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https://github.com/RGBCube/serenity
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LibJS: Add operator precedence parsing
Obey precedence and associativity rules when parsing expressions with chained operators.
This commit is contained in:
Stephan Unverwerth
Andreas Kling
parent
f347dd5c5e
commit
15d5b2d29e
8 changed files with 281 additions and 53 deletions
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@ -25,14 +25,142 @@
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*/
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#include "Parser.h"
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#include <AK/HashMap.h>
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#include <AK/StdLibExtras.h>
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#include <stdio.h>
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namespace JS {
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static HashMap<TokenType, int> g_operator_precedence;
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Parser::Parser(Lexer lexer)
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: m_lexer(move(lexer))
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, m_current_token(m_lexer.next())
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{
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if (g_operator_precedence.is_empty()) {
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// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Operator_Precedence
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g_operator_precedence.set(TokenType::Period, 20);
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g_operator_precedence.set(TokenType::BracketOpen, 20);
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g_operator_precedence.set(TokenType::ParenOpen, 20);
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g_operator_precedence.set(TokenType::QuestionMarkPeriod, 20);
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g_operator_precedence.set(TokenType::New, 19);
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g_operator_precedence.set(TokenType::PlusPlus, 18);
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g_operator_precedence.set(TokenType::MinusMinus, 18);
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g_operator_precedence.set(TokenType::ExclamationMark, 17);
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g_operator_precedence.set(TokenType::Tilde, 17);
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g_operator_precedence.set(TokenType::Typeof, 17);
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g_operator_precedence.set(TokenType::Void, 17);
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g_operator_precedence.set(TokenType::Delete, 17);
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g_operator_precedence.set(TokenType::Await, 17);
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g_operator_precedence.set(TokenType::DoubleAsterisk, 16);
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g_operator_precedence.set(TokenType::Asterisk, 15);
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g_operator_precedence.set(TokenType::Slash, 15);
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g_operator_precedence.set(TokenType::Percent, 15);
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g_operator_precedence.set(TokenType::Plus, 14);
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g_operator_precedence.set(TokenType::Minus, 14);
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g_operator_precedence.set(TokenType::ShiftLeft, 13);
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g_operator_precedence.set(TokenType::ShiftRight, 13);
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g_operator_precedence.set(TokenType::UnsignedShiftRight, 13);
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g_operator_precedence.set(TokenType::LessThan, 12);
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g_operator_precedence.set(TokenType::LessThanEquals, 12);
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g_operator_precedence.set(TokenType::GreaterThan, 12);
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g_operator_precedence.set(TokenType::GreaterThanEquals, 12);
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g_operator_precedence.set(TokenType::In, 12);
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g_operator_precedence.set(TokenType::Instanceof, 12);
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g_operator_precedence.set(TokenType::EqualsEquals, 11);
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g_operator_precedence.set(TokenType::ExclamationMarkEquals, 11);
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g_operator_precedence.set(TokenType::EqualsEqualsEquals, 11);
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g_operator_precedence.set(TokenType::ExclamationMarkEqualsEquals, 11);
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g_operator_precedence.set(TokenType::Ampersand, 10);
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g_operator_precedence.set(TokenType::Caret, 9);
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g_operator_precedence.set(TokenType::Pipe, 8);
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g_operator_precedence.set(TokenType::DoubleQuestionMark, 7);
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g_operator_precedence.set(TokenType::DoubleAmpersand, 6);
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g_operator_precedence.set(TokenType::DoublePipe, 5);
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g_operator_precedence.set(TokenType::QuestionMark, 4);
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g_operator_precedence.set(TokenType::Equals, 3);
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g_operator_precedence.set(TokenType::PlusEquals, 3);
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g_operator_precedence.set(TokenType::MinusEquals, 3);
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g_operator_precedence.set(TokenType::AsteriskAsteriskEquals, 3);
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g_operator_precedence.set(TokenType::AsteriskEquals, 3);
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g_operator_precedence.set(TokenType::SlashEquals, 3);
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g_operator_precedence.set(TokenType::PercentEquals, 3);
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g_operator_precedence.set(TokenType::ShiftLeftEquals, 3);
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g_operator_precedence.set(TokenType::ShiftRightEquals, 3);
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g_operator_precedence.set(TokenType::UnsignedShiftRightEquals, 3);
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g_operator_precedence.set(TokenType::PipeEquals, 3);
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g_operator_precedence.set(TokenType::Yield, 2);
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g_operator_precedence.set(TokenType::Comma, 1);
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}
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}
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int Parser::operator_precedence(TokenType type) const
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{
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auto it = g_operator_precedence.find(type);
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if (it == g_operator_precedence.end()) {
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fprintf(stderr, "No precedence for operator %s\n", Token::name(type));
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ASSERT_NOT_REACHED();
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return -1;
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}
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return it->value;
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}
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Associativity Parser::operator_associativity(TokenType type) const
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{
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switch (type) {
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case TokenType::Period:
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case TokenType::BracketOpen:
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case TokenType::ParenOpen:
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case TokenType::QuestionMarkPeriod:
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case TokenType::Asterisk:
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case TokenType::Slash:
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case TokenType::Percent:
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case TokenType::Plus:
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case TokenType::Minus:
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case TokenType::ShiftLeft:
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case TokenType::ShiftRight:
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case TokenType::UnsignedShiftRight:
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case TokenType::LessThan:
