Open Radar

 
Summary:
Defer is a very convenient workaround for failable initialisers requiring to call super before returning nil. Sadly it crashes compiler

Steps to Reproduce:
Try running following code

class B {
    init() {
    }
}

class A: B {
    override init() {
        defer {
            super.init()
        }
    }
}

let a = A()


Expected Results:
Initialisation should be invoked as the very last thing happening during initialisation.

Actual Results:
Compiler crashes with 
0  swift                    0x0000000110fbfedb llvm::sys::PrintStackTrace(__sFILE*) + 43
1  swift                    0x0000000110fc061b SignalHandler(int) + 379
4  swift                    0x000000010f2abddd swift::ASTVisitor<(anonymous namespace)::RValueEmitter, swift::Lowering::RValue, void, void, void, void, void, swift::Lowering::SGFContext>::visit(swift::Expr*, swift::Lowering::SGFContext) + 24749
5  swift                    0x000000010f2a44ad swift::Lowering::SILGenFunction::emitIgnoredExpr(swift::Expr*) + 397
6  swift                    0x000000010f2e4e46 swift::ASTVisitor<(anonymous namespace)::StmtEmitter, void, void, void, void, void, void>::visit(swift::Stmt*) + 294
7  swift                    0x000000010f2e4d15 swift::Lowering::SILGenFunction::emitStmt(swift::Stmt*) + 21
8  swift                    0x000000010f2b5e7b swift::Lowering::SILGenFunction::emitFunction(swift::FuncDecl*) + 331
9  swift                    0x000000010f272a20 std::__1::__function::__func<swift::Lowering::SILGenModule::emitFunction(swift::FuncDecl*)::$_1, std::__1::allocator<swift::Lowering::SILGenModule::emitFunction(swift::FuncDecl*)::$_1>, void (swift::SILFunction*)>::operator()(swift::SILFunction*&&) + 128
10 swift                    0x000000010f272474 swift::SILModule::constructSIL(swift::ModuleDecl*, swift::SILOptions&, swift::FileUnit*, llvm::Optional<unsigned int>, bool, bool) + 1268
11 swift                    0x000000010f2726dd swift::performSILGeneration(swift::FileUnit&, swift::SILOptions&, llvm::Optional<unsigned int>, bool) + 109
12 swift                    0x000000010f0d0fd5 performCompile(swift::CompilerInstance&, swift::CompilerInvocation&, llvm::ArrayRef<char const*>, int&) + 11445
13 swift                    0x000000010f0ce10a frontend_main(llvm::ArrayRef<char const*>, char const*, void*) + 2682
14 swift                    0x000000010f0ca797 main + 2247