Subscripts that use type placeholders crash the compiler.

[JessyCatterwaul]

Description

No response

Reproduction

enum E {
  subscript() -> _ { }
}

Stack dump

0  swift-frontend           0x0000000108b39994 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) + 56
1  swift-frontend           0x0000000108b37324 llvm::sys::RunSignalHandlers() + 112
2  swift-frontend           0x0000000108b39fc0 SignalHandler(int, __siginfo*, void*) + 344
3  libsystem_platform.dylib 0x000000019c6aa704 _sigtramp + 56
4  swift-frontend           0x0000000103147708 swift::Lowering::TypeConverter::getTypeLowering(swift::Lowering::AbstractionPattern, swift::Type, swift::TypeExpansionContext) + 540
5  swift-frontend           0x00000001030a033c (anonymous namespace)::DestructureResults::destructure(swift::Lowering::AbstractionPattern, swift::CanType) + 116
6  swift-frontend           0x000000010309e118 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) + 2920
7  swift-frontend           0x0000000103095540 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) + 684
8  swift-frontend           0x0000000103098380 getUncachedSILFunctionTypeForConstant(swift::Lowering::TypeConverter&, swift::TypeExpansionContext, swift::SILDeclRef, swift::Lowering::TypeConverter::LoweredFormalTypes) + 1392
9  swift-frontend           0x0000000103098fac swift::Lowering::TypeConverter::getConstantInfo(swift::TypeExpansionContext, swift::SILDeclRef) + 200
10 swift-frontend           0x000000010308ec38 swift::SILFunctionBuilder::getOrCreateFunction(swift::SILLocation, swift::SILDeclRef, swift::ForDefinition_t, llvm::function_ref<swift::SILFunction* (swift::SILLocation, swift::SILDeclRef)>, swift::ProfileCounter) + 124
11 swift-frontend           0x00000001032732b8 swift::Lowering::SILGenModule::getFunction(swift::SILDeclRef, swift::ForDefinition_t) + 728
12 swift-frontend           0x0000000103276fb8 swift::Lowering::SILGenModule::emitOrDelayFunction(swift::SILDeclRef) + 220
13 swift-frontend           0x0000000103274224 swift::Lowering::SILGenModule::emitFunction(swift::FuncDecl*) + 136
14 swift-frontend           0x00000001033db1ec (anonymous namespace)::SILGenType::visitFuncDecl(swift::FuncDecl*) + 32
15 swift-frontend           0x00000001033db3ec (anonymous namespace)::SILGenType::visitAbstractStorageDecl(swift::AbstractStorageDecl*) + 248
16 swift-frontend           0x00000001033d6f6c (anonymous namespace)::SILGenType::emitType() + 488
17 swift-frontend           0x0000000103273f38 swift::ASTVisitor<swift::Lowering::SILGenModule, void, void, void, void, void, void>::visit(swift::Decl*) + 100
18 swift-frontend           0x000000010327add4 swift::ASTLoweringRequest::evaluate(swift::Evaluator&, swift::ASTLoweringDescriptor) const + 2364
19 swift-frontend           0x00000001033be328 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&) + 208
20 swift-frontend           0x000000010327f85c 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'()) + 572
21 swift-frontend           0x000000010278722c swift::performCompileStepsPostSema(swift::CompilerInstance&, int&, swift::FrontendObserver*) + 964
22 swift-frontend           0x000000010278a5a0 performCompile(swift::CompilerInstance&, int&, swift::FrontendObserver*) + 1764
23 swift-frontend           0x00000001027891b0 swift::performFrontend(llvm::ArrayRef<char const*>, char const*, void*, swift::FrontendObserver*) + 3580
24 swift-frontend           0x000000010270a838 swift::mainEntry(int, char const**) + 5412
25 dyld                     0x000000019c2e9924 start + 6400

Expected behavior

Type placeholder may not appear in subscript return type

Environment

swift-driver version: 1.127.8 Apple Swift version 6.2 (swiftlang-6.2.0.13.10 clang-1700.3.13.4)

Additional information

No response