Compiler crash in Swift 5 language mode, when using generic, convenience init, assumeIsolated

[tomlokhorst]

Description

This program crashes the compiler in language mode 5, but works in language mode 6.

Works: swift -swift-version 6 main.swift
Crashes: swift -swift-version 5 main.swift

When removing the generic, the convenience init or the assumeIsolated, it won't crash.

Reproduction

import Foundation

@MainActor
public class Foo<T> {

    public convenience init(t: T) {
        self.init()

        let queue = DispatchQueue.main
        queue.async { [weak self] in
            MainActor.assumeIsolated {
                self?.bar(x: 3)
            }
        }
    }

    func bar(x: Int) {
        print("hello", x)
    }
}

let f = Foo(t: 1)

try await Task.sleep(for: .seconds(1))
print("Done", f)

Stack dump

Stack dump:
0.	Program arguments: /Applications/Xcode-16.2.0.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swift-frontend -frontend -interpret main.swift -Xllvm -aarch64-use-tbi -enable-objc-interop -stack-check -sdk /Applications/Xcode-16.2.0.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX15.2.sdk -color-diagnostics -swift-version 5 -new-driver-path /Applications/Xcode-16.2.0.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swift-driver -empty-abi-descriptor -resource-dir /Applications/Xcode-16.2.0.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/swift -module-name main -disable-clang-spi -target-sdk-version 15.2 -target-sdk-name macosx15.2 -external-plugin-path /Applications/Xcode-16.2.0.app/Contents/Developer/Platforms/MacOSX.platform/Developer/usr/lib/swift/host/plugins#/Applications/Xcode-16.2.0.app/Contents/Developer/Platforms/MacOSX.platform/Developer/usr/bin/swift-plugin-server -external-plugin-path /Applications/Xcode-16.2.0.app/Contents/Developer/Platforms/MacOSX.platform/Developer/usr/local/lib/swift/host/plugins#/Applications/Xcode-16.2.0.app/Contents/Developer/Platforms/MacOSX.platform/Developer/usr/bin/swift-plugin-server -plugin-path /Applications/Xcode-16.2.0.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/lib/swift/host/plugins -plugin-path /Applications/Xcode-16.2.0.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/local/lib/swift/host/plugins
1.	Apple Swift version 6.0.3 (swiftlang-6.0.3.1.10 clang-1600.0.30.1)
2.	Compiling with effective version 5.10
3.	While evaluating request ASTLoweringRequest(Lowering AST to SIL for module main)
4.	While silgen emitValueConstructor SIL function "@$s4main3FooC1tACyxGx_tcfC".
 for 'init(t:)' (at main.swift:6:24)
Stack dump without symbol names (ensure you have llvm-symbolizer in your PATH or set the environment var `LLVM_SYMBOLIZER_PATH` to point to it):
0  swift-frontend           0x000000010a8f2a9c llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) + 56
1  swift-frontend           0x000000010a8f0cf0 llvm::sys::RunSignalHandlers() + 112
2  swift-frontend           0x000000010a8f3068 SignalHandler(int) + 292
3  libsystem_platform.dylib 0x000000019c942e04 _sigtramp + 56
4  swift-frontend           0x0000000106ce3764 swift::InFlightSubstitution::substType(swift::SubstitutableType*, unsigned int) + 48
5  swift-frontend           0x0000000106ce3764 swift::InFlightSubstitution::substType(swift::SubstitutableType*, unsigned int) + 48
6  swift-frontend           0x0000000106ce78d0 std::__1::optional<swift::Type> llvm::function_ref<std::__1::optional<swift::Type> (swift::TypeBase*)>::callback_fn<substType(swift::Type, unsigned int, swift::InFlightSubstitution&)::$_0>(long, swift::TypeBase*) + 868
7  swift-frontend           0x0000000106cc6580 swift::Type::transformWithPosition(swift::TypePosition, llvm::function_ref<std::__1::optional<swift::Type> (swift::TypeBase*, swift::TypePosition)>) const + 92
