[b3morales]

I don't think this is the same as "make illegal states unrepresentable"; it's a corollary (or the converse maybe):

"Make assertions of legal states representable"

[joshuamorton]

They're sort of the same. If you have str and safestr, and safestr is known to confiorm to some invariant, the illegal state of a, say str where validate hasn't been called, isn't representable.