[torque] Allow atomarStatements in otherwise statements

In the process:
- Convert TryLabelStatements into TryLabelExpressions
- Change TryLabelExpressions to support only single label blocks and de-sugar
  try/labels into nested try/label statements. This allows the code in a label
  block to goto subsequent labels in the same try/label statement.
- Make otherwise expressions either take IdentifierExpressions which get
  converted into simple label names OR atomarStatements, which make useful
  non-label operations, like 'break' and 'continue', useful together with
  otherwise. Non-label otherwise statements get de-sugared into try/label
  blocks.

Bug: v8:7793
Change-Id: Ie56ede6306e2a3182f6aa1bb8750ed418bda01db
Reviewed-on: https://chromium-review.googlesource.com/c/1266997
Commit-Queue: Daniel Clifford <danno@chromium.org>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56447}

src/builtins/base.tq

@@ -968,21 +968,19 @@ macro ToIndex(input: Object, context: Context): Number
 }
 
 macro GetLengthProperty(context: Context, o: Object): Number {
-  let length: Object;
   try {
-    try {
-      return (Cast<JSArray>(o) otherwise CheckArgs).length;
-    }
-    label CheckArgs {
-      const a: JSArgumentsObjectWithLength =
-          Cast<JSArgumentsObjectWithLength>(context, o) otherwise Slow;
-      return Cast<Smi>(length = a.length) otherwise ToLength;
-    }
+    return (Cast<JSArray>(o) otherwise CheckArgs).length;
+  }
+  label CheckArgs {
+    const a: JSArgumentsObjectWithLength =
+        Cast<JSArgumentsObjectWithLength>(context, o) otherwise Slow;
+    const length: Object = a.length;
+    return Cast<Smi>(length) otherwise goto ToLength(length);
   }
   label Slow deferred {
-    return ToLength_Inline(context, GetProperty(context, o, kLengthString));
+    goto ToLength(GetProperty(context, o, kLengthString));
   }
-  label ToLength deferred {
+  label ToLength(length: Object) deferred {
     return ToLength_Inline(context, length);
   }
 }

src/torque/ast.h

@@ -30,7 +30,9 @@ namespace torque {
   V(ElementAccessExpression)             \
   V(AssignmentExpression)                \
   V(IncrementDecrementExpression)        \
-  V(AssumeTypeImpossibleExpression)
+  V(AssumeTypeImpossibleExpression)      \
+  V(StatementExpression)                 \
+  V(TryLabelExpression)
 
 #define AST_TYPE_EXPRESSION_NODE_KIND_LIST(V) \
   V(BasicTypeExpression)                      \
@@ -52,7 +54,6 @@ namespace torque {
   V(TailCallStatement)                  \
   V(VarDeclarationStatement)            \
   V(GotoStatement)                      \
-  V(TryLabelStatement)
 
 #define AST_DECLARATION_NODE_KIND_LIST(V) \
   V(TypeDeclaration)                      \
@@ -553,15 +554,22 @@ struct LabelBlock : AstNode {
   Statement* body;
 };
 
-struct TryLabelStatement : Statement {
-  DEFINE_AST_NODE_LEAF_BOILERPLATE(TryLabelStatement)
-  TryLabelStatement(SourcePosition pos, Statement* try_block,
-                    std::vector<LabelBlock*> label_blocks)
-      : Statement(kKind, pos),
-        try_block(try_block),
-        label_blocks(std::move(label_blocks)) {}
-  Statement* try_block;
-  std::vector<LabelBlock*> label_blocks;
+struct StatementExpression : Expression {
+  DEFINE_AST_NODE_LEAF_BOILERPLATE(StatementExpression)
+  StatementExpression(SourcePosition pos, Statement* statement)
+      : Expression(kKind, pos), statement(statement) {}
+  Statement* statement;
+};
+
+struct TryLabelExpression : Expression {
+  DEFINE_AST_NODE_LEAF_BOILERPLATE(TryLabelExpression)
+  TryLabelExpression(SourcePosition pos, Expression* try_expression,
+                     LabelBlock* label_block)
+      : Expression(kKind, pos),
+        try_expression(try_expression),
+        label_block(label_block) {}
+  Expression* try_expression;
+  LabelBlock* label_block;
 };
 
 struct BlockStatement : Statement {

src/torque/declaration-visitor.cc

@@ -402,14 +402,15 @@ void DeclarationVisitor::Visit(ForLoopStatement* stmt) {
   if (stmt->action) Visit(*stmt->action);
 }
 