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case TokenType::LessThanEquals:
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case TokenType::GreaterThan:
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case TokenType::GreaterThanEquals:
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case TokenType::In:
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case TokenType::Instanceof:
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case TokenType::EqualsEquals:
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case TokenType::ExclamationMarkEquals:
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case TokenType::EqualsEqualsEquals:
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case TokenType::ExclamationMarkEqualsEquals:
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case TokenType::Ampersand:
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case TokenType::Caret:
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case TokenType::Pipe:
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case TokenType::DoubleQuestionMark:
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case TokenType::DoubleAmpersand:
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case TokenType::DoublePipe:
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case TokenType::Comma:
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return Associativity::Left;
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default:
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return Associativity::Right;
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}
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}
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NonnullOwnPtr<Program> Parser::parse_program()
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@ -54,7 +182,7 @@ NonnullOwnPtr<Program> Parser::parse_program()
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NonnullOwnPtr<Statement> Parser::parse_statement()
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{
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if (match_expression()) {
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return make<JS::ExpressionStatement>(parse_expression());
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return make<JS::ExpressionStatement>(parse_expression(0));
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}
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switch (m_current_token.type()) {
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@ -83,7 +211,7 @@ NonnullOwnPtr<Expression> Parser::parse_primary_expression()
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switch (m_current_token.type()) {
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case TokenType::ParenOpen: {
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consume(TokenType::ParenOpen);
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auto expression = parse_expression();
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auto expression = parse_expression(0);
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consume(TokenType::ParenClose);
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return expression;
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}
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@ -113,68 +241,75 @@ NonnullOwnPtr<ObjectExpression> Parser::parse_object_expression()
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return make<ObjectExpression>();
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}
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NonnullOwnPtr<Expression> Parser::parse_expression()
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NonnullOwnPtr<Expression> Parser::parse_expression(int min_precedence, Associativity associativity)
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{
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auto expression = parse_primary_expression();
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while (match_secondary_expression()) {
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expression = parse_secondary_expression(move(expression));
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int new_precedence = operator_precedence(m_current_token.type());
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if (new_precedence < min_precedence)
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break;
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if (new_precedence == min_precedence && associativity == Associativity::Left)
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break;
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Associativity new_associativity = operator_associativity(m_current_token.type());
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expression = parse_secondary_expression(move(expression), new_precedence, new_associativity);
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}
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return expression;
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}
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NonnullOwnPtr<Expression> Parser::parse_secondary_expression(NonnullOwnPtr<Expression> lhs)
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NonnullOwnPtr<Expression> Parser::parse_secondary_expression(NonnullOwnPtr<Expression> lhs, int min_precedence, Associativity associativity)
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{
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switch (m_current_token.type()) {
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case TokenType::Plus:
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consume();
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return make<BinaryExpression>(BinaryOp::Plus, move(lhs), parse_expression());
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return make<BinaryExpression>(BinaryOp::Plus, move(lhs), parse_expression(min_precedence, associativity));
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case TokenType::PlusEquals:
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consume();
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return make<AssignmentExpression>(AssignmentOp::AdditionAssignment, move(lhs), parse_expression());
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return make<AssignmentExpression>(AssignmentOp::AdditionAssignment, move(lhs), parse_expression(min_precedence, associativity));
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case TokenType::Minus:
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consume();
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return make<BinaryExpression>(BinaryOp::Minus, move(lhs), parse_expression());
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return make<BinaryExpression>(BinaryOp::Minus, move(lhs), parse_expression(min_precedence, associativity));
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case TokenType::MinusEquals:
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consume();
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return make<AssignmentExpression>(AssignmentOp::SubtractionAssignment, move(lhs), parse_expression());
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return make<AssignmentExpression>(AssignmentOp::SubtractionAssignment, move(lhs), parse_expression(min_precedence, associativity));
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case TokenType::Asterisk:
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consume();
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return make<BinaryExpression>(BinaryOp::Asterisk, move(lhs), parse_expression());
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return make<BinaryExpression>(BinaryOp::Asterisk, move(lhs), parse_expression(min_precedence, associativity));
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case TokenType::AsteriskEquals:
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consume();
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return make<AssignmentExpression>(AssignmentOp::MultiplicationAssignment, move(lhs), parse_expression());
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return make<AssignmentExpression>(AssignmentOp::MultiplicationAssignment, move(lhs), parse_expression(min_precedence, associativity));
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case TokenType::Slash:
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consume();
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return make<BinaryExpression>(BinaryOp::Slash, move(lhs), parse_expression());
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return make<BinaryExpression>(BinaryOp::Slash, move(lhs), parse_expression(min_precedence, associativity));
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case TokenType::SlashEquals:
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consume();
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return make<AssignmentExpression>(AssignmentOp::DivisionAssignment, move(lhs), parse_expression());
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return make<AssignmentExpression>(AssignmentOp::DivisionAssignment, move(lhs), parse_expression(min_precedence, associativity));
