LibJS: Remove hand-rolled type information in JS AST in favor of RTTI

Libraries/LibJS/AST.cpp

@@ -130,21 +130,21 @@ CallExpression::ThisAndCallee CallExpression::compute_this_and_callee(Interprete
 {
     auto& vm = interpreter.vm();
 
-    if (is_new_expression()) {
+    if (is<NewExpression>(*this)) {
         // Computing |this| is irrelevant for "new" expression.
         return { js_undefined(), m_callee->execute(interpreter, global_object) };
     }
 
-    if (m_callee->is_super_expression()) {
+    if (is<SuperExpression>(*m_callee)) {
         // If we are calling super, |this| has not been initialized yet, and would not be meaningful to provide.
         auto new_target = vm.get_new_target();
         ASSERT(new_target.is_function());
         return { js_undefined(), new_target };
     }
 
-    if (m_callee->is_member_expression()) {
+    if (is<MemberExpression>(*m_callee)) {
         auto& member_expression = static_cast<const MemberExpression&>(*m_callee);
-        bool is_super_property_lookup = member_expression.object().is_super_expression();
+        bool is_super_property_lookup = is<SuperExpression>(member_expression.object());
         auto lookup_target = is_super_property_lookup ? interpreter.current_environment()->get_super_base() : member_expression.object().execute(interpreter, global_object);
         if (vm.exception())
             return {};
@@ -178,12 +178,12 @@ Value CallExpression::execute(Interpreter& interpreter, GlobalObject& global_obj
     ASSERT(!callee.is_empty());
 
     if (!callee.is_function()
-        || (is_new_expression() && (is<NativeFunction>(callee.as_object()) && !static_cast<NativeFunction&>(callee.as_object()).has_constructor()))) {
+        || (is<NewExpression>(*this) && (is<NativeFunction>(callee.as_object()) && !static_cast<NativeFunction&>(callee.as_object()).has_constructor()))) {
         String error_message;
-        auto call_type = is_new_expression() ? "constructor" : "function";
-        if (m_callee->is_identifier() || m_callee->is_member_expression()) {
+        auto call_type = is<NewExpression>(*this) ? "constructor" : "function";
+        if (is<Identifier>(*m_callee) || is<MemberExpression>(*m_callee)) {
             String expression_string;
-            if (m_callee->is_identifier()) {
+            if (is<Identifier>(*m_callee)) {
                 expression_string = static_cast<const Identifier&>(*m_callee).string();
             } else {
                 expression_string = static_cast<const MemberExpression&>(*m_callee).to_string_approximation();
@@ -220,11 +220,11 @@ Value CallExpression::execute(Interpreter& interpreter, GlobalObject& global_obj
 
     Object* new_object = nullptr;
     Value result;
-    if (is_new_expression()) {
+    if (is<NewExpression>(*this)) {
         result = vm.construct(function, function, move(arguments), global_object);
         if (result.is_object())
             new_object = &result.as_object();
-    } else if (m_callee->is_super_expression()) {
+    } else if (is<SuperExpression>(*m_callee)) {
         auto* super_constructor = interpreter.current_environment()->current_function()->prototype();
         // FIXME: Functions should track their constructor kind.
         if (!super_constructor || !super_constructor->is_function()) {
@@ -243,7 +243,7 @@ Value CallExpression::execute(Interpreter& interpreter, GlobalObject& global_obj
     if (vm.exception())
         return {};
 
-    if (is_new_expression()) {
+    if (is<NewExpression>(*this)) {
         if (result.is_object())
             return result;
         return new_object;
@@ -371,7 +371,7 @@ Value ForStatement::execute(Interpreter& interpreter, GlobalObject& global_objec
 
     RefPtr<BlockStatement> wrapper;
 
-    if (m_init && m_init->is_variable_declaration() && static_cast<const VariableDeclaration*>(m_init.ptr())->declaration_kind() != DeclarationKind::Var) {
+    if (m_init && is<VariableDeclaration>(*m_init) && static_cast<const VariableDeclaration&>(*m_init).declaration_kind() != DeclarationKind::Var) {
         wrapper = create_ast_node<BlockStatement>(source_range());
         NonnullRefPtrVector<VariableDeclaration> decls;
         decls.append(*static_cast<const VariableDeclaration*>(m_init.ptr()));
@@ -444,20 +444,20 @@ Value ForStatement::execute(Interpreter& interpreter, GlobalObject& global_objec
     return last_value;
 }
 
