Some plugin interactions seem to be broken in ViperServer

[marcoeilers]

The following program verifies with standard Silicon and Carbon, but does not verify in VSCode (with an up to date version of Viper):

adt List[T] {
    Nil()
    Cons(elem: T, next: List[T])
}

adt Pair[S,T] {
    MkPair(fst: S, snd: T)
}

domain ListDomain[T] {
    function length(List[T]): Int

    axiom {
        length((Nil(): List[T])) == 0
    }

    axiom {
        forall l: List[T], e: T :: length(Cons(e, l)) == 1 + length(l)
    }
}

method zip(l1: List[Int], l2: List[Int]) returns (res: List[Pair[Int, Int]])
    decreases l1
    ensures length(l1) == length(l2) ==> length(res) == length(l1)
{

    if(l1 == Nil() || l2 == Nil()) {
        res := Nil()
    } else {
        var rest: List[Pair[Int, Int]] := zip(l1.next, l2.next)
        res := Cons(MkPair(l1.elem, l2.elem), rest)
    }
}

I'm reasonably sure that the problem is that the ADT plugin does not generate the well-foundedness axioms for the List type, and that may be because it does not get a config object that says that the termination plugin is active. So this seems potentially related to #165.

[marcoeilers]

Fixed in #186