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LibJS: Don't treat '?.' followed by decimal digit as QuestionMarkPeriod

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From the spec: https://tc39.es/ecma262/#sec-punctuators

    OptionalChainingPunctuator ::
        ?. [lookahead ∉ DecimalDigit]

We were missing the lookahead and therefore incorrectly treating any
'?.' as TokenType::QuestionMarkPeriod.

Fixes #4409.
This commit is contained in:
Linus Groh 2020-12-14 13:05:24 +00:00 committed by Andreas Kling
parent 6e7edd6e77
commit 0974991d05
Notes: sideshowbarker 2024-07-19 00:52:17 +09:00 
Author: https://github.com/linusg
Commit: https://github.com/SerenityOS/serenity/commit/0974991d051
Pull-request: https://github.com/SerenityOS/serenity/pull/4410
Issue: https://github.com/SerenityOS/serenity/issues/4409
2 changed files with 11 additions and 4 deletions
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11
Libraries/LibJS/Lexer.cpp
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@ -598,10 +598,13 @@ Token Lexer::next()
auto two_chars_view = m_source.substring_view(m_position - 1, 2);
auto it = s_two_char_tokens.find(two_chars_view.hash(), [&](auto& entry) { return entry.key == two_chars_view; });
if (it != s_two_char_tokens.end()) {
found_two_char_token = true;
consume();
consume();
token_type = it->value;
// OptionalChainingPunctuator :: ?. [lookahead ∉ DecimalDigit]
if (!(it->value == TokenType::QuestionMarkPeriod && m_position + 1 < m_source.length() && isdigit(m_source[m_position + 1]))) {
found_two_char_token = true;
consume();
consume();
token_type = it->value;
}
}
}

4
Libraries/LibJS/Tests/operators/ternary-basic.js
View file

@ -14,3 +14,7 @@ test("object values", () => {
expect(o.f ? true : false).toBeTrue();
expect(1 ? o.f : null).toBeTrue();
});
test("issue #4409, '?.' followed by decimal digit", () => {
expect("return false?.1:.2").toEvalTo(0.2);
});