-void DeclarationVisitor::Visit(TryLabelStatement* stmt) {
-  // Activate a new scope to declare handler labels, they should not be
-  // visible outside the label block.
+void DeclarationVisitor::Visit(TryLabelExpression* stmt) {
+  // Activate a new scope to declare the handler's label parameters, they should
+  // not be visible outside the label block.
   {
     Declarations::NodeScopeActivator scope(declarations(), stmt);
 
-    // Declare labels
-    for (LabelBlock* block : stmt->label_blocks) {
+    // Declare label
+    {
+      LabelBlock* block = stmt->label_block;
       CurrentSourcePosition::Scope scope(block->pos);
       Label* shared_label =
           declarations()->DeclareLabel(block->label, block->body);
@@ -432,18 +433,16 @@ void DeclarationVisitor::Visit(TryLabelStatement* stmt) {
           shared_label->AddVariable(DeclareVariable(p, type, false));
           ++i;
         }
-      }
-      if (global_context_.verbose()) {
-        std::cout << " declaring label " << block->label << "\n";
+        if (global_context_.verbose()) {
+          std::cout << " declaring label " << block->label << "\n";
+        }
       }
     }
 
-    Visit(stmt->try_block);
+    Visit(stmt->try_expression);
   }
 
-  for (LabelBlock* block : stmt->label_blocks) {
-    Visit(block->body);
-  }
+  Visit(stmt->label_block->body);
 }
 
 void DeclarationVisitor::GenerateHeader(std::string& file_name) {
@@ -516,6 +515,10 @@ void DeclarationVisitor::Visit(IdentifierExpression* expr) {
   }
 }
 
+void DeclarationVisitor::Visit(StatementExpression* expr) {
+  Visit(expr->statement);
+}
+
 void DeclarationVisitor::Visit(CallExpression* expr) {
   Visit(&expr->callee);
   for (Expression* arg : expr->arguments) Visit(arg);

src/torque/declaration-visitor.h

@@ -139,7 +139,8 @@ class DeclarationVisitor : public FileVisitor {
 
   void Visit(AssumeTypeImpossibleExpression* expr) { Visit(expr->expression); }
 
-  void Visit(TryLabelStatement* stmt);
+  void Visit(TryLabelExpression* stmt);
+  void Visit(StatementExpression* stmt);
   void GenerateHeader(std::string& file_name);
 
  private:

src/torque/implementation-visitor.cc

@@ -80,6 +80,7 @@ void ImplementationVisitor::BeginModuleFile(Module* module) {
                   DashifyString(module->name()) + "-gen.h\"";
   }
   source << "\n";
+  source << "#include \"src/objects/arguments.h\"\n";
   source << "#include \"src/builtins/builtins-utils-gen.h\"\n";
   source << "#include \"src/builtins/builtins.h\"\n";
   source << "#include \"src/code-factory.h\"\n";
@@ -1081,19 +1082,19 @@ const Type* ImplementationVisitor::Visit(ForOfLoopStatement* stmt) {
   return TypeOracle::GetVoidType();
 }
 
-const Type* ImplementationVisitor::Visit(TryLabelStatement* stmt) {
+VisitResult ImplementationVisitor::Visit(TryLabelExpression* expr) {
   Block* done_block = assembler().NewBlock();
-  const Type* try_result = TypeOracle::GetNeverType();
-  std::vector<Label*> labels;
+  VisitResult try_result;
+  Label* label = nullptr;
 
   // Output labels for the goto handlers and for the merge after the try.
   {
     // Activate a new scope to see handler labels
-    Declarations::NodeScopeActivator scope(declarations(), stmt);
-    for (LabelBlock* block : stmt->label_blocks) {
+    Declarations::NodeScopeActivator scope(declarations(), expr);
+    {
+      LabelBlock* block = expr->label_block;
       CurrentSourcePosition::Scope source_position(block->pos);
-      Label* label = declarations()->LookupLabel(block->label);
-      labels.push_back(label);
+      label = declarations()->LookupLabel(block->label);
 
