Variadic generics crash with Embedded Swift in SILCloner

[MaxDesiatov]

Description

When building a snippet that contains variadic generics with swiftc -enable-experimental-feature Embedded -wmo repro.swift with latest development snapshot of the main branch of the toolchain, the compiler crashes in swift::SILCloner.

Reproduction

struct Mixer<each Source: Signal>: Signal {
  var sources: (repeat each Source)

  mutating func next() -> Float {
    var result: Float = 0

    sources = (repeat (each sources).next(accumulatingInto: &result))

    return result
  }
}

protocol Signal {
  mutating func next() -> Float
}

extension Signal {
  consuming func next(accumulatingInto: inout Float) -> Self {
    accumulatingInto += self.next()
    return self
  }
}

struct Constant: Signal { func next() -> Float { 42 } }

var mixer = Mixer(sources: Constant())
if mixer.next() == 42 {
  print("forty two")
} else {
  print("not forty two")
}

Stack dump

1.      Apple Swift version 6.0-dev (LLVM 7fe091223bc821e, Swift 92f5eeeefc88005)
2.      Compiling with effective version 5.10
3.      While evaluating request ExecuteSILPipelineRequest(Run pipelines { Non-Diagnostic Mandatory Optimizations, Serialization, Rest of Onone } on SIL for repro)
4.      While running pass #342 SILModuleTransform "CrossModuleOptimization".
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           0x00000001057d2e18 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) + 56
1  swift-frontend           0x00000001057d15e4 llvm::sys::RunSignalHandlers() + 112
2  swift-frontend           0x00000001057d3460 SignalHandler(int) + 304
3  libsystem_platform.dylib 0x00000001970e3584 _sigtramp + 56
4  swift-frontend           0x0000000100bfd6bc swift::SILCloner<(anonymous namespace)::InstructionVisitor>::doesOpTupleDisappear(swift::CanTypeWrapper<swift::TupleType>) + 260
5  swift-frontend           0x0000000100bf7208 (anonymous namespace)::InstructionVisitor::makeTypesUsableFromInline(swift::SILInstruction*, (anonymous namespace)::CrossModuleOptimization&) + 11384
6  swift-frontend           0x0000000100bf2f18 (anonymous namespace)::CrossModuleOptimization::serializeFunction(swift::SILFunction*, llvm::DenseMap<swift::SILFunction*, bool, llvm::DenseMapInfo<swift::SILFunction*, void>, llvm::detail::DenseMapPair<swift::SILFunction*, bool>> const&) + 268
7  swift-frontend           0x0000000100bf282c (anonymous namespace)::CrossModuleOptimizationPass::run() + 308
8  swift-frontend           0x0000000100d85e08 swift::SILPassManager::runModulePass(unsigned int) + 856
9  swift-frontend           0x0000000100d88174 swift::SILPassManager::execute() + 624
10 swift-frontend           0x0000000100d829ec swift::SILPassManager::executePassPipelinePlan(swift::SILPassPipelinePlan const&) + 72
11 swift-frontend           0x0000000100d8296c swift::ExecuteSILPipelineRequest::evaluate(swift::Evaluator&, swift::SILPipelineExecutionDescriptor) const + 68
12 swift-frontend           0x0000000100dbdd68 swift::SimpleRequest<swift::ExecuteSILPipelineRequest, std::__1::tuple<> (swift::SILPipelineExecutionDescriptor), (swift::RequestFlags)1>::evaluateRequest(swift::ExecuteSILPipelineRequest const&, swift::Evaluator&) + 28
13 swift-frontend           0x0000000100d9e63c 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
14 swift-frontend           0x0000000100d82bc8 swift::executePassPipelinePlan(swift::SILModule*, swift::SILPassPipelinePlan const&, bool, swift::irgen::IRGenModule*) + 64
15 swift-frontend           0x0000000100da0d48 swift::runSILPassesForOnone(swift::SILModule&) + 80
16 swift-frontend           0x00000001005edc34 swift::CompilerInstance::performSILProcessing(swift::SILModule*) + 252
17 swift-frontend           0x00000001003b3dec 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
18 swift-frontend           0x00000001003b3724 swift::performCompileStepsPostSema(swift::CompilerInstance&, int&, swift::FrontendObserver*) + 1164
19 swift-frontend           0x00000001003c465c withSemanticAnalysis(swift::CompilerInstance&, swift::FrontendObserver*, llvm::function_ref<bool (swift::CompilerInstance&)>, bool) + 160
20 swift-frontend           0x00000001003b5b10 performCompile(swift::CompilerInstance&, int&, swift::FrontendObserver*) + 708
21 swift-frontend           0x00000001003b4a7c swift::performFrontend(llvm::ArrayRef<char const*>, char const*, void*, swift::FrontendObserver*) + 2368
22 swift-frontend           0x00000001001eb4dc swift::mainEntry(int, char const**) + 3096
23 dyld                     0x0000000196d2a0e0 start + 2360

Expected behavior

Variadic generics snippet compiles successfully or an actionable diagnostic error message is produced.

