Questions tagged [covariance]

Covariance, contravariance and invariance describe how the existing type inheritance hierarchy changes when subjected to some transformation (such as usage within generics). If the transformation keeps the ordering of the original hierarchy, it is "covariant". If it reverses it, it is "contravariant". If it breaks it, it is "invariant".

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"fake" covariance in PHP type-hinting

Here's the situation: I've got several distinct objects, each with their own responsability and (therefore) each their own dependencies. As this is code that will be implemented in 2 existing ...
Elias Van Ootegem's user avatar