Bug 193057 – Extending a bound function of a non-costructor should throw a TypeError

• Status: RESOLVED
• Resolution: DUPLICATE
• Component: JavaScriptCore

Attempting to extend a bound function whose underlying function is not a constructor (like an arrow function, a generator, etc.) should result in a TypeError as per the specification (https://www.ecma-international.org/ecma-262/9.0/index.html#sec-runtime-semantics-classdefinitionevaluation).

// Test case

const A = (_=>_).bind();
A.prototype = null;
class B extends A {}

// Expected behavior: TypeError should be thrown
// Actual behavior: No error is thrown

[Ross Kirsling]

Looking through our failure list, this doesn't appear to have a test262 test.

Would you be interested in adding one there?
https://github.com/tc39/test262

[Alexey Shvayka]

(In reply to Ross Kirsling from comment #1)
> Looking through our failure list, this doesn't appear to have a test262 test.

JSC doesn't perform IsConstructor during ClassDefinitionEvaluation, failing https://test262.report/browse/language/statements/class/subclass/class-definition-superclass-generator.js. https://webkit.org/b/144093 should fix it.

I am adding a few more tests with bound/proxied arrow/async functions in https://github.com/tc39/test262/pull/2619.

*** This bug has been marked as a duplicate of bug 144093 ***