       Declarations::NodeScopeActivator scope(declarations(), block->body);
       Stack<const Type*> label_input_stack = assembler().CurrentStack();
@@ -1108,42 +1109,48 @@ const Type* ImplementationVisitor::Visit(TryLabelStatement* stmt) {
     // Visit try
     {
       StackScope stack_scope(this);
-      try_result = Visit(stmt->try_block);
-    }
-    if (try_result != TypeOracle::GetNeverType()) {
-      assembler().Goto(done_block);
+      try_result = Visit(expr->try_expression);
+      if (try_result.type() != TypeOracle::GetNeverType()) {
+        try_result = stack_scope.Yield(try_result);
+        assembler().Goto(done_block);
+      }
     }
   }
 
-  // Make sure that each label clause is actually used. It's not just a friendly
-  // thing to do, it will cause problems downstream in the compiler if there are
-  // bound labels that are never jumped to.
-  auto label_iterator = stmt->label_blocks.begin();
-  for (auto label : labels) {
-    CurrentSourcePosition::Scope scope((*label_iterator)->pos);
-    if (!label->IsUsed()) {
-      std::stringstream s;
-      s << "label ";
-      s << (*label_iterator)->label;
-      s << " has a handler block but is never referred to in try block";
-      ReportError(s.str());
+  if (label->IsUsed()) {
+    // Visit and output the code for the label block. If the label block falls
+    // through, then the try must not return a value. Also, if the try doesn't
+    // fall through, but the label does, then overall the try-label block
+    // returns type void.
+    GenerateLabelBind(label);
+    const Type* label_result;
+    {
+      StackScope stack_scope(this);
+      label_result = Visit(expr->label_block->body);
+    }
+    if (!try_result.type()->IsVoidOrNever() && label_result->IsVoid()) {
+      ReportError(
+          "otherwise clauses cannot fall through in a non-void expression");
+    }
+    if (label_result != TypeOracle::GetNeverType()) {
+      assembler().Goto(done_block);
+    }
+    if (label_result->IsVoid() && try_result.type()->IsNever()) {
+      try_result =
+          VisitResult(TypeOracle::GetVoidType(), try_result.stack_range());
     }
-    label_iterator++;
-  }
-
-  // Visit and output the code for each label block, one-by-one.
-  std::vector<Statement*> bodies;
-  for (LabelBlock* block : stmt->label_blocks) bodies.push_back(block->body);
-  if (GenerateLabeledStatementBlocks(bodies, labels, done_block)) {
-    try_result = TypeOracle::GetVoidType();
   }
 
-  if (!try_result->IsNever()) {
+  if (!try_result.type()->IsNever()) {
     assembler().Bind(done_block);
   }
   return try_result;
 }
 
+VisitResult ImplementationVisitor::Visit(StatementExpression* expr) {
+  return VisitResult{Visit(expr->statement), assembler().TopRange(0)};
+}
+
 const Type* ImplementationVisitor::Visit(BreakStatement* stmt) {
   Block* break_block = global_context_.GetCurrentBreak();
   if (break_block == nullptr) {

src/torque/implementation-visitor.h

@@ -177,8 +177,9 @@ class ImplementationVisitor : public FileVisitor {
   VisitResult Visit(StringLiteralExpression* expr);
   VisitResult Visit(NumberLiteralExpression* expr);
   VisitResult Visit(AssumeTypeImpossibleExpression* expr);
+  VisitResult Visit(TryLabelExpression* expr);
+  VisitResult Visit(StatementExpression* expr);
 
-  const Type* Visit(TryLabelStatement* stmt);
   const Type* Visit(ReturnStatement* stmt);
   const Type* Visit(GotoStatement* stmt);
   const Type* Visit(IfStatement* stmt);

src/torque/torque-parser.cc

@@ -201,14 +201,50 @@ void CheckNotDeferredStatement(Statement* statement) {
   }
 }
 
