cmd/guru: freevars: reenable test of labels (and improve output)

Change-Id: Icb7747d0856a4be2de52e143b793b52a725d297c
Reviewed-on: https://go-review.googlesource.com/19437
Reviewed-by: Alan Donovan <adonovan@google.com>

cmd/guru/freevars.go

@@ -184,7 +184,7 @@ func (r *freevarsResult) display(printf printfFunc) {
 		for _, ref := range r.refs {
 			// Avoid printing "type T T".
 			var typstr string
-			if ref.kind != "type" {
+			if ref.kind != "type" && ref.kind != "label" {
 				typstr = " " + types.TypeString(ref.typ, qualifier)
 			}
 			printf(ref.obj, "%s %s%s", ref.kind, ref.ref, typstr)

cmd/guru/testdata/src/freevars/main.go

@@ -33,9 +33,8 @@ func main() {
 
 	f(x) // @freevars fv3 "f.x."
 
-	// TODO(adonovan): enable when go/types supports labels.
-loop: // #@freevars fv-def-label "loop:"
+loop: // @freevars fv-def-label "loop:"
 	for {
-		break loop // #@freevars fv-ref-label "break loop"
+		break loop // @freevars fv-ref-label "break loop"
 	}
 }

cmd/guru/testdata/src/freevars/main.golden

@@ -16,3 +16,10 @@ var y rune
 Free identifiers:
 var x int
 
+-------- @freevars fv-def-label --------
+No free identifiers.
+
+-------- @freevars fv-ref-label --------
+Free identifiers:
+label loop
+