Summary:
Before we were computing the size of an abstract state (`range`) using the `NonNegativeBound` domain but it wasn't able to express product of symbolic values.
This diff introduces a domain for that.
The range of an interval is still computed in `NonNegativeBound` but then the product is done in `TopLiftedPolynomial` so all costs end up being of that type.
The //symbols// of a polynomial are `NonNegativeBound` (so the polynomial only represent non-negative values, perfect for a cost), which handles substitution correctly, i.e. it gives zero instead of negative values.
Reviewed By: ddino
Differential Revision: D7397229
fbshipit-source-id: 6868bb7
Mehdi Bouaziz