-static FlyString variable_from_for_declaration(Interpreter& interpreter, GlobalObject& global_object, NonnullRefPtr<ASTNode> node, RefPtr<BlockStatement> wrapper)
+static FlyString variable_from_for_declaration(Interpreter& interpreter, GlobalObject& global_object, const ASTNode& node, RefPtr<BlockStatement> wrapper)
 {
     FlyString variable_name;
-    if (node->is_variable_declaration()) {
-        auto* variable_declaration = static_cast<const VariableDeclaration*>(node.ptr());
-        ASSERT(!variable_declaration->declarations().is_empty());
-        if (variable_declaration->declaration_kind() != DeclarationKind::Var) {
-            wrapper = create_ast_node<BlockStatement>(node->source_range());
+    if (is<VariableDeclaration>(node)) {
+        auto& variable_declaration = static_cast<const VariableDeclaration&>(node);
+        ASSERT(!variable_declaration.declarations().is_empty());
+        if (variable_declaration.declaration_kind() != DeclarationKind::Var) {
+            wrapper = create_ast_node<BlockStatement>(node.source_range());
             interpreter.enter_scope(*wrapper, ScopeType::Block, global_object);
         }
-        variable_declaration->execute(interpreter, global_object);
-        variable_name = variable_declaration->declarations().first().id().string();
-    } else if (node->is_identifier()) {
-        variable_name = static_cast<const Identifier&>(*node).string();
+        variable_declaration.execute(interpreter, global_object);
+        variable_name = variable_declaration.declarations().first().id().string();
+    } else if (is<Identifier>(node)) {
+        variable_name = static_cast<const Identifier&>(node).string();
     } else {
         ASSERT_NOT_REACHED();
     }
@@ -469,7 +469,7 @@ Value ForInStatement::execute(Interpreter& interpreter, GlobalObject& global_obj
     interpreter.enter_node(*this);
     ScopeGuard exit_node { [&] { interpreter.exit_node(*this); } };
 
-    if (!m_lhs->is_variable_declaration() && !m_lhs->is_identifier()) {
+    if (!is<VariableDeclaration>(*m_lhs) && !is<Identifier>(*m_lhs)) {
         // FIXME: Implement "for (foo.bar in baz)", "for (foo[0] in bar)"
         ASSERT_NOT_REACHED();
     }
@@ -516,7 +516,7 @@ Value ForOfStatement::execute(Interpreter& interpreter, GlobalObject& global_obj
     interpreter.enter_node(*this);
     ScopeGuard exit_node { [&] { interpreter.exit_node(*this); } };
 
-    if (!m_lhs->is_variable_declaration() && !m_lhs->is_identifier()) {
+    if (!is<VariableDeclaration>(*m_lhs) && !is<Identifier>(*m_lhs)) {
         // FIXME: Implement "for (foo.bar of baz)", "for (foo[0] of bar)"
         ASSERT_NOT_REACHED();
     }
@@ -700,7 +700,7 @@ Value UnaryExpression::execute(Interpreter& interpreter, GlobalObject& global_ob
     }
 
     Value lhs_result;
-    if (m_op == UnaryOp::Typeof && m_lhs->is_identifier()) {
+    if (m_op == UnaryOp::Typeof && is<Identifier>(*m_lhs)) {
         auto reference = m_lhs->to_reference(interpreter, global_object);
         if (interpreter.exception()) {
             return {};
@@ -1052,7 +1052,7 @@ void UnaryExpression::dump(int indent) const
 void CallExpression::dump(int indent) const
 {
     print_indent(indent);
-    if (is_new_expression())
+    if (is<NewExpression>(*this))
         outln("CallExpression [new]");
     else
         outln("CallExpression");
@@ -1744,7 +1744,7 @@ void MemberExpression::dump(int indent) const
 PropertyName MemberExpression::computed_property_name(Interpreter& interpreter, GlobalObject& global_object) const
 {
     if (!is_computed()) {
-        ASSERT(m_property->is_identifier());
+        ASSERT(is<Identifier>(*m_property));
         return static_cast<const Identifier&>(*m_property).string();
     }
     auto value = m_property->execute(interpreter, global_object);
@@ -1757,11 +1757,11 @@ PropertyName MemberExpression::computed_property_name(Interpreter& interpreter,
 String MemberExpression::to_string_approximation() const
 {
     String object_string = "<object>";
-    if (m_object->is_identifier())
+    if (is<Identifier>(*m_object))
         object_string = static_cast<const Identifier&>(*m_object).string();
     if (is_computed())
         return String::formatted("{}[<computed>]", object_string);
-    ASSERT(m_property->is_identifier());
+    ASSERT(is<Identifier>(*m_property));
     return String::formatted("{}.{}", object_string, static_cast<const Identifier&>(*m_property).string());
 }
 
