Why does testC() fail to compile in the following go code? I would expect that the behavior would match that of testB() with the exception that err's scope would be limited to the if block.
The error message provided by the compiler is resp declared and not used
package main
import "fmt"
func main() {
testA()
testB()
testC()
testD()
}
// valid
func testA() {
resp, err := generateInt()
fmt.Println(fmt.Sprintf("Resp=%v Error=%v", resp, err))
}
// valid
func testB() {
var resp *int
resp, err := generateInt()
fmt.Println(fmt.Sprintf("Resp=%v Error=%v", resp, err))
}
// does not compile
func testC() {
var resp *int
if resp, err := generateInt(); err != nil {
fmt.Println("error=%v", err)
return
}
fmt.Println("Resp=%d", *resp)
}
// valid
func testD() {
var resp *int
var err error
if resp, err = generateInt(); err != nil {
fmt.Println("error=%v", err)
return
}
fmt.Println("Resp=%d", *resp)
}
func generateInt() (*int, error) {
result := 5
return &result, nil
}
In this example:
var resp *int
if resp, err := generateInt(); err != nil {
The short variable declaration is redeclaring the resp variable. Because an if's statement is scoped to the inside the if block, it only shadows the first resp variable within that block, leaving the first unused.
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