00000001004a22a8 performCompile(swift::CompilerInstance&, int&, swift::FrontendObserver*) + 256
35 swift-frontend           0x00000001004a16b0 swift::performFrontend(llvm::ArrayRef<char const*>, char const*, void*, swift::FrontendObserver*) + 1896
36 swift-frontend           0x00000001000feb48 run_driver(llvm::StringRef, llvm::ArrayRef<char const*>, llvm::ArrayRef<char const*>) + 1720
37 swift-frontend           0x00000001000fd9e8 swift::mainEntry(int, char const**) + 1160
38 swift-frontend           0x00000001000fd16c main + 36
39 dyld                     0x000000019ace4274 start + 2840
fish: Job 1, './build/Ninja-DebugAssert/swift…' terminated by signal SIGABRT (Abort)