from variant to component-type variant?

[Sephirothbahamut]

Greetings,
my current collision system supports multiple shapes (point, segment, circle, aabb, polygon). Each shape has a cast to aabb.
In the current version, there's a "collider" component that is a variant of all the collider types. The collision system (we didn't do any broadphase so far so it's n^2) has a nested foreach with two nested std::visit on the colliders of the pair of entities considered on iteration. Inside the inner visit, it first check for the aabb collision, and if successful for the full collision.

I whish to change the system so that each shape is a different component type, and each entity with collision also has an aabb component. This way I can first make a view for each different shape+aabb, which updates the aabb of all the entities (no variant needed, easily done, no branching, better cache friendliness), then make a view for each aabb with the n^2 loop, (with the same advantages). However if the aabb-aabb collision is true, now I have an issue: how do I know which collider type to get from the two entities to do the final shape-shape check?

I was thinking i could have a variant of pointers to the collider shapes, which would give me all i need, except pointer invalidation creeps in.

Would be nice if I could store an "entt type key", and then have something like std::visit that lets me do registry.visit(entity, type_key, [](auto& component) {...});

The only alternative way to do this I have right now is to make an enum value for each collider type, add the enum as component, and write a massive switch for entity "a" of the collision check, with on each case another massive switch for the entity "b", and each inner case gets the correct shape components from entities a and b, to finally perform the actual check...

[skypjack]

Before answering, let me ask you a question: are the colliders derived from a base class? You could enable pointer stability for the shape types in this case, put a pointer to the base class on the aabb component or any other known component, then rely on the double dispatching to resolve the call. That or any variation of the problem too. For example, an erased function and a void* to the shape component.

[Sephirothbahamut]

They don't have a common parent, but you made me think of an obvious alternative: I have a component that is a variant of pointers to the different shapes. That way I can use std::visit on it.
Thanks!