Lets allow collections to be indexed by any \Stringable values

[lkankowski]

Collection could be indexed with any \Stringable value (currently only string|int), for example Ramsey\Uuid.
For Doctrine Collections package it aplys to get, set, remove, containsKey methods.

In Doctrine ORM it is related to bellow relation, but it will probably work just with change signature of above methods.

<one-to-many field="someCollection"
                         target-entity="SomeEntity"
                         mapped-by="parent"
                         index-by="uuidField" />

[stof]

Methods actually returning keys won't be able to return Stringable keys, because this would require being able to store them without casting them. PHP does not have a map type allowing arbitrary values as keys.