Sort error in symbolic execution involving enums (unknown variant)

Symbolic execution can fail (in python client code) with a sort error that `TypedLocal` is not subsort of `TypedValue` when running on functions that take an `enum` as an argument.
The sort error appears to come from side conditions introduced by the legacy backend for branches that we would expect to get pruned (pending further investigation), and involves the `traverseProjection` rewrite symbol.