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LibJS: Fix syntax error for arrow function non-decl variable assignment

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A regression was introduced in dc9b4da where the parser would
incorrectly parse the assignment of arrow functions to (non-declaration)
variables. For example, consider:

    a = () => {}

Because the parser was aware of default parameters, in
try_parse_arrow_function, the equals sign would be interpreted as a
default argument, leading to incorrect parsing of the overall
expression. Also resulted in some funny behavior
(a = () => {} => {} worked just fine!).

The simple fix is to only look for default parameters if the arrow
function is required to have parenthesis.
This commit is contained in:
Matthew Olsson 2020-05-05 18:05:50 -07:00 • committed by Andreas Kling
parent 3142c4a4fd
commit 419bce6915
Notes: sideshowbarker 2024-07-19 06:56:26 +09:00
2 changed files with 4 additions and 1 deletions
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2
Libraries/LibJS/Parser.cpp
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@ -295,7 +295,7 @@ RefPtr<FunctionExpression> Parser::try_parse_arrow_function_expression(bool expe
} else if (match(TokenType::Identifier)) { } else if (match(TokenType::Identifier)) {
auto parameter_name = consume(TokenType::Identifier).value(); auto parameter_name = consume(TokenType::Identifier).value();
RefPtr<Expression> default_value; RefPtr<Expression> default_value;
if (match(TokenType::Equals)) { if (expect_parens && match(TokenType::Equals)) {
consume(TokenType::Equals); consume(TokenType::Equals);
default_value = parse_expression(0); default_value = parse_expression(0);
} }

3
Libraries/LibJS/Tests/arrow-functions.js
View file

@ -4,6 +4,9 @@ try {
let getNumber = () => 42; let getNumber = () => 42;
assert(getNumber() === 42); assert(getNumber() === 42);
getNumber = () => 99;
assert(getNumber() === 99);
let add = (a, b) => a + b; let add = (a, b) => a + b;
assert(add(2, 3) === 5); assert(add(2, 3) === 5);