func foo(x: Int) {
    func inner(y: Int = x) {
        print(y)
    }
    inner()
}

foo(x: 12)

$ swiftc testcapture.swift 
Global is external, but doesn't have external or weak linkage!
i8* ()* @_TFF11testcapture3fooFT1xSi_T_auL_1xSi
LLVM ERROR: Broken module found, compilation aborted!

func foo(x: Int) {
    func inner(y: Int = { x }()) {
        print(y)
    }
    inner()
}

foo(x: 12)

0  swift                    0x000000010d146677 PrintStackTraceSignalHandler(void*) + 39
1  swift                    0x000000010d145b26 SignalHandler(int) + 646
2  libsystem_platform.dylib 0x00007fffa089bbba _sigtramp + 26
3  libsystem_platform.dylib 0x00007fa34c817d00 _sigtramp + 2885140832
4  swift                    0x000000010a2594a5 (anonymous namespace)::SILGenApply::visitAbstractClosureExpr(swift::AbstractClosureExpr*) + 869
5  swift                    0x000000010a25a0d2 (anonymous namespace)::SILGenApply::visitApplyExpr(swift::ApplyExpr*) + 1186
6  swift                    0x000000010a24a317 prepareApplyExpr(swift::Lowering::SILGenFunction&, swift::Expr*) + 263
7  swift                    0x000000010a297f10 swift::ASTVisitor<(anonymous namespace)::RValueEmitter, swift::Lowering::RValue, void, void, void, void, void, swift::Lowering::SGFContext>::visit(swift::Expr*, swift::Lowering::SGFContext) + 112
8  swift                    0x000000010a2f5c93 swift::Lowering::SILGenFunction::emitReturnExpr(swift::SILLocation, swift::Expr*) + 467
9  swift                    0x000000010a2b7901 swift::Lowering::SILGenFunction::emitGeneratorFunction(swift::SILDeclRef, swift::Expr*) + 737
10 swift                    0x000000010a234c77 swift::Lowering::SILGenModule::emitAbstractFuncDecl(swift::AbstractFunctionDecl*) + 1767
11 swift                    0x000000010a23417f swift::Lowering::SILGenModule::emitFunction(swift::FuncDecl*) + 31
12 swift                    0x000000010a2f54ce swift::ASTVisitor<(anonymous namespace)::StmtEmitter, void, void, void, void, void, void>::visit(swift::Stmt*) + 14750
13 swift                    0x000000010a2b4989 swift::Lowering::SILGenFunction::emitFunction(swift::FuncDecl*) + 409
14 swift                    0x000000010a23580b swift::Lowering::SILGenModule::emitFunction(swift::FuncDecl*)::$_1::operator()(swift::SILFunction*) const + 1867
15 swift                    0x000000010a2343e2 swift::Lowering::SILGenModule::emitFunction(swift::FuncDecl*) + 642
16 swift                    0x000000010a242e61 swift::ASTVisitor<swift::Lowering::SILGenModule, void, void, void, void, void, void>::visit(swift::Decl*) + 657
17 swift                    0x000000010a241ecb swift::Lowering::SILGenModule::emitSourceFile(swift::SourceFile*, unsigned int) + 1659
18 swift                    0x000000010a243af9 swift::SILModule::constructSIL(swift::ModuleDecl*, swift::SILOptions&, swift::FileUnit*, llvm::Optional<unsigned int>, bool, bool) + 1593
19 swift                    0x000000010a067c58 swift::performFrontend(llvm::ArrayRef<char const*>, char const*, void*, swift::FrontendObserver*) + 42392
20 swift                    0x000000010a0174bc main + 9052
21 libdyld.dylib            0x00007fffa068e255 start + 1
22 libdyld.dylib            0x000000000000000f start + 1603739067
Stack dump:
0.  Program arguments: /Applications/Xcode-beta.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swift -frontend -c -primary-file testcapture.swift -target x86_64-apple-macosx10.9 -enable-objc-interop -sdk /Applications/Xcode-beta.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.12.sdk -color-diagnostics -module-name testcapture -o /var/folders/y0/845byh512k53x98tw3ch5j2w0000gn/T/testcapture-50dace.o 
1.  While emitting SIL for 'foo' at testcapture.swift:1:1
2.  While silgen emitDefaultArgGenerator  SIL function @_TIFF11testcapture3fooFT1xSi_T_L_5innerFT1ySi_T_A_ for expression at [testcapture.swift:2:23 - line:2:27] RangeText="{x}()"
<unknown>:0: error: unable to execute command: Segmentation fault: 11
<unknown>:0: error: compile command failed due to signal (use -v to see invocation)