Compiler crash when capturing optional isolated parameter in a closure

[Jnosh]

Description

The following snippet crashes the compiler with recent Swift 6.0 development snapshot toolchains.

Did not crash: swift-6.0-DEVELOPMENT-SNAPSHOT-2024-04-18-a
Does crash: swift-6.0-DEVELOPMENT-SNAPSHOT-2024-04-20-a and newer

The StrictConcurrency upcoming feature must be enabled for the crash to occur and I can only reproduce the crash when compiling via swift-frontend (as done by Xcode) not when invoking swiftc.

To reproduce, compile the snippet as follows:
<path to toolchain>/usr/bin/swift-frontend -frontend -c -enable-upcoming-feature StrictConcurrency Crash.swift

Reproduction

func f(f: () -> Void) {}

func main(isolation: isolated (any Actor)?) {
    f { isolation }
}

Stack dump

Assertion failed: ((!actorInstance || (actorIsolation.getKind() == ActorIsolation::ActorInstance && actorInstance->getType().isAnyActor())) && "actorInstance must be an actor if it is non-empty"), function SILIsolationInfo, file PartitionUtils.h, line 134.
Please submit a bug report (https://swift.org/contributing/#reporting-bugs) and include the crash backtrace.
Stack dump:
0.	Program arguments: /Users/<user>/Library/Developer/Toolchains/swift-6.0-DEVELOPMENT-SNAPSHOT-2024-04-22-a.xctoolchain/usr/bin/swift-frontend -frontend -c -enable-upcoming-feature StrictConcurrency Crash.swift
1.	Apple Swift version 6.0-dev (LLVM 94447cf359772fc, Swift f36098a14a0d48b)
2.	Compiling with effective version 5.10
3.	While evaluating request ExecuteSILPipelineRequest(Run pipelines { Mandatory Diagnostic Passes + Enabling Optimization Passes } on SIL for Crash)
4.	While running pass #52 SILFunctionTransform "TransferNonSendable" on SILFunction "@$s5Crash4main9isolationyScA_pSgYi_tF".
 for 'main(isolation:)' (at Crash.swift:3:1)
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           0x00000001097c8adc llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) + 56
1  swift-frontend           0x00000001097c72a8 llvm::sys::RunSignalHandlers() + 112
2  swift-frontend           0x00000001097c9124 SignalHandler(int) + 304
3  libsystem_platform.dylib 0x000000019b1ef584 _sigtramp + 56
4  libsystem_pthread.dylib  0x000000019b1bec20 pthread_kill + 288
5  libsystem_c.dylib        0x000000019b0cba20 abort + 180
6  libsystem_c.dylib        0x000000019b0cad10 err + 0
7  swift-frontend           0x000000010992d38c llvm::DenseMapBase<llvm::DenseMap<swift::SILFunction*, std::__1::unique_ptr<swift::RegionAnalysisFunctionInfo, std::__1::default_delete<swift::RegionAnalysisFunctionInfo>>, llvm::DenseMapInfo<swift::SILFunction*, void>, llvm::detail::DenseMapPair<swift::SILFunction*, std::__1::unique_ptr<swift::RegionAnalysisFunctionInfo, std::__1::default_delete<swift::RegionAnalysisFunctionInfo>>>>, swift::SILFunction*, std::__1::unique_ptr<swift::RegionAnalysisFunctionInfo, std::__1::default_delete<swift::RegionAnalysisFunctionInfo>>, llvm::DenseMapInfo<swift::SILFunction*, void>, llvm::detail::DenseMapPair<swift::SILFunction*, std::__1::unique_ptr<swift::RegionAnalysisFunctionInfo, std::__1::default_delete<swift::RegionAnalysisFunctionInfo>>>>::clear() (.cold.1) + 0
8  swift-frontend           0x0000000104af76a4 swift::SILIsolationInfo::SILIsolationInfo(swift::ActorIsolation, swift::SILValue, swift::SILValue) + 180
9  swift-frontend           0x0000000104f6e4a0 swift::SILIsolationInfo::get(swift::SILInstruction*) + 1964
10 swift-frontend           0x0000000104aec994 swift::regionanalysisimpl::PartitionOpTranslator::translateSILPartialApply(swift::PartialApplyInst*) + 860
11 swift-frontend           0x0000000104ae6094 swift::regionanalysisimpl::PartitionOpTranslator::translateSILInstruction(swift::SILInstruction*)::'lambda0'()::operator()() const + 1504
12 swift-frontend           0x0000000104ae51fc swift::regionanalysisimpl::PartitionOpTranslator::translateSILInstruction(swift::SILInstruction*) + 136
