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LibJS: Parser refactored to use constexpr precedence table
Replaced implementation dependent on HashMap with a constexpr PrecedenceTable based on array lookup.
This commit is contained in:
Muhammad Zahalqa
Andreas Kling
parent
b36ac88349
commit
5a2ec86048
Notes:
sideshowbarker
2024-07-19 03:21:15 +09:00
Author: https://github.com/tryfinally Commit: https://github.com/SerenityOS/serenity/commit/5a2ec860487 Pull-request: https://github.com/SerenityOS/serenity/pull/3207
3 changed files with 116 additions and 102 deletions
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@ -26,7 +26,6 @@
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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/ScopeGuard.h>
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#include <AK/StdLibExtras.h>
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@ -66,7 +65,117 @@ public:
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unsigned m_mask { 0 };
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};
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static HashMap<TokenType, int> g_operator_precedence;
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class OperatorPrecedenceTable {
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public:
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constexpr OperatorPrecedenceTable()
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: m_token_precedence()
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{
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for (size_t i = 0; i < array_size(m_operator_precedence); ++i) {
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auto& op = m_operator_precedence[i];
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m_token_precedence[static_cast<size_t>(op.token)] = op.precedence;
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}
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}
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constexpr int get(TokenType token) const
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{
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int p = m_token_precedence[static_cast<size_t>(token)];
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if (p == 0) {
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fprintf(stderr, "Internal Error: No precedence for operator %s\n", Token::name(token));
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ASSERT_NOT_REACHED();
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return -1;
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}
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return p;
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}
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private:
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int m_token_precedence[cs_num_of_js_tokens];
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struct OperatorPrecedence {
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TokenType token;
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int precedence;
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};
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// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Operator_Precedence
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static constexpr const OperatorPrecedence m_operator_precedence[] = {
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{ TokenType::Period, 20 },
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{ TokenType::BracketOpen, 20 },
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{ TokenType::ParenOpen, 20 },
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{ TokenType::QuestionMarkPeriod, 20 },
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{ TokenType::New, 19 },
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{ TokenType::PlusPlus, 18 },
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{ TokenType::MinusMinus, 18 },
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{ TokenType::ExclamationMark, 17 },
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{ TokenType::Tilde, 17 },
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{ TokenType::Typeof, 17 },
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{ TokenType::Void, 17 },
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{ TokenType::Delete, 17 },
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{ TokenType::Await, 17 },
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{ TokenType::DoubleAsterisk, 16 },
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{ TokenType::Asterisk, 15 },
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{ TokenType::Slash, 15 },
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{ TokenType::Percent, 15 },
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{ TokenType::Plus, 14 },
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{ TokenType::Minus, 14 },
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{ TokenType::ShiftLeft, 13 },
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{ TokenType::ShiftRight, 13 },
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{ TokenType::UnsignedShiftRight, 13 },
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{ TokenType::LessThan, 12 },
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{ TokenType::LessThanEquals, 12 },
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{ TokenType::GreaterThan, 12 },
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{ TokenType::GreaterThanEquals, 12 },
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{ TokenType::In, 12 },
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{ TokenType::Instanceof, 12 },
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{ TokenType::EqualsEquals, 11 },
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{ TokenType::ExclamationMarkEquals, 11 },
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{ TokenType::EqualsEqualsEquals, 11 },
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{ TokenType::ExclamationMarkEqualsEquals, 11 },
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{ TokenType::Ampersand, 10 },
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{ TokenType::Caret, 9 },
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{ TokenType::Pipe, 8 },
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{ TokenType::DoubleQuestionMark, 7 },
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{ TokenType::DoubleAmpersand, 6 },
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{ TokenType::DoublePipe, 5 },
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{ TokenType::QuestionMark, 4 },
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{ TokenType::Equals, 3 },
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{ TokenType::PlusEquals, 3 },
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{ TokenType::MinusEquals, 3 },
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{ TokenType::DoubleAsteriskEquals, 3 },
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{ TokenType::AsteriskEquals, 3 },
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{ TokenType::SlashEquals, 3 },
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{ TokenType::PercentEquals, 3 },
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{ TokenType::ShiftLeftEquals, 3 },
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{ TokenType::ShiftRightEquals, 3 },
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{ TokenType::UnsignedShiftRightEquals, 3 },
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{ TokenType::AmpersandEquals, 3 },
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{ TokenType::PipeEquals, 3 },
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{ TokenType::CaretEquals, 3 },
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{ TokenType::Yield, 2 },
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{ TokenType::Comma, 1 },
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};
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};
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constexpr OperatorPrecedenceTable g_operator_precedence;
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Parser::ParserState::ParserState(Lexer lexer)
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: m_lexer(move(lexer))
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, m_current_token(m_lexer.next())
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@ -76,94 +185,6 @@ Parser::ParserState::ParserState(Lexer lexer)
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Parser::Parser(Lexer lexer)
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: m_parser_state(move(lexer))
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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::DoubleAsteriskEquals, 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::AmpersandEquals, 3);
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g_operator_precedence.set(TokenType::PipeEquals, 3);
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g_operator_precedence.set(TokenType::CaretEquals, 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, "Internal Error: 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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@ -627,7 +648,7 @@ NonnullRefPtr<RegExpLiteral> Parser::parse_regexp_literal()
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NonnullRefPtr<Expression> Parser::parse_unary_prefixed_expression()
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{
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auto precedence = operator_precedence(m_parser_state.m_current_token.type());
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auto precedence = g_operator_precedence.get(m_parser_state.m_current_token.type());
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auto associativity = operator_associativity(m_parser_state.m_current_token.type());
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switch (m_parser_state.m_current_token.type()) {
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case TokenType::PlusPlus: {
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@ -918,7 +939,7 @@ NonnullRefPtr<Expression> Parser::parse_expression(int min_precedence, Associati
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expression = create_ast_node<TaggedTemplateLiteral>(move(expression), move(template_literal));
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}
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while (match_secondary_expression(forbidden)) {
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int new_precedence = operator_precedence(m_parser_state.m_current_token.type());
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int new_precedence = g_operator_precedence.get(m_parser_state.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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@ -1135,7 +1156,7 @@ NonnullRefPtr<NewExpression> Parser::parse_new_expression()
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{
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consume(TokenType::New);
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auto callee = parse_expression(g_operator_precedence.get(TokenType::New).value(), Associativity::Right, { TokenType::ParenOpen });
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auto callee = parse_expression(g_operator_precedence.get(TokenType::New), Associativity::Right, { TokenType::ParenOpen });
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Vector<CallExpression::Argument> arguments;
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@ -121,7 +121,6 @@ public:
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private:
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friend class ScopePusher;
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int operator_precedence(TokenType) const;
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Associativity operator_associativity(TokenType) const;
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bool match_expression() const;
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bool match_unary_prefixed_expression() const;
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@ -153,7 +153,9 @@ enum class TokenType {
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#define __ENUMERATE_JS_TOKEN(x) x,
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ENUMERATE_JS_TOKENS
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#undef __ENUMERATE_JS_TOKEN
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_COUNT_OF_TOKENS
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};
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constexpr size_t cs_num_of_js_tokens = static_cast<size_t>(TokenType::_COUNT_OF_TOKENS);
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class Token {
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public:
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@ -196,11 +198,3 @@ private:
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};
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}
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namespace AK {
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template<>
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struct Traits<JS::TokenType> : public GenericTraits<JS::TokenType> {
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static constexpr bool is_trivial() { return true; }
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static unsigned hash(JS::TokenType t) { return int_hash((int)t); }
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};
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}
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