8  swift-frontend           0x0000000106cc7e3c swift::Type::transformWithPosition(swift::TypePosition, llvm::function_ref<std::__1::optional<swift::Type> (swift::TypeBase*, swift::TypePosition)>) const + 6424
9  swift-frontend           0x0000000106cc6894 swift::Type::transformWithPosition(swift::TypePosition, llvm::function_ref<std::__1::optional<swift::Type> (swift::TypeBase*, swift::TypePosition)>) const + 880
10 swift-frontend           0x0000000106ce3f14 substType(swift::Type, unsigned int, swift::InFlightSubstitution&) + 312
11 swift-frontend           0x0000000106ce36d0 swift::Type::subst(llvm::function_ref<swift::Type (swift::SubstitutableType*)>, llvm::function_ref<swift::ProtocolConformanceRef (swift::CanType, swift::Type, swift::ProtocolDecl*)>, swift::SubstOptions) const + 340
12 swift-frontend           0x0000000105b0ccec getSILFunctionType(swift::Lowering::TypeConverter&, swift::TypeExpansionContext, swift::Lowering::AbstractionPattern, swift::CanTypeWrapper<swift::AnyFunctionType>, swift::SILExtInfoBuilder, (anonymous namespace)::Conventions const&, swift::ForeignInfo const&, std::__1::optional<swift::SILDeclRef>, std::__1::optional<swift::SILDeclRef>, std::__1::optional<swift::SubstitutionMap>, swift::ProtocolConformanceRef) + 5092
13 swift-frontend           0x0000000105b028f0 getNativeSILFunctionType(swift::Lowering::TypeConverter&, swift::TypeExpansionContext, swift::Lowering::AbstractionPattern, swift::CanTypeWrapper<swift::AnyFunctionType>, swift::SILExtInfoBuilder, std::__1::optional<swift::SILDeclRef>, std::__1::optional<swift::SILDeclRef>, std::__1::optional<swift::SubstitutionMap>, swift::ProtocolConformanceRef) + 596
14 swift-frontend           0x0000000105b062fc getUncachedSILFunctionTypeForConstant(swift::Lowering::TypeConverter&, swift::TypeExpansionContext, swift::SILDeclRef, swift::Lowering::TypeConverter::LoweredFormalTypes) + 1352
15 swift-frontend           0x0000000105b06e84 swift::Lowering::TypeConverter::getConstantInfo(swift::TypeExpansionContext, swift::SILDeclRef) + 192
16 swift-frontend           0x0000000105afc644 swift::SILFunctionBuilder::getOrCreateFunction(swift::SILLocation, swift::SILDeclRef, swift::ForDefinition_t, llvm::function_ref<swift::SILFunction* (swift::SILLocation, swift::SILDeclRef)>, swift::ProfileCounter) + 132
17 swift-frontend           0x0000000105cb3c94 swift::Lowering::SILGenModule::getFunction(swift::SILDeclRef, swift::ForDefinition_t) + 440
18 swift-frontend           0x0000000105cbf6a0 void llvm::function_ref<void ()>::callback_fn<swift::Lowering::SILGenModule::emitClosure(swift::AbstractClosureExpr*, swift::Lowering::FunctionTypeInfo const&)::$_0>(long) + 92
19 swift-frontend           0x0000000105cb8810 swift::Lowering::SILGenModule::emitClosure(swift::AbstractClosureExpr*, swift::Lowering::FunctionTypeInfo const&) + 280
20 swift-frontend           0x0000000105d5fb30 (anonymous namespace)::RValueEmitter::visitAbstractClosureExpr(swift::AbstractClosureExpr*, swift::Lowering::SGFContext) + 2948
21 swift-frontend           0x0000000105d4f5d0 (anonymous namespace)::RValueEmitter::visitCaptureListExpr(swift::CaptureListExpr*, swift::Lowering::SGFContext) + 124
22 swift-frontend           0x0000000105d531c0 (anonymous namespace)::RValueEmitter::visitFunctionConversionExpr(swift::FunctionConversionExpr*, swift::Lowering::SGFContext) + 3528
23 swift-frontend           0x0000000105d3b58c swift::Lowering::SILGenFunction::emitRValueAsSingleValue(swift::Expr*, swift::Lowering::SGFContext) + 40
24 swift-frontend           0x0000000105cda068 (anonymous namespace)::ArgEmitter::emit(swift::Lowering::ArgumentSource&&, swift::Lowering::AbstractionPattern, std::__1::optional<swift::AnyFunctionType::Param>) + 5028
