[SR-2189] Nested function with local default value crashes

[karwa]

Previous ID	SR-2189
Radar	rdar://problem/20796451
Original Reporter	@karwa
Type	Bug
Status	Resolved
Resolution	Done

Environment

Swift 0712ffc

Additional Detail from JIRA

Votes	0
Component/s	Compiler
Labels	Bug, CompilerCrash
Assignee	@slavapestov
Priority	Medium

md5: e7a1b64506511d702d810a7be30fa286

is duplicated by:

• SR-2276 Default argument value of scoped function crash
• SR-4189 Crash with default argument reference to local variable
• SR-5503 Compiler crash with nested function with default argument
• SR-5691 Compiler fails badly if default value is computed property of an enum value
• SR-7328 Compiler crash when inner func uses outer func argument as default argument
• SR-7376 Compiler error "Abort trap 6" when parameter default value is itself a parameter
• SR-7466 Compiler crash when referencing instance member as default parameter
• SR-8193 Compiler crashes on local function with default argument which captures a local var
• SR-10644 Swift compiler crash using scoped constants as default values for parameters
• SR-3866 LLVM error when using a parameter as a default value of nested function

relates to:

• SR-7466 Compiler crash when referencing instance member as default parameter

Issue Description:

The following snippet crashes the compiler:

func doSomething() { 
    var aValue = 42 
    func nestedFunc(_ v: Int = aValue) { 
        print("Got \(v)") 
    } 
    nestedFunc() 
    nestedFunc(36)
}

Assertion failed: (!var->getDeclContext()->isLocalContext() && "not a global variable!"), function isGlobalLazilyInitialized, file /Spring/Projects/3rdParty/OpenSource/Apple/swift/lib/SILGen/SILGenGlobalVariable.cpp, line 64.

