13b610be03
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Implement three missing JS operators that together unblock 57 Test262 full-suite tests (pass rate 42% → 44%): - delete: reference-aware unary operator that removes object properties, with special handling for member/computed/identifier expressions - void: unary operator that evaluates operand and returns undefined - in: binary operator that checks property existence via prototype chain, gated by allow_in flag to disambiguate from for-in loops The allow_in mechanism (with_no_in helper) prevents the parser from consuming `in` as a binary operator inside for-loop initializers, which would break for-in/for-of parsing. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
23 lines
673 B
JavaScript
23 lines
673 B
JavaScript
// delete on an undeclared identifier returns true (sloppy mode)
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var r1 = delete neverDeclared;
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console.log(r1); // true
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// delete on a declared variable returns false (cannot delete)
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var declared = 42;
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var r2 = delete declared;
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console.log(r2); // false
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// delete on a call expression (non-reference catch-all) returns true
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// and the call expression is still evaluated for side effects
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var sideEffect = 0;
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function bump() { sideEffect = sideEffect + 1; return 1; }
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var r3 = delete bump();
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console.log(r3); // true
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console.log(sideEffect); // 1
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// deleting then reassigning a property works
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var obj = {x: 1};
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delete obj.x;
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obj.x = 99;
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console.log(obj.x); // 99
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