LibJS: Treat yield as an identifier in more non-generator contexts

And disallow some cases where we are in a generator context.

Userland/Libraries/LibJS/Parser.cpp

@@ -831,7 +831,10 @@ Parser::PrimaryExpressionParseResult Parser::parse_primary_expression()
  auto expression = parse_expression(0);
  consume(TokenType::ParenClose);
  if (is<FunctionExpression>(*expression)) {
- static_cast<FunctionExpression&>(*expression).set_cannot_auto_rename();
+ auto& function = static_cast<FunctionExpression&>(*expression);
+ function.set_cannot_auto_rename();
+ if (function.kind() == FunctionKind::Generator && function.name() == "yield"sv)
+ syntax_error("function is not allowed to be called 'yield' in this context", function.source_range().start);
  }
  return { move(expression) };
  }
@@ -1072,7 +1075,7 @@ NonnullRefPtr<ObjectExpression> Parser::parse_object_expression()
  property_type = ObjectProperty::Type::KeyValue;
  property_name = parse_property_key();
  function_kind = FunctionKind ::Generator;
- } else if (match(TokenType::Identifier)) {
+ } else if (match_identifier()) {
  auto identifier = consume().value();
  if (identifier == "get" && match_property_key()) {
  property_type = ObjectProperty::Type::Getter;
@@ -1750,6 +1753,8 @@ NonnullRefPtr<FunctionNodeType> Parser::parse_function_node(u8 parse_options)
 
  check_identifier_name_for_assignment_validity(name);
  }
+ TemporaryChange generator_change(m_state.in_generator_function_context, is_generator);
+
  consume(TokenType::ParenOpen);
  i32 function_length = -1;
  auto parameters = parse_formal_parameters(function_length, parse_options);
@@ -1759,7 +1764,7 @@ NonnullRefPtr<FunctionNodeType> Parser::parse_function_node(u8 parse_options)
  function_length = parameters.size();
 
  TemporaryChange change(m_state.in_function_context, true);
- TemporaryChange generator_change(m_state.in_generator_function_context, m_state.in_generator_function_context || is_generator);
+
  auto old_labels_in_scope = move(m_state.labels_in_scope);
  ScopeGuard guard([&]() {
  m_state.labels_in_scope = move(old_labels_in_scope);
@@ -1775,12 +1780,15 @@ NonnullRefPtr<FunctionNodeType> Parser::parse_function_node(u8 parse_options)
  auto body = parse_block_statement(is_strict, has_binding);
 
  // If the function contains 'use strict' we need to check the parameters (again).
- if (is_strict) {
+ if (is_strict || is_generator) {
  Vector<StringView> parameter_names;
  for (auto& parameter : parameters) {
  parameter.binding.visit(
  [&](FlyString const& parameter_name) {
- check_identifier_name_for_assignment_validity(parameter_name, true);
+ check_identifier_name_for_assignment_validity(parameter_name, is_strict);
+ if (is_generator && parameter_name == "yield"sv)
+ syntax_error("Parameter name 'yield' not allowed in this context");
+
  for (auto& previous_name : parameter_names) {
  if (previous_name == parameter_name) {
  syntax_error(String::formatted("Duplicate parameter '{}' not allowed in strict mode", parameter_name));
@@ -1791,6 +1799,9 @@ NonnullRefPtr<FunctionNodeType> Parser::parse_function_node(u8 parse_options)
  },
  [&](NonnullRefPtr<BindingPattern> const& binding) {
  binding->for_each_bound_name([&](auto& bound_name) {
+ if (is_generator && bound_name == "yield"sv)
+ syntax_error("Parameter name 'yield' not allowed in this context");
+
  for (auto& previous_name : parameter_names) {
  if (previous_name == bound_name) {
  syntax_error(String::formatted("Duplicate parameter '{}' not allowed in strict mode", bound_name));
@@ -1801,7 +1812,7 @@ NonnullRefPtr<FunctionNodeType> Parser::parse_function_node(u8 parse_options)
  });
  });
  }
- check_identifier_name_for_assignment_validity(name, true);
+ check_identifier_name_for_assignment_validity(name, is_strict);
  }
 
  m_state.function_parameters.take_last();
@@ -2404,7 +2415,7 @@ NonnullRefPtr<CatchClause> Parser::parse_catch_clause()
  if (match(TokenType::ParenOpen)) {
  should_expect_parameter = true;
  consume();
- if (match_identifier_name())
+ if (match_identifier_name() && (!match(TokenType::Yield) || !m_state.in_generator_function_context))
  parameter = consume().value();
  else
  pattern_parameter = parse_binding_pattern();
@@ -2722,7 +2733,8 @@ bool Parser::match_variable_declaration() const
 bool Parser::match_identifier() const
 {
  return m_state.current_token.type() == TokenType::Identifier
- || m_state.current_token.type() == TokenType::Let; // See note in Parser::parse_identifier().
+ || (m_state.current_token.type() == TokenType::Let && !m_state.strict_mode)
+ || (m_state.current_token.type() == TokenType::Yield && !m_state.in_generator_function_context && !m_state.strict_mode); // See note in Parser::parse_identifier().
 }
 
 bool Parser::match_identifier_name() const
@@ -2788,6 +2800,12 @@ Token Parser::consume_identifier()
  return consume();
  }
 
+ if (match(TokenType::Yield)) {
+ if (m_state.strict_mode || m_state.in_generator_function_context)
+ syntax_error("Identifier must not be a reserved word in strict mode ('yield')");
+ return consume();
+ }
+
  expected("Identifier");
  return consume();
 }
@@ -2910,7 +2928,7 @@ void Parser::check_identifier_name_for_assignment_validity(StringView name, bool
  if (name.is_one_of("arguments"sv, "eval"sv))
  syntax_error("Binding pattern target may not be called 'arguments' or 'eval' in strict mode");
  else if (is_strict_reserved_word(name))
- syntax_error("Binding pattern target may not be called 'yield' in strict mode");
+ syntax_error(String::formatted("Binding pattern target may not be called '{}' in strict mode", name));
  }
 }