LibJS: Allow reserved words as keys in object expressions.

Author: https://github.com/sunverwerth
Commit: https://github.com/SerenityOS/serenity/commit/bf5b2516841
Pull-request: https://github.com/SerenityOS/serenity/pull/1849
Issue: https://github.com/SerenityOS/serenity/issues/1768

Libraries/LibJS/Parser.cpp

@@ -437,8 +437,8 @@ NonnullRefPtr<ObjectExpression> Parser::parse_object_expression()
 
     while (!done() && !match(TokenType::CurlyClose)) {
         FlyString property_name;
-        if (match(TokenType::Identifier)) {
-            property_name = consume(TokenType::Identifier).value();
+        if (match_identifier_name()) {
+            property_name = consume().value();
         } else if (match(TokenType::StringLiteral)) {
             property_name = consume(TokenType::StringLiteral).string_value();
         } else if (match(TokenType::NumericLiteral)) {
@@ -582,7 +582,9 @@ NonnullRefPtr<Expression> Parser::parse_secondary_expression(NonnullRefPtr<Expre
         return create_ast_node<AssignmentExpression>(AssignmentOp::Assignment, move(lhs), parse_expression(min_precedence, associativity));
     case TokenType::Period:
         consume();
-        return create_ast_node<MemberExpression>(move(lhs), parse_expression(min_precedence, associativity));
+        if (!match_identifier_name())
+            expected("IdentifierName");
+        return create_ast_node<MemberExpression>(move(lhs), create_ast_node<Identifier>(consume().value()));
     case TokenType::BracketOpen: {
         consume(TokenType::BracketOpen);
         auto expression = create_ast_node<MemberExpression>(move(lhs), parse_expression(0), true);
@@ -1072,6 +1074,11 @@ bool Parser::match_statement() const
         || type == TokenType::Var;
 }
 
+bool Parser::match_identifier_name() const
+{
+    return m_parser_state.m_current_token.is_identifier_name();
+}
+
 bool Parser::done() const
 {
     return match(TokenType::Eof);

Libraries/LibJS/Parser.h

@@ -84,6 +84,7 @@ private:
     bool match_secondary_expression() const;
     bool match_statement() const;
     bool match_variable_declaration() const;
+    bool match_identifier_name() const;
     bool match(TokenType type) const;
     bool done() const;
     void expected(const char* what);

Libraries/LibJS/Tests/object-basic.js

@@ -23,6 +23,14 @@ try {
     // Note : this test doesn't pass yet due to floating-point literals being coerced to i32 on access
     // assert(math[3.14] === "pi");
 
+    // This is also allowed! Watch out for syntax errors.
+    var o2 = { return: 1, yield: 1, for: 1, catch: 1, break: 1 };
+    assert(o2.return === 1);
+    assert(o2.yield === 1);
+    assert(o2.for === 1);
+    assert(o2.catch === 1);
+    assert(o2.break === 1);
+
     console.log("PASS");
 } catch (e) {
     console.log("FAIL: " + e);

Libraries/LibJS/Token.cpp

@@ -129,4 +129,44 @@ bool Token::bool_value() const
     return m_value == "true";
 }
 
+bool Token::is_identifier_name() const
+{
+    // IdentifierNames are Identifiers + ReservedWords
+    // The standard defines this reversed: Identifiers are IdentifierNames except reserved words
+    // https://www.ecma-international.org/ecma-262/5.1/#sec-7.6
+    return m_type == TokenType::Identifier
+        || m_type == TokenType::Await
+        || m_type == TokenType::BoolLiteral
+        || m_type == TokenType::Break
+        || m_type == TokenType::Case
+        || m_type == TokenType::Catch
+        || m_type == TokenType::Class
+        || m_type == TokenType::Const
+        || m_type == TokenType::Continue
+        || m_type == TokenType::Default
+        || m_type == TokenType::Delete
+        || m_type == TokenType::Do
+        || m_type == TokenType::Else
+        || m_type == TokenType::Finally
+        || m_type == TokenType::For
+        || m_type == TokenType::Function
+        || m_type == TokenType::If
+        || m_type == TokenType::In
+        || m_type == TokenType::Instanceof
+        || m_type == TokenType::Interface
+        || m_type == TokenType::Let
+        || m_type == TokenType::New
+        || m_type == TokenType::NullLiteral
+        || m_type == TokenType::Return
+        || m_type == TokenType::Switch
+        || m_type == TokenType::This
+        || m_type == TokenType::Throw
+        || m_type == TokenType::Try
+        || m_type == TokenType::Typeof
+        || m_type == TokenType::Var
+        || m_type == TokenType::Void
+        || m_type == TokenType::While
+        || m_type == TokenType::Yield;
+}
+
 }

Libraries/LibJS/Token.h

@@ -153,6 +153,8 @@ public:
     String string_value() const;
     bool bool_value() const;
 
+    bool is_identifier_name() const;
+
 private:
     TokenType m_type;
     StringView m_trivia;