* MinimalCollection, which throws NullPointerException on calls to
     * contains(null).
     */
    List<E> disjointList = Arrays.asList(e3(), e4());
    disjoint = new Target(disjointList, "disjoint");
    superset = new Target(MinimalCollection.of(e0(), e1(), e2(), e3(), e4()), "superset");
    nonEmptyProperSubset = new Target(MinimalCollection.of(e1()), "subset");

		{"/a/{z}/a/{m...}", "/{x}/b", disjoint},

		// Dollar on left.
		{"/{$}", "/a", disjoint},
		{"/{$}", "/a/b", disjoint},
		{"/{$}", "/{$}", equivalent},
		{"/{$}", "/{x}", disjoint},
		{"/{$}", "/", moreSpecific},
		{"/{$}", "/{x...}", moreSpecific},

		{"/b/{$}", "/b", disjoint},
		{"/b/{$}", "/b/a", disjoint},
		{"/b/{$}", "/b/a/b", disjoint},
		{"/b/{$}", "/b/{$}", equivalent},

	}
	// ∅ ⊂ x, y ⊂ 𝓤

	if x.disjoint(y) {
		return false // x ⊆ y == false if x ∩ y == ∅
	}
	// x.typ == y.typ

	// ~t ⊆ ~t == true
	// ~t ⊆ T == false
	//  T ⊆ ~t == true
	//  T ⊆  T == true
	return !x.tilde || y.tilde
}

// disjoint reports whether x ∩ y == ∅.
// x.typ and y.typ must not be nil.
func (x *term) disjoint(y *term) bool {
	if debug && (x.typ == nil || y.typ == nil) {

	}
	// ∅ ⊂ x, y ⊂ 𝓤

	if x.disjoint(y) {
		return false // x ⊆ y == false if x ∩ y == ∅
	}
	// x.typ == y.typ

	// ~t ⊆ ~t == true
	// ~t ⊆ T == false
	//  T ⊆ ~t == true
	//  T ⊆  T == true
	return !x.tilde || y.tilde
}

// disjoint reports whether x ∩ y == ∅.
// x.typ and y.typ must not be nil.
func (x *term) disjoint(y *term) bool {
	if debug && (x.typ == nil || y.typ == nil) {

	}
	// ∅ ⊂ x, y ⊂ 𝓤

	if x.disjoint(y) {
		return false // x ⊆ y == false if x ∩ y == ∅
	}
	// x.typ == y.typ

	// ~t ⊆ ~t == true
	// ~t ⊆ T == false
	//  T ⊆ ~t == true
	//  T ⊆  T == true
	return !x.tilde || y.tilde
}

// disjoint reports whether x ∩ y == ∅.
// x.typ and y.typ must not be nil.
func (x *term) disjoint(y *term) bool {
	if debug && (x.typ == nil || y.typ == nil) {

		args := split(test, 3)
		x := testTerm(args[0])
		y := testTerm(args[1])
		want := args[2] == "T"
		if got := x.disjoint(y); got != want {
			t.Errorf("%v.disjoint(%v) = %v; want %v", x, y, got, want)
		}
		// disjoint is symmetric
		x, y = y, x
		if got := x.disjoint(y); got != want {
			t.Errorf("%v.disjoint(%v) = %v; want %v", x, y, got, want)
		}
	}

		args := split(test, 3)
		x := testTerm(args[0])
		y := testTerm(args[1])
		want := args[2] == "T"
		if got := x.disjoint(y); got != want {
			t.Errorf("%v.disjoint(%v) = %v; want %v", x, y, got, want)
		}
		// disjoint is symmetric
		x, y = y, x
		if got := x.disjoint(y); got != want {
			t.Errorf("%v.disjoint(%v) = %v; want %v", x, y, got, want)
		}
	}

     * MinimalCollection, which throws NullPointerException on calls to
     * contains(null).
     */
    List<E> disjointList = Arrays.asList(e3(), e4());
    disjoint = new Target(disjointList, "disjoint");
    superset = new Target(MinimalCollection.of(e0(), e1(), e2(), e3(), e4()), "superset");
    nonEmptyProperSubset = new Target(MinimalCollection.of(e1()), "subset");

// they overlap.
func combineRelationships(r1, r2 relationship) relationship {
	switch r1 {
	case equivalent:
		return r2
	case disjoint:
		return disjoint
	case overlaps:
		if r2 == disjoint {
			return disjoint
		}
		return overlaps
	case moreGeneral, moreSpecific:
		switch r2 {
		case equivalent:
			return r1
		case inverseRelationship(r1):
			return overlaps

// overlapping (not disjoint) from y. The result is < 0 if there is no
// such term. The type of term y must not be an interface, and terms
// with an interface type are ignored in the terms list.
func overlappingTerm(terms []*Term, y *Term) int {
	assert(!IsInterface(y.typ))
	for i, x := range terms {
		if IsInterface(x.typ) {
			continue
		}
		// disjoint requires non-nil, non-top arguments,