13 swift-frontend           0x0000000104adf27c swift::regionanalysisimpl::PartitionOpTranslator::translateSILBasicBlock(swift::SILBasicBlock*, std::__1::vector<swift::PartitionOp, std::__1::allocator<swift::PartitionOp>>&) + 864
14 swift-frontend           0x0000000104af87e8 swift::BasicBlockData<swift::regionanalysisimpl::BlockPartitionState, 32u>::BasicBlockData(swift::SILFunction*, llvm::function_ref<swift::regionanalysisimpl::BlockPartitionState (swift::SILBasicBlock*)>) + 196
15 swift-frontend           0x0000000104ae0488 swift::RegionAnalysisFunctionInfo::RegionAnalysisFunctionInfo(swift::SILFunction*, swift::PostOrderFunctionInfo*) + 568
16 swift-frontend           0x0000000104ae29fc swift::RegionAnalysis::newFunctionAnalysis(swift::SILFunction*) + 56
17 swift-frontend           0x0000000104d2bc18 swift::FunctionAnalysisBase<swift::RegionAnalysisFunctionInfo>::get(swift::SILFunction*) + 80
18 swift-frontend           0x0000000104d2b93c (anonymous namespace)::TransferNonSendable::run() + 124
19 swift-frontend           0x0000000104d4c11c swift::SILPassManager::runPassOnFunction(unsigned int, swift::SILFunction*) + 1432
20 swift-frontend           0x0000000104d4cf88 swift::SILPassManager::runFunctionPasses(unsigned int, unsigned int) + 1060
21 swift-frontend           0x0000000104d4f8d8 swift::SILPassManager::execute() + 596
22 swift-frontend           0x0000000104d4a0fc swift::SILPassManager::executePassPipelinePlan(swift::SILPassPipelinePlan const&) + 72
23 swift-frontend           0x0000000104d4a07c swift::ExecuteSILPipelineRequest::evaluate(swift::Evaluator&, swift::SILPipelineExecutionDescriptor) const + 68
24 swift-frontend           0x0000000104d857e4 swift::SimpleRequest<swift::ExecuteSILPipelineRequest, std::__1::tuple<> (swift::SILPipelineExecutionDescriptor), (swift::RequestFlags)1>::evaluateRequest(swift::ExecuteSILPipelineRequest const&, swift::Evaluator&) + 28
25 swift-frontend           0x0000000104d65f4c swift::ExecuteSILPipelineRequest::OutputType swift::Evaluator::getResultUncached<swift::ExecuteSILPipelineRequest, swift::ExecuteSILPipelineRequest::OutputType swift::evaluateOrFatal<swift::ExecuteSILPipelineRequest>(swift::Evaluator&, swift::ExecuteSILPipelineRequest)::'lambda'()>(swift::ExecuteSILPipelineRequest const&, swift::ExecuteSILPipelineRequest::OutputType swift::evaluateOrFatal<swift::ExecuteSILPipelineRequest>(swift::Evaluator&, swift::ExecuteSILPipelineRequest)::'lambda'()) + 204
26 swift-frontend           0x0000000104d4a2d8 swift::executePassPipelinePlan(swift::SILModule*, swift::SILPassPipelinePlan const&, bool, swift::irgen::IRGenModule*) + 64
27 swift-frontend           0x0000000104d68404 swift::runSILDiagnosticPasses(swift::SILModule&) + 192
28 swift-frontend           0x00000001045ace38 swift::CompilerInstance::performSILProcessing(swift::SILModule*) + 68
29 swift-frontend           0x0000000104371d24 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*) + 796
30 swift-frontend           0x000000010437165c swift::performCompileStepsPostSema(swift::CompilerInstance&, int&, swift::FrontendObserver*) + 1160
31 swift-frontend           0x000000010438266c withSemanticAnalysis(swift::CompilerInstance&, swift::FrontendObserver*, llvm::function_ref<bool (swift::CompilerInstance&)>, bool) + 160
32 swift-frontend           0x0000000104373a48 performCompile(swift::CompilerInstance&, int&, swift::FrontendObserver*) + 708
33 swift-frontend           0x00000001043729b4 swift::performFrontend(llvm::ArrayRef<char const*>, char const*, void*, swift::FrontendObserver*) + 2368
34 swift-frontend           0x000000010418d240 swift::mainEntry(int, char const**) + 3096
35 dyld                     0x000000019ae360e0 start + 2360

Expected behavior

The compiler should not crash.

Environment

Apple Swift version 6.0-dev (LLVM 2c365f15bfc9eae, Swift 4e30159)
Target: arm64-apple-macosx14.0

Additional information

No response