25 swift-frontend           0x0000000105cc80f0 (anonymous namespace)::ArgEmitter::emitSingleArg(swift::Lowering::ArgumentSource&&, swift::Lowering::AbstractionPattern, std::__1::optional<swift::AnyFunctionType::Param>) + 216
26 swift-frontend           0x0000000105cd89ac (anonymous namespace)::ArgEmitter::emitPreparedArgs(swift::Lowering::PreparedArguments&&, swift::Lowering::AbstractionPattern) + 256
27 swift-frontend           0x0000000105ce4878 (anonymous namespace)::CallSite::emit(swift::Lowering::SILGenFunction&, swift::Lowering::AbstractionPattern, swift::CanTypeWrapper<swift::SILFunctionType>, (anonymous namespace)::ParamLowering&, llvm::SmallVectorImpl<swift::Lowering::ManagedValue>&, llvm::SmallVectorImpl<(anonymous namespace)::DelayedArgument>&, swift::ForeignInfo const&) && + 664
28 swift-frontend           0x0000000105ce4298 (anonymous namespace)::CallEmission::emitArgumentsForNormalApply(swift::Lowering::AbstractionPattern, swift::CanTypeWrapper<swift::SILFunctionType>, swift::ForeignInfo const&, llvm::SmallVectorImpl<swift::Lowering::ManagedValue>&, std::__1::optional<swift::SILLocation>&) + 1000
29 swift-frontend           0x0000000105ccce7c (anonymous namespace)::CallEmission::apply(swift::Lowering::SGFContext) + 2028
30 swift-frontend           0x0000000105ccb408 swift::Lowering::SILGenFunction::emitApplyExpr(swift::ApplyExpr*, swift::Lowering::SGFContext) + 3116
31 swift-frontend           0x0000000105d3bc74 swift::Lowering::SILGenFunction::emitIgnoredExpr(swift::Expr*) + 888
32 swift-frontend           0x0000000105df3274 swift::ASTVisitor<(anonymous namespace)::StmtEmitter, void, void, void, void, void, void>::visit(swift::Stmt*) + 5512
33 swift-frontend           0x0000000105d0d774 swift::Lowering::SILGenFunction::emitValueConstructor(swift::ConstructorDecl*) + 14032
34 swift-frontend           0x0000000105cb67e4 swift::Lowering::SILGenModule::emitFunctionDefinition(swift::SILDeclRef, swift::SILFunction*) + 7596
35 swift-frontend           0x0000000105cb73bc swift::Lowering::SILGenModule::emitOrDelayFunction(swift::SILDeclRef) + 216
36 swift-frontend           0x0000000105cb8674 swift::Lowering::SILGenModule::emitConstructor(swift::ConstructorDecl*) + 724
37 swift-frontend           0x0000000105e072c0 (anonymous namespace)::SILGenType::emitType() + 564
38 swift-frontend           0x0000000105cb4624 swift::ASTVisitor<swift::Lowering::SILGenModule, void, void, void, void, void, void>::visit(swift::Decl*) + 104
39 swift-frontend           0x0000000105cbb038 swift::ASTLoweringRequest::evaluate(swift::Evaluator&, swift::ASTLoweringDescriptor) const + 1804
40 swift-frontend           0x0000000105df192c 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
41 swift-frontend           0x0000000105cbff14 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
42 swift-frontend           0x000000010529a304 swift::performCompileStepsPostSema(swift::CompilerInstance&, int&, swift::FrontendObserver*) + 2828
43 swift-frontend           0x000000010529d374 performCompile(swift::CompilerInstance&, int&, swift::FrontendObserver*) + 2944
44 swift-frontend           0x000000010529bbb4 swift::performFrontend(llvm::ArrayRef<char const*>, char const*, void*, swift::FrontendObserver*) + 3572
45 swift-frontend           0x0000000105222a5c swift::mainEntry(int, char const**) + 3680
46 dyld                     0x000000019c58c274 start + 2840
Segmentation fault: 11

Expected behavior

I expect the code to compile in language mode 5 as well as 6, it seems like valid code.

Environment

swift-driver version: 1.115.1 Apple Swift version 6.0.3 (swiftlang-6.0.3.1.10 clang-1600.0.30.1)
Target: arm64-apple-macosx15.0

Additional information

No response