Referring to functions with parameter packs as closures crashes the compiler.

[JessyCatterwaul]

func ƒ<each T>(_: repeat each T) { }

_ = { ƒ() } // fine
_ = ƒ as () -> _ // Command SwiftCompile failed with a nonzero exit code

[AnthonyLatsis]

Stack dump:

Assertion failed: (N+M <= size() && "Invalid specifier"), function slice, file ArrayRef.h, line 195.
Please submit a bug report (https://swift.org/contributing/#reporting-bugs) and include the crash backtrace.
Stack dump:
0.	Program arguments: bin/swift-frontend /Users/mac/Desktop/test.swift -emit-ir
1.	Swift version 5.9-dev (LLVM d638e0929fa87b0, Swift 23e2f345b51ca0c)
2.	Compiling with the current language version
3.	While evaluating request ASTLoweringRequest(Lowering AST to SIL for module test)
4.	While emitting reabstraction thunk in SIL function "@$syQSiIegp_Ieg_TR".
 for <<debugloc at "<compiler-generated>":0:0>>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           0x0000000109f89117 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) + 39
1  swift-frontend           0x0000000109f883f5 llvm::sys::RunSignalHandlers() + 85
2  swift-frontend           0x0000000109f89760 SignalHandler(int) + 288
3  libsystem_platform.dylib 0x00007ff815a94dfd _sigtramp + 29
4  swift-frontend           0x0000000105d596e9 swift::Type::transformWithPosition(swift::TypePosition, llvm::function_ref<llvm::Optional<swift::Type> (swift::TypeBase*, swift::TypePosition)>) const + 73
5  libsystem_c.dylib        0x00007ff8159cad24 abort + 123
6  libsystem_c.dylib        0x00007ff8159ca0cb err + 0
7  swift-frontend           0x000000010a187fe3 (anonymous namespace)::TranslateArguments::translate(swift::Lowering::AbstractionPattern, swift::ArrayRefView<swift::AnyFunctionType::Param, swift::AnyFunctionType::CanParam, swift::AnyFunctionType::CanParam::getFromParam(swift::AnyFunctionType::Param const&), true>, swift::Lowering::AbstractionPattern, swift::ArrayRefView<swift::AnyFunctionType::Param, swift::AnyFunctionType::CanParam, swift::AnyFunctionType::CanParam::getFromParam(swift::AnyFunctionType::Param const&), true>, bool) (.cold.15) + 35
8  swift-frontend           0x0000000104b42deb (anonymous namespace)::TranslateArguments::translate(swift::Lowering::AbstractionPattern, swift::ArrayRefView<swift::AnyFunctionType::Param, swift::AnyFunctionType::CanParam, swift::AnyFunctionType::CanParam::getFromParam(swift::AnyFunctionType::Param const&), true>, swift::Lowering::AbstractionPattern, swift::ArrayRefView<swift::AnyFunctionType::Param, swift::AnyFunctionType::CanParam, swift::AnyFunctionType::CanParam::getFromParam(swift::AnyFunctionType::Param const&), true>, bool) + 4891
9  swift-frontend           0x0000000104b47d3e createThunk(swift::Lowering::SILGenFunction&, swift::SILLocation, swift::Lowering::ManagedValue, swift::Lowering::AbstractionPattern, swift::CanTypeWrapper<swift::AnyFunctionType>, swift::Lowering::AbstractionPattern, swift::CanTypeWrapper<swift::AnyFunctionType>, swift::Lowering::TypeLowering const&) + 5454
10 swift-frontend           0x0000000104b3e2fb (anonymous namespace)::Transform::transform(swift::Lowering::ManagedValue, swift::Lowering::AbstractionPattern, swift::CanType, swift::Lowering::AbstractionPattern, swift::CanType, swift::SILType, swift::Lowering::SGFContext) + 3547
11 swift-frontend           0x0000000104b3c912 swift::Lowering::SILGenFunction::emitOrigToSubstValue(swift::SILLocation, swift::Lowering::ManagedValue, swift::Lowering::AbstractionPattern, swift::CanType, swift::Lowering::SGFContext) + 242
12 swift-frontend           0x0000000104afd130 swift::Lowering::SILGenFunction::emitClosureValue(swift::SILLocation, swift::SILDeclRef, swift::CanType, swift::SubstitutionMap, bool) + 1488
13 swift-frontend           0x0000000104ad52be swift::Lowering::SILGenFunction::emitRValueForDecl(swift::SILLocation, swift::ConcreteDeclRef, swift::Type, swift::AccessSemantics, swift::Lowering::SGFContext) + 430
14 swift-frontend           0x0000000104ae13ac swift::ASTVisitor<(anonymous namespace)::RValueEmitter, swift::Lowering::RValue, void, void, void, void, void, swift::Lowering::SGFContext>::visit(swift::Expr*, swift::Lowering::SGFContext) + 2412
15 swift-frontend           0x0000000104ad76c6 swift::Lowering::SILGenFunction::emitIgnoredExpr(swift::Expr*) + 1142
16 swift-frontend           0x0000000104ae38b4 swift::ASTVisitor<(anonymous namespace)::RValueEmitter, swift::Lowering::RValue, void, void, void, void, void, swift::Lowering::SGFContext>::visit(swift::Expr*, swift::Lowering::SGFContext) + 11892
17 swift-frontend           0x0000000104ad76c6 swift::Lowering::SILGenFunction::emitIgnoredExpr(swift::Expr*) + 1142
18 swift-frontend           0x0000000104a6a173 swift::Lowering::SILGenModule::visitTopLevelCodeDecl(swift::TopLevelCodeDecl*) + 275
19 swift-frontend           0x0000000104a6ac05 swift::ASTLoweringRequest::evaluate(swift::Evaluator&, swift::ASTLoweringDescriptor) const + 2261
20 swift-frontend           0x0000000104b58808 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&) + 120
21 swift-frontend           0x0000000104a6f2e3 llvm::Expected<swift::ASTLoweringRequest::OutputType> swift::Evaluator::getResultUncached<swift::ASTLoweringRequest>(swift::ASTLoweringRequest const&) + 387
22 swift-frontend           0x0000000104a6bfd1 swift::performASTLowering(swift::ModuleDecl*, swift::Lowering::TypeConverter&, swift::SILOptions const&, swift::IRGenOptions const*) + 161
23 swift-frontend           0x000000010441fd62 swift::performCompileStepsPostSema(swift::CompilerInstance&, int&, swift::FrontendObserver*) + 2290
24 swift-frontend           0x0000000104422bd6 performCompile(swift::CompilerInstance&, int&, swift::FrontendObserver*) + 950
25 swift-frontend           0x0000000104421929 swift::performFrontend(llvm::ArrayRef<char const*>, char const*, void*, swift::FrontendObserver*) + 3321
26 swift-frontend           0x00000001043bc06a swift::mainEntry(int, char const**) + 2282
27 dyld                     0x0000000126b2652e start + 462
Abort trap: 6