0  swift                    0x0000000108e00c3b llvm::sys::PrintStackTrace(llvm::raw_ostream&) + 43
1  swift                    0x0000000108dffe66 llvm::sys::RunSignalHandlers() + 70
2  swift                    0x0000000108e01511 SignalHandler(int) + 641
3  libsystem_platform.dylib 0x000000010b60dd7a _sigtramp + 26
4  libsystem_pthread.dylib  0x000000010b6312c8 _pthread_keys + 9720
5  swift                    0x0000000108e0115e abort + 14
6  swift                    0x0000000108e01141 __assert_rtn + 81
7  swift                    0x00000001061a207c swift::Lowering::SILGenFunction::emitGlobalVariableRef(swift::SILLocation, swift::VarDecl*) + 1356
8  swift                    0x0000000106185a04 swift::Lowering::SILGenFunction::emitLValueForDecl(swift::SILLocation, swift::VarDecl*, swift::CanType, swift::AccessKind, swift::AccessSemantics) + 324
9  swift                    0x00000001061a8596 emitLValueForNonMemberVarDecl(swift::Lowering::SILGenFunction&, swift::SILLocation, swift::VarDecl*, swift::CanType, swift::AccessKind, swift::AccessSemantics) + 150
10 swift                    0x00000001061a8464 SILGenLValue::visitDeclRefExpr(swift::DeclRefExpr*, swift::AccessKind) + 228
11 swift                    0x00000001061a6e73 swift::ASTVisitor<SILGenLValue, swift::Lowering::LValue, void, void, void, void, void, swift::AccessKind>::visit(swift::Expr*, swift::AccessKind) + 99
12 swift                    0x00000001061a6d0a swift::Lowering::SILGenFunction::emitLValue(swift::Expr*, swift::AccessKind) + 106
13 swift                    0x000000010618c632 swift::ASTVisitor<(anonymous namespace)::RValueEmitter, swift::Lowering::RValue, void, void, void, void, void, swift::Lowering::SGFContext>::visit(swift::Expr*, swift::Lowering::SGFContext) + 8882
14 swift                    0x0000000106185733 swift::Lowering::SILGenFunction::emitRValue(swift::Expr*, swift::Lowering::SGFContext) + 35
15 swift                    0x00000001061e0617 swift::Lowering::SILGenFunction::emitReturnExpr(swift::SILLocation, swift::Expr*) + 903
16 swift                    0x00000001061a0cb0 swift::Lowering::SILGenFunction::emitGeneratorFunction(swift::SILDeclRef, swift::Expr*) + 320
17 swift                    0x000000010613ad3a swift::Lowering::SILGenModule::emitDefaultArgGenerator(swift::SILDeclRef, swift::Expr*) + 586
18 swift                    0x0000000106137f0e swift::Lowering::SILGenModule::emitAbstractFuncDecl(swift::AbstractFunctionDecl*) + 318
19 swift                    0x00000001061375ae swift::Lowering::SILGenModule::emitFunction(swift::FuncDecl*) + 46
20 swift                    0x00000001061ddb56 swift::ASTVisitor<(anonymous namespace)::StmtEmitter, void, void, void, void, void, void>::visit(swift::Stmt*) + 566
21 swift                    0x00000001061dee20 swift::ASTVisitor<(anonymous namespace)::StmtEmitter, void, void, void, void, void, void>::visit(swift::Stmt*) + 5376
22 swift                    0x00000001061ddad0 swift::ASTVisitor<(anonymous namespace)::StmtEmitter, void, void, void, void, void, void>::visit(swift::Stmt*) + 432
23 swift                    0x00000001061dd915 swift::Lowering::SILGenFunction::emitStmt(swift::Stmt*) + 21
24 swift                    0x000000010619df1a swift::Lowering::SILGenFunction::emitFunction(swift::FuncDecl*) + 362
25 swift                    0x0000000106140b38 swift::Lowering::SILGenModule::emitFunction(swift::FuncDecl*)::$_1::operator()(swift::SILFunction*) const + 216
26 swift                    0x00000001061377e9 swift::Lowering::SILGenModule::emitFunction(swift::FuncDecl*) + 617
27 swift                    0x00000001061e41b0 swift::ASTVisitor<SILGenExtension, void, void, void, void, void, void>::visit(swift::Decl*) + 368
28 swift                    0x00000001061e349b SILGenExtension::emitExtension(swift::ExtensionDecl*) + 59
29 swift                    0x00000001061e3455 swift::Lowering::SILGenModule::visitExtensionDecl(swift::ExtensionDecl*) + 21
30 swift                    0x000000010613d48b swift::Lowering::SILGenModule::emitSourceFile(swift::SourceFile*, unsigned int) + 715
31 swift                    0x000000010613e370 swift::SILModule::constructSIL(swift::ModuleDecl*, swift::SILOptions&, swift::FileUnit*, llvm::Optional<unsigned int>, bool, bool) + 928
32 swift                    0x000000010613e895 swift::performSILGeneration(swift::FileUnit&, swift::SILOptions&, llvm::Optional<unsigned int>, bool) + 117
33 swift                    0x0000000105fac436 performCompile(swift::CompilerInstance&, swift::CompilerInvocation&, llvm::ArrayRef<char const*>, int&, swift::FrontendObserver*) + 13846
34 swift                    0x0000000105fa7b4f swift::performFrontend(llvm::ArrayRef<char const*>, char const*, void*, swift::FrontendObserver*) + 2895
35 swift                    0x0000000105f6a0a0 main + 2448
36 libdyld.dylib            0x000000010b2df255 start + 1
37 libdyld.dylib            0x0000000000000057 start + 4107406851

The use case for doing this was that nestedFunc was being called from a loop (capturing some common logic that gets called in a few branches), and aValue is a cumulative value. We almost always want to use that value, but there is one edge-case where we need to use a different value from a previous iteration.

The same functionality could be achieved by always capturing aValue, making the parameter optional and branching on whether or not an override was given.

[belkadan]

People keep trying to do this; we should consider banning it if we're not able to implement it right away.

@swift-ci create

[slavapestov]

#27220