I believe vet shadow is known to have issues and is quite picky ;-)
Your first one I'd say could be classed as bug as you're clearly
declaring n however I'd guess this is due to the for loop as declaring n
out of the loop eliminating the short declaration will fix it. This is
confirmed by eliminating the for which also eliminates the warning.
Your second warning (|cat.go:33) |I'd say is correct as you don't
declare a new variable hence err is declared unnecessarily. I'm not sure
if go will actually redeclare a new var under the hood, but as err is
already available just reuse it.
On 23/11/2016 10:46, iakov.davy...@gmail.com wrote:
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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