[eska]

I have to admit I don't quite understand your issue. To me it seems like you've used a lot of OOP and cannot befriend the idea that the data structure (e.g. "Circle" in file GeometryTypes.blub) and operations that are performed with it (e.g. collisions in "CollisionDetection.blub") are completely separate. There should be no discussion whether the circle type and collision belong in the same file, while combinations are in some other file. Think of it like this: if you're going to add 3d rendering of circles, will you put that in Circle.blub together with collision detection? Wouldn't you rather add it to 3DRenderer.blub?

That said, ultimately it doesn't really matter. If you're going to implement collision detection like this, then yes, you will have a combinatorial explosion. This is not a language issue. Switching from Java to some other language with a different form of dispatch will not save you from implementing a lot of algorithms when adding bezier curves into the mix.

The practical approach is reduce the problem to a common case, e.g. to turn the collision shapes into a set of triangles first, and then perform triangle-triangle collision detection.