guard-function-is-non-builtin-ctor.js

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function test() {

  for (var i = 0; i <= 200; ++i) {

    // Create a fresh function in each iteration.

    var values = [function(){}, () => {}];

    // Use an arrow function in the last iteration.

    var useArrowFn = (i === 200);

    // No conditional (?:) so we don't trigger a cold-code bailout.

    var value = values[0 + useArrowFn];

    // Set or create the "prototype" property.

    value.prototype = null;

    // The "prototype" is configurable iff the function is an arrow function.

    var desc = Object.getOwnPropertyDescriptor(value, "prototype");

    assertEq(desc.configurable, useArrowFn);

test();