Environment

Apple Swift version 6.0-dev (LLVM 7fe091223bc821e, Swift 92f5eee)
Target: arm64-apple-macosx14.0

Additional information

No response

[persidskiy]

Hi, I am experiencing the same issue when compiling the following code with Whole Module Optimization and Testability enabled. There is no crash if I compile it either without WMO or testability.

Xcode: 15.3, Swift: 5.10.

public protocol View {}

public struct TupleView<T>: View {
    var children: T
    init<each Content>(_ content: repeat each Content)
        where repeat each Content: View, T == (repeat each Content) {
        children = (repeat each content)
    }
}

@resultBuilder
public struct ViewBuilder {
    public static func buildBlock<each Content>(_ content: repeat each Content) -> TupleView<(repeat each Content)> where repeat each Content: View {
        TupleView(repeat each content)
    }
}

A minimal reproducible SPM project is here: https://github.com/persidskiy/swift-wmo-crash

Stacktrace:

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 ExecuteSILPipelineRequest(Run pipelines { PrepareOptimizationPasses, EarlyModulePasses, HighLevel,Function+EarlyLoopOpt, HighLevel,Module+StackPromote, MidLevel,Function, ClosureSpecialize, LowLevel,Function, LateLoopOpt, SIL Debug Info Generator } on SIL for swift_crash)
4.      While running pass #1244 SILModuleTransform "CrossModuleOptimization".
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           0x0000000109de7f3c llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) + 56
1  swift-frontend           0x0000000109de70f8 llvm::sys::RunSignalHandlers() + 112
2  swift-frontend           0x0000000109de8544 SignalHandler(int) + 360
3  libsystem_platform.dylib 0x000000018d3f9a24 _sigtramp + 56
4  swift-frontend           0x0000000104f60fb4 swift::SILCloner<(anonymous namespace)::InstructionVisitor>::doesOpTupleDisappear(swift::CanTypeWrapper<swift::TupleType>) + 300
5  swift-frontend           0x0000000104f5b89c (anonymous namespace)::InstructionVisitor::makeTypesUsableFromInline(swift::SILInstruction*, (anonymous namespace)::CrossModuleOptimization&) + 4276
6  swift-frontend           0x0000000104f58fb0 (anonymous namespace)::CrossModuleOptimization::serializeFunction(swift::SILFunction*, llvm::DenseMap<swift::SILFunction*, bool, llvm::DenseMapInfo<swift::SILFunction*, void>, llvm::detail::DenseMapPair<swift::SILFunction*, bool>> const&) + 228
7  swift-frontend           0x0000000104f587f8 (anonymous namespace)::CrossModuleOptimizationPass::run() + 468
8  swift-frontend           0x0000000105120978 swift::SILPassManager::executePassPipelinePlan(swift::SILPassPipelinePlan const&) + 16476
9  swift-frontend           0x0000000105159354 swift::SimpleRequest<swift::ExecuteSILPipelineRequest, std::__1::tuple<> (swift::SILPipelineExecutionDescriptor), (swift::RequestFlags)1>::evaluateRequest(swift::ExecuteSILPipelineRequest const&, swift::Evaluator&) + 56
10 swift-frontend           0x000000010513d184 llvm::Expected<swift::ExecuteSILPipelineRequest::OutputType> swift::Evaluator::getResultUncached<swift::ExecuteSILPipelineRequest>(swift::ExecuteSILPipelineRequest const&) + 476
11 swift-frontend           0x000000010513fe94 swift::runSILOptimizationPasses(swift::SILModule&) + 504
12 swift-frontend           0x00000001048f516c swift::CompilerInstance::performSILProcessing(swift::SILModule*) + 1224
13 swift-frontend           0x00000001046e5f98 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*) + 1128
14 swift-frontend           0x00000001046e5a18 swift::performCompileStepsPostSema(swift::CompilerInstance&, int&, swift::FrontendObserver*) + 2100
15 swift-frontend           0x00000001046e9694 performCompile(swift::CompilerInstance&, int&, swift::FrontendObserver*) + 1448
16 swift-frontend           0x00000001046e76d0 swift::performFrontend(llvm::ArrayRef<char const*>, char const*, void*, swift::FrontendObserver*) + 4968
17 swift-frontend           0x0000000104676e8c swift::mainEntry(int, char const**) + 2612
18 dyld                     0x000000018d0490e0 start + 2360