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import { getOwnPropertyDescriptor } from '../utility';
import { isFunction } from '../base';
// import { isAnyGeneratorFunction } from './index';
// ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- -----
/**
* Detects whether a passed value features an own `prototype` property.
* @param {Function} value
* Assumes a function type but does not check for it.
* @returns {boolean}
* Whether the passed type features an own `prototype` property.
* @category Function Type Detection Helper
*/
export function hasOwnPrototype(value) {
return !!getOwnPropertyDescriptor(value, 'prototype');
}
/**
* Detects whether a passed value features an own, truly `writable`
* `prototype` property.
* @param {Function} value
* Assumes a function type but does not check for it.
* @returns {boolean}
* Whether the passed type features an own, truly `writable`
* `prototype` property.
* @category Function Type Detection Helper
*/
export function hasOwnWritablePrototype(value) {
return getOwnPropertyDescriptor(value, 'prototype')?.writable === true;
}
// ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- ----- -----
/**
* Checks whether a passed `value` is possibly constructable.
*
* It does so by just probing the passed value's `[[construct]]`
* slot; it does never invoke the passed value itself.
*
* The `construct` proxy handler is allowed to overwrite the
* `[[construct]]` slot of a proxied value, but it cannot turn
* something non constructable into a constructable type.
*
* - see ... [https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Proxy/Proxy/construct]
* > "The `handler.construct` method is a trap for the `[[Construct]]`
* > object internal method, which is used by operations such as the
* > `new` operator. In order for the `new` operation to be valid on
* > the resulting `Proxy` object, the `target` used to initialize
* > the proxy must itself be a valid constructor."
* @param {any} value
* @returns {boolean}
* A boolean value which indicates whether the tested
* type could possibly serve as constructor function.
* @category Function Type Detection Helper
*/
export function hasConstructSlot(value) {
let canConstruct = false;
try {
// eslint-disable-next-line no-new
new new Proxy(value, { construct: () => ({}) })();
canConstruct = true;
} catch (err) {
/* empty */
}
return canConstruct;
}
/**
* Detects whether the passed `value` is a constructable function type.
*
* It does so by verifying whether a function has an own `prototype`, and in
* case it does, by additionally just probing the `[[construct]]` slot of the
* passed possibly constructable type; it does never invoke the passed type.
*
* The `construct` proxy handler is allowed to overwrite the
* `[[construct]]` slot of a proxied value, but it cannot turn
* something non constructable into a constructable type.
*
* - see ... [https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Proxy/Proxy/construct]
* > "The `handler.construct` method is a trap for the `[[Construct]]`
* > object internal method, which is used by operations such as the
* > `new` operator. In order for the `new` operation to be valid on
* > the resulting `Proxy` object, the `target` used to initialize
* > the proxy must itself be a valid constructor."
* @param {any} value
* @returns {boolean}
* A boolean value which indicates whether the
* tested type can serve as constructor function.
* @category Function Type Detection Helper
*/
export function isConstructable(value) {
return isFunction(value) && hasOwnPrototype(value) && hasConstructSlot(value);
// return isFunction(value) && hasConstructSlot(value);
}
// /**
// * Detects whether the passed `value` is a constructable
// * function type.
// *
// * It does so by testing the `[[construct]]` slot of the
// * passed possibly constructable type, but it does not
// * invoke it.
// *
// * The `construct` proxy handler is allowed to overwrite
// * the `[[construct]]` slot of a proxied value, but
// * it cannot turn something non constructable into
// * a constructable type.
// *
// * - see ... [https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Proxy/Proxy/construct]
// * > "The `handler.construct` method is a trap for the `[[Construct]]`
// * > object internal method, which is used by operations such as the
// * > `new` operator. In order for the `new` operation to be valid on
// * > the resulting `Proxy` object, the `target` used to initialize
// * > the proxy must itself be a valid constructor."
// *
// * - Thus, it is feasible enough to let the construct trap
// * return an object instance.
// *
// * **Note:**
// *
// * The [[construct]] slot of either generator function type,
// * async or not, indicates that generator functions are not
// * constructable, despite each returning a valid instance of
// * its type when being invoked with just the call/`()` operator.
// *
// * Therefore this implementation of an introspective `isConstructable`
// * functionality recognizes generator functions as _**constructable**_.
// *
// * This method is recommended and **safe**.
// *
// * @param value{any}
// * @returns {boolean}
// * A boolean value which indicates whether the
// * tested type can serve as a constructor function.
// * @category Function Type Detection Helper
// */
// export function isConstructable(value) {
// return (
// isAnyGeneratorFunction(value) || (isFunction(value) && hasConstructSlot(value))
// );
// }
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