get rid of report.Topologies()

The three report.Walk* functions are quite enough.

report/report.go

@@ -273,16 +273,6 @@ func (r Report) Merge(other Report) Report {
 	return newReport
 }
 
-// Topologies returns a slice of Topologies in this report
-func (r Report) Topologies() []Topology {
-	result := make([]Topology, len(topologyNames))
-	for i, name := range topologyNames {
-		t, _ := r.Topology(name)
-		result[i] = t
-	}
-	return result
-}
-
 // WalkTopologies iterates through the Topologies of the report,
 // potentially modifying them
 func (r *Report) WalkTopologies(f func(*Topology)) {
@@ -358,8 +348,8 @@ func (r Report) Topology(name string) (Topology, bool) {
 // Validate checks the report for various inconsistencies.
 func (r Report) Validate() error {
 	var errs []string
-	for _, topology := range r.Topologies() {
-		if err := topology.Validate(); err != nil {
+	for _, name := range topologyNames {
+		if err := r.topology(name).Validate(); err != nil {
 			errs = append(errs, err.Error())
 		}
 	}

report/report_test.go

@@ -20,14 +20,18 @@ func TestReportTopologies(t *testing.T) {
 		topologyType = reflect.TypeOf(report.MakeTopology())
 	)
 
-	var want int
+	var want, have int
 	for i := 0; i < reportType.NumField(); i++ {
 		if reportType.Field(i).Type == topologyType {
 			want++
 		}
 	}
 
-	if have := len(report.MakeReport().Topologies()); want != have {
+	r := report.MakeReport()
+	r.WalkTopologies(func(_ *report.Topology) {
+		have++
+	})
+	if want != have {
 		t.Errorf("want %d, have %d", want, have)
 	}
 }