Find bugs in JavaScript programs.

E0180: stray comma in function parameter

A function parameter can be a variable name, an array destructuring, or an object destructuring. It is a syntax error for a parameter name to be in parentheses with a comma:

let firsts = data.map([(x,)] => x);

To fix this error, remove the comma:

let firsts = data.map([(x)] => x);

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