Hi,
Occasionally go vet complains about shadowing of the err variable.
Consider the following code.
package main
import (
"flag"
"io"
"os"
)
func main() {
inFilename := flag.String("in", "infile", "input file")
outFilename := flag.String("out", "outfile", "output file")
flag.Parse()
in, err := os.Open(*inFilename)
if err != nil {
panic(err)
}
out, err := os.Create(*outFilename)
if err != nil {
panic(err)
}
buf := make([]byte, 1024)
for {
n, err := in.Read(buf)
if err != nil && err != io.EOF {
panic(err)
}
if n == 0 {
break
}
if _, err := out.Write(buf[:n]); err != nil {
panic(err)
}
}
}
Go vet in strict mode complains:
$ go tool vet -shadow -shadowstrict ./cat.go
./cat.go:26: declaration of "err" shadows declaration at ./cat.go:14
./cat.go:33: declaration of "err" shadows declaration at ./cat.go:26
Is it really a bad practice? What's the alternative?
Declaring all the variables in advance with explicitly specifying their
types, i.e.
var out *os.File
out, err = os.Create(*outFilename)
?
Thanks,
Iakov
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