Problem Matching Sets

[DavePearce]

The following WyRL program:

term X
term Y
term Z
define YZ as Y | Z
term C{X,YZ...}

reduce C{X x,Y,YZ... yzs}:
    => C(x++yzs)

Generates the following probe() code:

public final void probe(Automaton automaton, int target, List activations) {
            int r0 = target;
            Automaton.State s0 = automaton.get(r0);
            if(s0.kind == K_C) {
                Automaton.Term t0 = (Automaton.Term) s0;
                int r1 = t0.contents;
                Automaton.State s1 = automaton.get(r1);
                Automaton.Collection c1 = (Automaton.Collection) s1;
                if(c1.size() >= 2) {
                    for(int r3=0;r3!=c1.size();++r3) {
                        int r2 = c1.get(r3);
                        for(int r5=0;r5!=c1.size();++r5) {
                            if(r5 == r3) { continue; }
                            int r4 = c1.get(r5);
                            if(Runtime.accepts(type1,automaton,automaton.get(r4), SCHEMA)) {
                                int[] state = {r0, r1, r2, r3, r4, r5, 0};
                                activations.add(new Reduction.Activation(this,null,state));
                            }
                        }
                    }
                }
            }
        }

If we look very carefully, we can notice that r2 (which represents x) is never tested against the type X. This generates potentially invalid matches.