[SR-16028] Compiler Crash When Mapping via KeyPath

[swift-ci]

Previous ID	SR-16028
Radar	None
Original Reporter	VaslD (JIRA User)
Type	Bug

Attachment: Download

Environment

macOS: 12.3 (21E230)

Xcode: 13.3 (13E113)

Mac: Mac mini (2018)

I think the exact issue occurs on M1 Macs as well. The compiler also crashed compiling our production code on a CI Mac. But I did not re-submit and check if the demo project would cause a crash.

Additional Detail from JIRA

Votes	0
Component/s	Compiler
Labels	Bug, CompilerCrash
Assignee	None
Priority	Medium

md5: 28d3740145e9822f99d78e5996d1b107

Issue Description:

1.  Apple Swift version 5.6 (swiftlang-5.6.0.323.62 clang-1316.0.20.8)
2.  Compiling with the current language version
3.  While evaluating request IRGenRequest(IR Generation for file "/Users/vasld/Desktop/Swift Helpers/Swift Helpers/Demo/UnitTestClass.swift")
4.  While emitting IR SIL function "@$s4Demo5TestFC10testMethodyyFZ".
 for 'testMethod()' (at /Users/vasld/Desktop/Swift Helpers/Swift Helpers/Demo/UnitTestClass.swift:5:5)
Stack dump without symbol names (ensure you have llvm-symbolizer in your PATH or set the environment var `LLVM_SYMBOLIZER_PATH` to point to it):
0  swift-frontend           0x0000000113bd6de7 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) + 39
1  swift-frontend           0x0000000113bd5e38 llvm::sys::RunSignalHandlers() + 248
2  swift-frontend           0x0000000113bd7440 SignalHandler(int) + 288
3  libsystem_platform.dylib 0x00007ff80a377dfd _sigtramp + 29
4  libsystem_platform.dylib 000000000000000000 _sigtramp + 18446603370409525792
5  swift-frontend           0x000000010fbb8679 swift::Mangle::ASTMangler::appendAnyProtocolConformance(swift::GenericSignature, swift::CanType, swift::ProtocolConformanceRef) + 233
6  swift-frontend           0x000000010ee65828 swift::irgen::IRGenMangler::mangleSymbolNameForMangledConformanceAccessorString(char const*, swift::CanGenericSignature, swift::CanType, swift::ProtocolConformanceRef) + 200
7  swift-frontend           0x000000010edfa422 swift::irgen::IRGenModule::emitWitnessTableRefString(swift::CanType, swift::ProtocolConformanceRef, swift::GenericSignature, bool) + 546
8  swift-frontend           0x000000010edb09ea void llvm::function_ref<void (swift::irgen::GenericRequirement)>::callback_fn<emitKeyPathComponent(swift::irgen::IRGenModule&, swift::irgen::ConstantStructBuilder&, swift::KeyPathPatternComponent const&, bool, swift::GenericEnvironment*, llvm::ArrayRef<swift::irgen::GenericRequirement>, swift::CanType, llvm::ArrayRef<KeyPathIndexOperand>, bool)::$_5>(long, swift::irgen::GenericRequirement) + 378
9  swift-frontend           0x000000010ede90cf swift::irgen::enumerateGenericSignatureRequirements(swift::CanGenericSignature, llvm::function_ref<void (swift::irgen::GenericRequirement)> const&) + 415
10 swift-frontend           0x000000010edaa7d7 emitKeyPathComponent(swift::irgen::IRGenModule&, swift::irgen::ConstantStructBuilder&, swift::KeyPathPatternComponent const&, bool, swift::GenericEnvironment*, llvm::ArrayRef<swift::irgen::GenericRequirement>, swift::CanType, llvm::ArrayRef<KeyPathIndexOperand>, bool) + 1351
11 swift-frontend           0x000000010eda9bd6 swift::irgen::IRGenModule::getAddrOfKeyPathPattern(swift::KeyPathPattern*, swift::SILLocation) + 2310
12 swift-frontend           0x000000010ee7b57e swift::SILInstructionVisitor<(anonymous namespace)::IRGenSILFunction, void>::visit(swift::SILInstruction*) + 5086
13 swift-frontend           0x000000010ee74e32 swift::irgen::IRGenModule::emitSILFunction(swift::SILFunction*) + 10530
14 swift-frontend           0x000000010ed1d6d3 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&) + 1875
15 swift-frontend           0x000000010ee3f889 swift::IRGenRequest::evaluate(swift::Evaluator&, swift::IRGenDescriptor) const + 9513
16 swift-frontend           0x000000010ee721ec swift::SimpleRequest<swift::IRGenRequest, swift::GeneratedModule (swift::IRGenDescriptor), (swift::RequestFlags)9>::evaluateRequest(swift::IRGenRequest const&, swift::Evaluator&) + 204
17 swift-frontend           0x000000010ee4a47c llvm::Expected<swift::IRGenRequest::OutputType> swift::Evaluator::getResultUncached<swift::IRGenRequest>(swift::IRGenRequest const&) + 828
18 swift-frontend           0x000000010ee4416c 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**) + 348
19 swift-frontend           0x000000010e90d3b3 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*) + 2499
20 swift-frontend           0x000000010e8ff261 swift::performFrontend(llvm::ArrayRef<char const*>, char const*, void*, swift::FrontendObserver*) + 15233
21 swift-frontend           0x000000010e8be5d4 swift::mainEntry(int, char const**) + 1108
22 dyld                     0x000000011d69651e start + 462

