net.ParseIP has 1 return value. It doesn't return a value of type error. Other parse methods like url.Parse, time.ParseDuration and net.ParseMAC return 2 values. One of a specific type, the other is of type error.

Please answer these questions before submitting your issue. Thanks!

What version of Go are you using (go version)?

go version go1.7.go version go1.7.4 linux/amd64

What operating system and processor architecture are you using (go env)?

GOARCH="amd64"
GOBIN=""
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="/home/auke/projects/go"
GORACE=""
GOROOT="/usr/lib/go"
GOTOOLDIR="/usr/lib/go/pkg/tool/linux_amd64"
CC="gcc"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build151269634=/tmp/go-build -gno-record-gcc-switches"
CXX="g++"
CGO_ENABLED="1"

What did you do?

If possible, provide a recipe for reproducing the error.
A complete runnable program is good.
A link on play.golang.org is best.

https://play.golang.org/p/d0K77gxoJe

package main

import (
	"fmt"
	"net"
)

func main() {
	// Trying to parse an invalid MAC address results in an error.
	// This is expected behaviour, other Parse methods do also return
	// 2 values, like time.ParseDuration or url.Parse.
	_, err := net.ParseMAC("invalid")

	if er != nil {
		fmt.Println(err)
	}

	// net.ParseIP doesn't follow this signature. It just returns nil
	// when parsing failed.
	ip := net.ParseIP("invalid")
	fmt.Println(ip)
}

What did you expect to see?

I'd expect that net.ParseIP has this signature:

func ParseIP(s string) (IP, error)

What did you see instead?

func ParseIP(s string) IP