@@ -1887,7 +1887,7 @@ Value ArrayExpression::execute(Interpreter& interpreter, GlobalObject& global_ob
             if (interpreter.exception())
                 return {};
 
-            if (element->is_spread_expression()) {
+            if (is<SpreadExpression>(*element)) {
                 get_iterator_values(global_object, value, [&](Value iterator_value) {
                     array->indexed_properties().append(iterator_value);
                     return IterationDecision::Continue;

Libraries/LibJS/AST.h

@@ -56,17 +56,6 @@ public:
     virtual const char* class_name() const = 0;
     virtual Value execute(Interpreter&, GlobalObject&) const = 0;
     virtual void dump(int indent) const;
-    virtual bool is_identifier() const { return false; }
-    virtual bool is_spread_expression() const { return false; }
-    virtual bool is_member_expression() const { return false; }
-    virtual bool is_scope_node() const { return false; }
-    virtual bool is_program() const { return false; }
-    virtual bool is_variable_declaration() const { return false; }
-    virtual bool is_call_expression() const { return false; }
-    virtual bool is_new_expression() const { return false; }
-    virtual bool is_super_expression() const { return false; }
-    virtual bool is_expression_statement() const { return false; };
-    virtual bool is_string_literal() const { return false; };
 
     const SourceRange& source_range() const { return m_source_range; }
     SourceRange& source_range() { return m_source_range; }
@@ -125,7 +114,6 @@ public:
 
     virtual Value execute(Interpreter&, GlobalObject&) const override;
     virtual void dump(int indent) const override;
-    virtual bool is_expression_statement() const override { return true; }
 
     const Expression& expression() const { return m_expression; };
 
@@ -165,7 +153,6 @@ protected:
     }
 
 private:
-    virtual bool is_scope_node() const final { return true; }
     NonnullRefPtrVector<Statement> m_children;
     NonnullRefPtrVector<VariableDeclaration> m_variables;
     NonnullRefPtrVector<FunctionDeclaration> m_functions;
@@ -186,7 +173,6 @@ public:
 private:
     bool m_is_strict_mode { false };
 
-    virtual bool is_program() const override { return true; }
     virtual const char* class_name() const override { return "Program"; }
 };
 
@@ -695,7 +681,6 @@ public:
 
     virtual Value execute(Interpreter&, GlobalObject&) const override;
     virtual void dump(int indent) const override;
-    virtual bool is_string_literal() const override { return true; };
 
     StringView value() const { return m_value; }
     bool is_use_strict_directive() const { return m_is_use_strict_directive; };
@@ -755,7 +740,6 @@ public:
 
     virtual Value execute(Interpreter&, GlobalObject&) const override;
     virtual void dump(int indent) const override;
-    virtual bool is_identifier() const override { return true; }
     virtual Reference to_reference(Interpreter&, GlobalObject&) const override;
 
 private:
@@ -808,7 +792,6 @@ public:
     virtual void dump(int indent) const override;
 
 private:
-    virtual bool is_super_expression() const override { return true; }
     virtual const char* class_name() const override { return "SuperExpression"; }
 };
 
