cmd/fix: remove redundant 0 port

Fixes #4505.

R=golang-dev, mikioh.mikioh
CC=golang-dev
https://golang.org/cl/7468043

src/cmd/fix/netipv6zone.go

@@ -57,10 +57,15 @@ func netipv6zone(f *ast.File) bool {
 							Value: e,
 						}
 					} else {
-						cl.Elts[i] = &ast.KeyValueExpr{
-							Key:   ast.NewIdent("Port"),
-							Value: e,
+						if e.(*ast.BasicLit).Value == "0" {
+							cl.Elts = append(cl.Elts[:i], cl.Elts[i+1:]...)
+						} else {
+							cl.Elts[i] = &ast.KeyValueExpr{
+								Key:   ast.NewIdent("Port"),
+								Value: e,
+							}
 						}
+
 					}
 				}
 				fixed = true

src/cmd/fix/netipv6zone_test.go

@@ -26,7 +26,8 @@ func f() net.Addr {
 	c := &net.IPAddr{ip1}
 	sub(&net.UDPAddr{ip2, 12345})
 	d := &net.TCPAddr{IP: ip3, Port: 54321}
-	return &net.TCPAddr{ip4}, nil
+	e := &net.TCPAddr{ip4, 0}
+	return &net.TCPAddr{ip5}, nil
 }
 `,
 		Out: `package main
@@ -44,7 +45,8 @@ func f() net.Addr {
 	c := &net.IPAddr{IP: ip1}
 	sub(&net.UDPAddr{IP: ip2, Port: 12345})
 	d := &net.TCPAddr{IP: ip3, Port: 54321}
-	return &net.TCPAddr{IP: ip4}, nil
+	e := &net.TCPAddr{IP: ip4}
+	return &net.TCPAddr{IP: ip5}, nil
 }
 `,
 	},