+Expression* MakeCall(const std::string& callee, bool is_operator,
+                     const std::vector<TypeExpression*>& generic_arguments,
+                     const std::vector<Expression*>& arguments,
+                     const std::vector<Statement*>& otherwise) {
+  std::vector<std::string> labels;
+
+  // All IdentifierExpressions are treated as label names and can be directly
+  // used as labels identifiers. All other statements in a call's otherwise
+  // must create intermediate Labels for the otherwise's statement code.
+  size_t label_id = 0;
+  std::vector<LabelBlock*> temp_labels;
+  for (auto* statement : otherwise) {
+    if (auto* e = ExpressionStatement::DynamicCast(statement)) {
+      if (auto* id = IdentifierExpression::DynamicCast(e->expression)) {
+        if (id->generic_arguments.size() != 0) {
+          ReportError("An otherwise label cannot have generic parameters");
+        }
+        labels.push_back(id->name);
+        continue;
+      }
+    }
+    auto label_name = std::string("_label") + std::to_string(label_id++);
+    labels.push_back(label_name);
+    auto* label_block =
+        MakeNode<LabelBlock>(label_name, ParameterList::Empty(), statement);
+    temp_labels.push_back(label_block);
+  }
+
+  // Create nested try-label expression for all of the temporary Labels that
+  // were created.
+  Expression* result = MakeNode<CallExpression>(
+      callee, false, generic_arguments, arguments, labels);
+  for (auto* label : temp_labels) {
+    result = MakeNode<TryLabelExpression>(result, label);
+  }
+  return result;
+}
+
 base::Optional<ParseResult> MakeCall(ParseResultIterator* child_results) {
   auto callee = child_results->NextAs<std::string>();
   auto generic_args = child_results->NextAs<TypeList>();
   auto args = child_results->NextAs<std::vector<Expression*>>();
-  auto labels = child_results->NextAs<std::vector<std::string>>();
-  Expression* result =
-      MakeNode<CallExpression>(callee, false, generic_args, args, labels);
-  return ParseResult{result};
+  auto otherwise = child_results->NextAs<std::vector<Statement*>>();
+  return ParseResult{MakeCall(callee, false, generic_args, args, otherwise)};
 }
 
 base::Optional<ParseResult> MakeBinaryOperator(
@@ -216,20 +252,17 @@ base::Optional<ParseResult> MakeBinaryOperator(
   auto left = child_results->NextAs<Expression*>();
   auto op = child_results->NextAs<std::string>();
   auto right = child_results->NextAs<Expression*>();
-  Expression* result = MakeNode<CallExpression>(
-      op, true, TypeList{}, std::vector<Expression*>{left, right},
-      std::vector<std::string>{});
-  return ParseResult{result};
+  return ParseResult{MakeCall(op, true, TypeList{},
+                              std::vector<Expression*>{left, right},
+                              std::vector<Statement*>{})};
 }
 
 base::Optional<ParseResult> MakeUnaryOperator(
     ParseResultIterator* child_results) {
   auto op = child_results->NextAs<std::string>();
   auto e = child_results->NextAs<Expression*>();
-  Expression* result = MakeNode<CallExpression>(op, true, TypeList{},
-                                                std::vector<Expression*>{e},
-                                                std::vector<std::string>{});
-  return ParseResult{result};
+  return ParseResult{MakeCall(op, true, TypeList{}, std::vector<Expression*>{e},
+                              std::vector<Statement*>{})};
 }
 
 template <bool has_varargs>
@@ -584,10 +617,11 @@ base::Optional<ParseResult> MakeTypeswitchStatement(
     }
     BlockStatement* case_block;
     if (i < cases.size() - 1) {
-      value = MakeNode<CallExpression>(
-          "Cast", false, std::vector<TypeExpression*>{cases[i].type},
-          std::vector<Expression*>{value},
-          std::vector<std::string>{"_NextCase"});
+      value =
+          MakeCall("Cast", false, std::vector<TypeExpression*>{cases[i].type},
+                   std::vector<Expression*>{value},
+                   std::vector<Statement*>{MakeNode<ExpressionStatement>(
+                       MakeNode<IdentifierExpression>("_NextCase"))});
       case_block = MakeNode<BlockStatement>();
     } else {
       case_block = current_block;
@@ -599,9 +633,11 @@ base::Optional<ParseResult> MakeTypeswitchStatement(
     case_block->statements.push_back(cases[i].block);
     if (i < cases.size() - 1) {
       BlockStatement* next_block = MakeNode<BlockStatement>();
-      current_block->statements.push_back(MakeNode<TryLabelStatement>(
-          case_block, std::vector<LabelBlock*>{MakeNode<LabelBlock>(
-                          "_NextCase", ParameterList::Empty(), next_block)}));
+      current_block->statements.push_back(
+          MakeNode<ExpressionStatement>(MakeNode<TryLabelExpression>(
+              MakeNode<StatementExpression>(case_block),
+              MakeNode<LabelBlock>("_NextCase", ParameterList::Empty(),
+                                   next_block))));
       current_block = next_block;
     }
     accumulated_types =
@@ -692,13 +728,16 @@ base::Optional<ParseResult> MakeBlockStatement(
   return ParseResult{result};
 }
 