@@ -863,7 +846,6 @@ public:
 
     virtual Value execute(Interpreter&, GlobalObject&) const override;
     virtual void dump(int indent) const override;
-    virtual bool is_spread_expression() const override { return true; }
 
 private:
     virtual const char* class_name() const override { return "SpreadExpression"; }
@@ -903,7 +885,6 @@ public:
 
 private:
     virtual const char* class_name() const override { return "CallExpression"; }
-    virtual bool is_call_expression() const override { return true; }
 
     struct ThisAndCallee {
         Value this_value;
@@ -924,8 +905,6 @@ public:
 
 private:
     virtual const char* class_name() const override { return "NewExpression"; }
-    virtual bool is_call_expression() const override { return false; }
-    virtual bool is_new_expression() const override { return true; }
 };
 
 enum class AssignmentOp {
@@ -1037,7 +1016,6 @@ public:
     {
     }
 
-    virtual bool is_variable_declaration() const override { return true; }
     DeclarationKind declaration_kind() const { return m_declaration_kind; }
 
     virtual Value execute(Interpreter&, GlobalObject&) const override;
@@ -1198,7 +1176,6 @@ public:
     String to_string_approximation() const;
 
 private:
-    virtual bool is_member_expression() const override { return true; }
     virtual const char* class_name() const override { return "MemberExpression"; }
 
     NonnullRefPtr<Expression> m_object;

Libraries/LibJS/Interpreter.cpp

@@ -107,7 +107,7 @@ void Interpreter::enter_scope(const ScopeNode& scope_node, ScopeType scope_type,
 
     for (auto& declaration : scope_node.variables()) {
         for (auto& declarator : declaration.declarations()) {
-            if (scope_node.is_program()) {
+            if (is<Program>(scope_node)) {
                 global_object.put(declarator.id().string(), js_undefined());
                 if (exception())
                     return;
@@ -160,7 +160,7 @@ void Interpreter::push_scope(ScopeFrame frame)
 
 Value Interpreter::execute_statement(GlobalObject& global_object, const Statement& statement, ScopeType scope_type)
 {
-    if (!statement.is_scope_node())
+    if (!is<ScopeNode>(statement))
         return statement.execute(*this, global_object);
 
     auto& block = static_cast<const ScopeNode&>(statement);

