Problem with templates and code reuse

[Frago9876543210]

I have abstract class BaseElementWithValue<TValue> and I want to make an array of elements that inherit BaseElementWithValue<TValue>. The TValue generic allows to avoid duplicating code.

So there can be multiple UI elements:

class Toggle extends BaseElementWithValue<TValue = bool> { ... }
class Input extends BaseElementWithValue<TValue = string> { ... }

(new Toggle(...))->getValue(); /*returns bool*/
(new Input(...))->getValue()); /*returns string*/

Then I want to pass an array of these elements to parameters with type list<BaseElementWithValue<mixed>>. However this doesn't work at level 9 and requires template-covariant.

Example: https://phpstan.org/r/ee15750b-730c-4f7d-aa95-f13f46695685
More complex code is available here: https://github.com/Frago9876543210/forms/blob/master/src/forms/element/Toggle.php#L12

[ondrejmirtes]

What's your question?

One possible solution to the error is:https://phpstan.org/r/c364dacb-1f1f-448e-9177-5b0e9e0d4279

See: https://phpstan.org/blog/guide-to-call-site-generic-variance