-base::Optional<ParseResult> MakeTryLabelStatement(
+base::Optional<ParseResult> MakeTryLabelExpression(
     ParseResultIterator* child_results) {
   auto try_block = child_results->NextAs<Statement*>();
   CheckNotDeferredStatement(try_block);
+  Statement* result = try_block;
   auto label_blocks = child_results->NextAs<std::vector<LabelBlock*>>();
-  Statement* result =
-      MakeNode<TryLabelStatement>(try_block, std::move(label_blocks));
+  for (auto block : label_blocks) {
+    result = MakeNode<ExpressionStatement>(MakeNode<TryLabelExpression>(
+        MakeNode<StatementExpression>(result), block));
+  }
   return ParseResult{result};
 }
 
@@ -1028,10 +1067,10 @@ struct TorqueGrammar : Grammar {
       Sequence({Token("labels"),
                 NonemptyList<LabelAndTypes>(&labelParameter, Token(","))}))};
 
-  // Result: std::vector<std::string>
-  Symbol* optionalOtherwise{TryOrDefault<std::vector<std::string>>(
+  // Result: std::vector<Statement*>
+  Symbol* optionalOtherwise{TryOrDefault<std::vector<Statement*>>(
       Sequence({Token("otherwise"),
-                NonemptyList<std::string>(&identifier, Token(","))}))};
+                NonemptyList<Statement*>(&atomarStatement, Token(","))}))};
 
   // Result: NameAndTypeExpression
   Symbol nameAndType = {
@@ -1212,28 +1251,27 @@ struct TorqueGrammar : Grammar {
             expression},
            MakeVarDeclarationStatement)};
 
-  // Disallow ambiguous dangling else by only allowing an {atomarStatement} as
-  // a then-clause. Result: Statement*
+  // Result: Statement*
   Symbol atomarStatement = {
-      Rule({&block}),
-      Rule({expression, Token(";")}, MakeExpressionStatement),
-      Rule({Token("return"), Optional<Expression*>(expression), Token(";")},
+      Rule({expression}, MakeExpressionStatement),
+      Rule({Token("return"), Optional<Expression*>(expression)},
            MakeReturnStatement),
-      Rule({Token("tail"), &callExpression, Token(";")}, MakeTailCallStatement),
-      Rule({Token("break"), Token(";")}, MakeBreakStatement),
-      Rule({Token("continue"), Token(";")}, MakeContinueStatement),
+      Rule({Token("tail"), &callExpression}, MakeTailCallStatement),
+      Rule({Token("break")}, MakeBreakStatement),
+      Rule({Token("continue")}, MakeContinueStatement),
       Rule({Token("goto"), &identifier,
-            TryOrDefault<std::vector<Expression*>>(&argumentList), Token(";")},
+            TryOrDefault<std::vector<Expression*>>(&argumentList)},
            MakeGotoStatement),
-      Rule({OneOf({"debug", "unreachable"}), Token(";")}, MakeDebugStatement)};
+      Rule({OneOf({"debug", "unreachable"})}, MakeDebugStatement)};
 