Libraries/LibJS/Parser.cpp

@@ -35,11 +35,11 @@ namespace JS {
 
 static bool statement_is_use_strict_directive(NonnullRefPtr<Statement> statement)
 {
-    if (!statement->is_expression_statement())
+    if (!is<ExpressionStatement>(*statement))
         return false;
     auto& expression_statement = static_cast<ExpressionStatement&>(*statement);
     auto& expression = expression_statement.expression();
-    if (!expression.is_string_literal())
+    if (!is<StringLiteral>(expression))
         return false;
     return static_cast<const StringLiteral&>(expression).is_use_strict_directive();
 }
@@ -711,7 +711,7 @@ NonnullRefPtr<Expression> Parser::parse_unary_prefixed_expression()
         auto rhs = parse_expression(precedence, associativity);
         // FIXME: Apparently for functions this should also not be enforced on a parser level,
         // other engines throw ReferenceError for ++foo()
-        if (!rhs->is_identifier() && !rhs->is_member_expression())
+        if (!is<Identifier>(*rhs) && !is<MemberExpression>(*rhs))
             syntax_error(String::formatted("Right-hand side of prefix increment operator must be identifier or member expression, got {}", rhs->class_name()), rhs_start);
         return create_ast_node<UpdateExpression>({ rule_start.position(), position() }, UpdateOp::Increment, move(rhs), true);
     }
@@ -721,7 +721,7 @@ NonnullRefPtr<Expression> Parser::parse_unary_prefixed_expression()
         auto rhs = parse_expression(precedence, associativity);
         // FIXME: Apparently for functions this should also not be enforced on a parser level,
         // other engines throw ReferenceError for --foo()
-        if (!rhs->is_identifier() && !rhs->is_member_expression())
+        if (!is<Identifier>(*rhs) && !is<MemberExpression>(*rhs))
             syntax_error(String::formatted("Right-hand side of prefix decrement operator must be identifier or member expression, got {}", rhs->class_name()), rhs_start);
         return create_ast_node<UpdateExpression>({ rule_start.position(), position() }, UpdateOp::Decrement, move(rhs), true);
     }
@@ -1120,14 +1120,14 @@ NonnullRefPtr<Expression> Parser::parse_secondary_expression(NonnullRefPtr<Expre
     case TokenType::PlusPlus:
         // FIXME: Apparently for functions this should also not be enforced on a parser level,
         // other engines throw ReferenceError for foo()++
-        if (!lhs->is_identifier() && !lhs->is_member_expression())
+        if (!is<Identifier>(*lhs) && !is<MemberExpression>(*lhs))
             syntax_error(String::formatted("Left-hand side of postfix increment operator must be identifier or member expression, got {}", lhs->class_name()));
         consume();
         return create_ast_node<UpdateExpression>({ rule_start.position(), position() }, UpdateOp::Increment, move(lhs));
     case TokenType::MinusMinus:
         // FIXME: Apparently for functions this should also not be enforced on a parser level,
         // other engines throw ReferenceError for foo()--
-        if (!lhs->is_identifier() && !lhs->is_member_expression())
+        if (!is<Identifier>(*lhs) && !is<MemberExpression>(*lhs))
             syntax_error(String::formatted("Left-hand side of postfix increment operator must be identifier or member expression, got {}", lhs->class_name()));
         consume();
         return create_ast_node<UpdateExpression>({ rule_start.position(), position() }, UpdateOp::Decrement, move(lhs));
@@ -1175,13 +1175,13 @@ NonnullRefPtr<AssignmentExpression> Parser::parse_assignment_expression(Assignme
         || match(TokenType::DoublePipeEquals)
         || match(TokenType::DoubleQuestionMarkEquals));
     consume();
-    if (!lhs->is_identifier() && !lhs->is_member_expression() && !lhs->is_call_expression()) {
+    if (!is<Identifier>(*lhs) && !is<MemberExpression>(*lhs) && !is<CallExpression>(*lhs)) {
         syntax_error("Invalid left-hand side in assignment");
-    } else if (m_parser_state.m_strict_mode && lhs->is_identifier()) {
+    } else if (m_parser_state.m_strict_mode && is<Identifier>(*lhs)) {
         auto name = static_cast<const Identifier&>(*lhs).string();
         if (name == "eval" || name == "arguments")
             syntax_error(String::formatted("'{}' cannot be assigned to in strict mode code", name));
-    } else if (m_parser_state.m_strict_mode && lhs->is_call_expression()) {
+    } else if (m_parser_state.m_strict_mode && is<CallExpression>(*lhs)) {
         syntax_error("Cannot assign to function call");
     }
     return create_ast_node<AssignmentExpression>({ rule_start.position(), position() }, assignment_op, move(lhs), parse_expression(min_precedence, associativity));
@@ -1190,7 +1190,7 @@ NonnullRefPtr<AssignmentExpression> Parser::parse_assignment_expression(Assignme
 NonnullRefPtr<CallExpression> Parser::parse_call_expression(NonnullRefPtr<Expression> lhs)
 {
     auto rule_start = push_start();
-    if (!m_parser_state.m_allow_super_constructor_call && lhs->is_super_expression())
+    if (!m_parser_state.m_allow_super_constructor_call && is<SuperExpression>(*lhs))
         syntax_error("'super' keyword unexpected here");
 
     consume(TokenType::ParenOpen);
@@ -1777,7 +1777,7 @@ NonnullRefPtr<Statement> Parser::parse_for_statement()
 NonnullRefPtr<Statement> Parser::parse_for_in_of_statement(NonnullRefPtr<ASTNode> lhs)
 {
     auto rule_start = push_start();
-    if (lhs->is_variable_declaration()) {
+    if (is<VariableDeclaration>(*lhs)) {
         auto declarations = static_cast<VariableDeclaration&>(*lhs).declarations();
         if (declarations.size() > 1)
             syntax_error("multiple declarations not allowed in for..in/of");

Libraries/LibJS/Runtime/ScriptFunction.cpp

@@ -94,7 +94,7 @@ LexicalEnvironment* ScriptFunction::create_environment()
         variables.set(parameter.name, { js_undefined(), DeclarationKind::Var });
     }
 
-    if (body().is_scope_node()) {
+    if (is<ScopeNode>(body())) {
         for (auto& declaration : static_cast<const ScopeNode&>(body()).variables()) {
             for (auto& declarator : declaration.declarations()) {
                 variables.set(declarator.id().string(), { js_undefined(), DeclarationKind::Var });