LibJS: Handle escaped keywords in more cases and handle 'await' labels

Userland/Libraries/LibJS/Parser.cpp

@@ -406,9 +406,7 @@ NonnullRefPtr<Statement> Parser::parse_statement(AllowLabelledFunction allow_lab
  m_state.current_token = m_state.lexer.force_slash_as_regex();
  [[fallthrough]];
  default:
- if (type == TokenType::EscapedKeyword
- && (m_state.strict_mode
- || (m_state.current_token.value() != "yield"sv && m_state.current_token.value() != "let"sv)))
+ if (match_invalid_escaped_keyword())
  syntax_error("Keyword must not contain escaped characters");
 
  if (match_identifier_name()) {
@@ -432,6 +430,20 @@ NonnullRefPtr<Statement> Parser::parse_statement(AllowLabelledFunction allow_lab
  }
 }
 
+bool Parser::match_invalid_escaped_keyword() const
+{
+ if (m_state.current_token.type() != TokenType::EscapedKeyword)
+ return false;
+ auto token_value = m_state.current_token.value();
+ if (token_value == "await"sv) {
+ return m_program_type == Program::Type::Module;
+ }
+ if (m_state.strict_mode) {
+ return true;
+ }
+ return token_value != "yield"sv && token_value != "let"sv;
+}
+
 static constexpr AK::Array<StringView, 9> strict_reserved_words = { "implements", "interface", "let", "package", "private", "protected", "public", "static", "yield" };
 
 static bool is_strict_reserved_word(StringView str)
@@ -582,7 +594,10 @@ RefPtr<Statement> Parser::try_parse_labelled_statement(AllowLabelledFunction all
  };
 
  if (m_state.current_token.value() == "yield"sv && (m_state.strict_mode || m_state.in_generator_function_context)) {
- syntax_error("'yield' label not allowed in this context");
+ return {};
+ }
+
+ if (m_state.current_token.value() == "await"sv && m_program_type == Program::Type::Module) {
  return {};
  }
 
@@ -2854,6 +2869,7 @@ bool Parser::match_expression() const
  || type == TokenType::TemplateLiteralStart
  || type == TokenType::NullLiteral
  || match_identifier()
+ || type == TokenType::Await
  || type == TokenType::New
  || type == TokenType::Class
  || type == TokenType::CurlyOpen
@@ -3026,12 +3042,14 @@ bool Parser::match_identifier() const
  return !m_state.strict_mode;
  if (m_state.current_token.value() == "yield"sv)
  return !m_state.strict_mode && !m_state.in_generator_function_context;
+ if (m_state.current_token.value() == "await"sv)
+ return m_program_type != Program::Type::Module;
  return true;
  }
 
  return m_state.current_token.type() == TokenType::Identifier
  || (m_state.current_token.type() == TokenType::Let && !m_state.strict_mode)
- || (m_state.current_token.type() == TokenType::Await && !m_state.strict_mode)
+ || (m_state.current_token.type() == TokenType::Await && m_program_type != Program::Type::Module)
  || (m_state.current_token.type() == TokenType::Yield && !m_state.in_generator_function_context && !m_state.strict_mode); // See note in Parser::parse_identifier().
 }
 
@@ -3119,10 +3137,10 @@ Token Parser::consume_identifier_reference()
 
  if (match(TokenType::EscapedKeyword)) {
  auto name = m_state.current_token.value();
- if (name == "await"sv)
- syntax_error("Identifier reference may not be 'await'");
- else if (m_state.strict_mode && (name == "let"sv || name == "yield"sv))
+ if (m_state.strict_mode && (name == "let"sv || name == "yield"sv))
  syntax_error(String::formatted("'{}' is not allowed as an identifier in strict mode", name));
+ if (m_program_type == Program::Type::Module && name == "await"sv)
+ syntax_error("'await' is not allowed as an identifier in module");
 
  return consume();
  }
@@ -3141,7 +3159,8 @@ Token Parser::consume_identifier_reference()
  }
 
  if (match(TokenType::Await)) {
- syntax_error("Identifier reference may not be 'await'");
+ if (m_program_type == Program::Type::Module)
+ syntax_error("'await' is not allowed as an identifier in module");
  return consume();
  }
 
@@ -3343,7 +3362,7 @@ NonnullRefPtr<ImportStatement> Parser::parse_import_statement(Program& program)
  expected("import clauses");
  }
 
- auto from_statement = consume(TokenType::Identifier).value();
+ auto from_statement = consume(TokenType::Identifier).original_value();
  if (from_statement != "from"sv)
  syntax_error(String::formatted("Expected 'from' got {}", from_statement));
 

Userland/Libraries/LibJS/Parser.h

@@ -199,6 +199,8 @@ class Parser {
  bool try_parse_arrow_function_expression_failed_at_position(const Position&) const;
  void set_try_parse_arrow_function_expression_failed_at_position(const Position&, bool);
 
+ bool match_invalid_escaped_keyword() const;
+
  struct RulePosition {
  AK_MAKE_NONCOPYABLE(RulePosition);
  AK_MAKE_NONMOVABLE(RulePosition);

Userland/Libraries/LibJS/Tests/labels.js

@@ -110,6 +110,28 @@ test("can use certain 'keywords' as labels", () => {
  expect(`const: { break const; }`).not.toEval();
 });
 
+test("can use certain 'keywords' even in strict mode", () => {
+ "use strict";
+
+ let i = 0;
+ await: {
+ i++;
+ break await;
+ expect().fail();
+ }
+
+ async: {
+ i++;
+ break async;
+ expect().fail();
+ }
+ expect(i).toBe(2);
+
+ expect(`'use strict'; let: { break let; }`).not.toEval();
+
+ expect(`'use strict'; l\u0065t: { break l\u0065t; }`).not.toEval();
+});
+
 test("invalid label usage", () => {
  expect(() =>
  eval(`