   // Result: Statement*
   Symbol statement = {
-      Rule({&atomarStatement}),
+      Rule({&block}),
+      Rule({&atomarStatement, Token(";")}),
       Rule({&varDeclaration, Token(";")}),
       Rule({&varDeclarationWithInitialization, Token(";")}),
       Rule({Token("if"), CheckIf(Token("constexpr")), Token("("), expression,
-            Token(")"), &atomarStatement,
+            Token(")"), &statement,
             Optional<Statement*>(Sequence({Token("else"), &statement}))},
            MakeIfStatement),
       Rule(
@@ -1244,21 +1282,19 @@ struct TorqueGrammar : Grammar {
           },
           MakeTypeswitchStatement),
       Rule({Token("try"), &block, NonemptyList<LabelBlock*>(&labelBlock)},
-           MakeTryLabelStatement),
+           MakeTryLabelExpression),
       Rule({OneOf({"assert", "check"}), Token("("), &expressionWithSource,
             Token(")"), Token(";")},
            MakeAssertStatement),
-      Rule({Token("while"), Token("("), expression, Token(")"),
-            &atomarStatement},
+      Rule({Token("while"), Token("("), expression, Token(")"), &statement},
            MakeWhileStatement),
       Rule({Token("for"), Token("("), &varDeclaration, Token("of"), expression,
-            Optional<RangeExpression>(&rangeSpecifier), Token(")"),
-            &atomarStatement},
+            Optional<RangeExpression>(&rangeSpecifier), Token(")"), &statement},
            MakeForOfLoopStatement),
       Rule({Token("for"), Token("("),
             Optional<Statement*>(&varDeclarationWithInitialization), Token(";"),
             Optional<Expression*>(expression), Token(";"),
-            Optional<Expression*>(expression), Token(")"), &atomarStatement},
+            Optional<Expression*>(expression), Token(")"), &statement},
            MakeForLoopStatement)};
 
   // Result: TypeswitchCase

test/cctest/torque/test-torque.cc

@@ -271,6 +271,21 @@ TEST(TestLogicalOperators) {
   ft.Call();
 }
 
+TEST(TestOtherwiseAndLabels) {
+  Isolate* isolate(CcTest::InitIsolateOnce());
+  CodeAssemblerTester asm_tester(isolate, 0);
+  TestBuiltinsFromDSLAssembler m(asm_tester.state());
+  {
+    m.TestOtherwiseWithCode1();
+    m.TestOtherwiseWithCode2();
+    m.TestOtherwiseWithCode3();
+    m.TestForwardLabel();
+    m.Return(m.UndefinedConstant());
+  }
+  FunctionTester ft(asm_tester.GenerateCode(), 0);
+  ft.Call();
+}
+
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8

test/torque/test-torque.tq

@@ -154,9 +154,9 @@ module test {
       check(GenericMacroTest<Object>(Null) == Null);
       check(GenericMacroTest<Object>(False) == False);
       check(GenericMacroTest<Object>(True) == True);
-      check(GenericMacroTestWithLabels<Smi>(0) otherwise Fail == Undefined);
-      check(GenericMacroTestWithLabels<Smi>(0) otherwise Fail == Undefined);
-      check(GenericMacroTestWithLabels<Object>(smi0) otherwise Fail == smi0);
+      check((GenericMacroTestWithLabels<Smi>(0) otherwise Fail) == Undefined);
+      check((GenericMacroTestWithLabels<Smi>(0) otherwise Fail) == Undefined);
+      check((GenericMacroTestWithLabels<Object>(smi0) otherwise Fail) == smi0);
       try {
         GenericMacroTestWithLabels<Object>(False) otherwise Expected;
       }
@@ -541,4 +541,51 @@ module test {
     check(!TestOrAnd2(false, false, false));
     check(!TestOrAnd3(false, false, false));
   }
+
+  macro TestCall(i: Smi): Smi
+      labels A {
+    if (i < 5) return i;
+    goto A;
+  }
+
+  macro TestOtherwiseWithCode1() {
+    let v: Smi = 0;
+    let s: Smi = 1;
+    try {
+      TestCall(10) otherwise goto B(++s);
+    }
+    label B(v1: Smi) {
+      v = v1;
+    }
+    assert(v == 2);
+  }
+
+  macro TestOtherwiseWithCode2() {
+    let s: Smi = 0;
+    for (let i: Smi = 0; i < 10; ++i) {
+      TestCall(i) otherwise break;
+      ++s;
+    }
+    assert(s == 5);
+  }
+
+  macro TestOtherwiseWithCode3() {
+    let s: Smi = 0;
+    for (let i: Smi = 0; i < 10; ++i) {
+      s += TestCall(i) otherwise break;
+    }
+    assert(s == 10);
+  }
+
+  macro TestForwardLabel() {
+    try {
+      goto A;
+    }
+    label A {
+      goto B(5);
+    }
+    label B(b: Smi) {
+      assert(b == 5);
+    }
+  }
 }