When compiling the following Swift class:

import Foundation

@objc(TestF)
class TestF: NSObject, UnitTestProtocol {
    static public func testMethod() {
        let errors = self.catchErrors()
        _ = errors.map(\.localizedDescription).joined(separator: "\n")
    }

    static public func testName() -> String! {
        return "测试 F"
    }

    static func catchErrors() -> [Error] {
        return []
    }
}

Not sure if related, the class is exported to Obj-C and implements Obj-C bridged protocol.

Build failure went away when description-mapping line was removed.

Reproduction project attached below.

[stackotter]

Here's a reduced reproducing example:

import Foundation

let errors: [Error] = []
_ = errors.map(\.localizedDescription)

[AnthonyLatsis]

Can be reduced further:

import Foundation

let k = \Error.localizedDescription

[AnthonyLatsis]

A self-contained reproducer:

// Module A
public protocol P {}
extension P {
  public var foo: Bool { true }
}

// Module B
import A
let kp = \P.foo

We need to emit a property descriptor for the external key path component here. Normally, the substitutions of an external component are mapped out of context, but that does not apply to opened archetypes, so we end up referencing an opened archetype in the keypath instruction (which may be fine), and having to emit a witness table ref for the conformance of Self to the opened archetype. The latter fails because ASTMangler::appendAnyProtocolConformance does not expect the conforming type to be an opened archetype. I feel like there's something fishy about emitting these WT refs for every opened archetype, but mapping them out of context tends to always be the wrong answer.

CC @slavapestov @jckarter

[slavapestov]

We need to add a new keypath component kind for opening existentials.

[AnthonyLatsis]

Am I right in assuming that the accessors emitted for this new component kind would accept the opened existential generically, rather than opening it in place?

[n8chur]

I've also experienced this issue in the shape of @AnthonyLatsis's latest example. I packaged a repro here.

[jckarter]

@AnthonyLatsis Thanks for looking into this! I think @slavapestov's idea of having a new key path component kind for opening is conceptually good, but unfortunately I'm not sure it'll fit in the existing implementation model, since the rest of the implementation of key paths assume that each component in an instantiated key path has a concrete root and value type, which wouldn't be true for the opened type in an existential. Maybe we could fit support for opened types into the implementation model somehow, but another way we could handle them is to have the runtime provide getter/setter thunks that can be used to form a computed key path component, which open the existential then invoke the getter/setter entry points from the property descriptor.