Clearly these should do different things. I suppose "computeArea(shape)" does dynamic dispatch based on the type of shape? But you're still putting every function defined on every type in your entire codebase in a global namespace. It's not obviously awful but I'd definitely be a bit nervous about it.
You only need dynamic dispatch if dynamic types are involved. If you can always resolve to concrete types, then you can statically resolve the required function.
Square.computeArea()
Circle.computeArea()
Clearly these should do different things. I suppose "computeArea(shape)" does dynamic dispatch based on the type of shape? But you're still putting every function defined on every type in your entire codebase in a global namespace. It's not obviously awful but I'd definitely be a bit nervous about it.