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case TokenType::GreaterThan:
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consume();
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return make<BinaryExpression>(BinaryOp::GreaterThan, move(lhs), parse_expression());
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return make<BinaryExpression>(BinaryOp::GreaterThan, move(lhs), parse_expression(min_precedence, associativity));
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case TokenType::GreaterThanEquals:
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consume();
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return make<BinaryExpression>(BinaryOp::GreaterThanEquals, move(lhs), parse_expression());
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return make<BinaryExpression>(BinaryOp::GreaterThanEquals, move(lhs), parse_expression(min_precedence, associativity));
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case TokenType::LessThan:
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consume();
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return make<BinaryExpression>(BinaryOp::LessThan, move(lhs), parse_expression());
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return make<BinaryExpression>(BinaryOp::LessThan, move(lhs), parse_expression(min_precedence, associativity));
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case TokenType::LessThanEquals:
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consume();
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return make<BinaryExpression>(BinaryOp::LessThanEquals, move(lhs), parse_expression());
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return make<BinaryExpression>(BinaryOp::LessThanEquals, move(lhs), parse_expression(min_precedence, associativity));
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case TokenType::EqualsEqualsEquals:
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consume();
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return make<BinaryExpression>(BinaryOp::TypedEquals, move(lhs), parse_expression());
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return make<BinaryExpression>(BinaryOp::TypedEquals, move(lhs), parse_expression(min_precedence, associativity));
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case TokenType::ExclamationMarkEqualsEquals:
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consume();
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return make<BinaryExpression>(BinaryOp::TypedInequals, move(lhs), parse_expression());
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return make<BinaryExpression>(BinaryOp::TypedInequals, move(lhs), parse_expression(min_precedence, associativity));
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case TokenType::ParenOpen:
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return parse_call_expression(move(lhs));
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case TokenType::Equals:
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consume();
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return make<AssignmentExpression>(AssignmentOp::Assignment, move(lhs), parse_expression());
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return make<AssignmentExpression>(AssignmentOp::Assignment, move(lhs), parse_expression(min_precedence, associativity));
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case TokenType::Period:
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consume();
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return make<MemberExpression>(move(lhs), parse_expression());
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return make<MemberExpression>(move(lhs), parse_expression(min_precedence, associativity));
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case TokenType::PlusPlus:
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consume();
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return make<UpdateExpression>(UpdateOp::Increment, move(lhs));
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@ -196,7 +331,7 @@ NonnullOwnPtr<CallExpression> Parser::parse_call_expression(NonnullOwnPtr<Expres
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NonnullOwnPtrVector<Expression> arguments;
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while (match_expression()) {
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arguments.append(parse_expression());
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arguments.append(parse_expression(0));
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if (!match(TokenType::Comma))
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break;
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consume();
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@ -204,20 +339,14 @@ NonnullOwnPtr<CallExpression> Parser::parse_call_expression(NonnullOwnPtr<Expres
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consume(TokenType::ParenClose);
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// FIXME: Allow lhs expression instead of just a string
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if (lhs->is_identifier()) {
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return make<CallExpression>(static_cast<Identifier*>(lhs.ptr())->string(), move(arguments));
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}
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m_has_errors = true;
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return make<CallExpression>("***ERROR***");
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return make<CallExpression>(move(lhs), move(arguments));
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}
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NonnullOwnPtr<ReturnStatement> Parser::parse_return_statement()
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{
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consume(TokenType::Return);
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if (match_expression()) {
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return make<ReturnStatement>(parse_expression());
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return make<ReturnStatement>(parse_expression(0));
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}
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return make<ReturnStatement>(nullptr);
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}
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@ -283,7 +412,7 @@ NonnullOwnPtr<VariableDeclaration> Parser::parse_variable_declaration()
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OwnPtr<Expression> initializer;
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if (match(TokenType::Equals)) {
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consume();
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initializer = parse_expression();
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initializer = parse_expression(0);
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}
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return make<VariableDeclaration>(make<Identifier>(name), move(initializer), declaration_type);
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}
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@ -313,7 +442,7 @@ NonnullOwnPtr<ForStatement> Parser::parse_for_statement()
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case TokenType::Semicolon:
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break;
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default:
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test = parse_expression();
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test = parse_expression(0);
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break;
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}
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@ -324,7 +453,7 @@ NonnullOwnPtr<ForStatement> Parser::parse_for_statement()
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case TokenType::Semicolon:
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break;
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default:
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update = parse_expression();
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update = parse_expression(0);
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break;
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}
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@ -405,9 +534,9 @@ bool Parser::done() const
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Token Parser::consume()
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{
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auto oldToken = m_current_token;
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auto old_token = m_current_token;
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m_current_token = m_lexer.next();
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return oldToken;
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return old_token;
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}
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Token Parser::consume(TokenType type)
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