proposal: support "var identifier = _" to mute an identifier in certain scope.

[zigo101]

This is helpful to avoid using some identifiers which should be used in some scopes carelessly.

Example:

package main

func main(){
    var n = 123,
    // use n

    {
        // use n

        var n = _
        // now n disppears
    }

    // here, n is still alive
    // use n
}

[stemar94]

you can simply shadow your variables

var n = 123
{
    // use n

    n := n // or var n = n
    // now the real n can no longer be accessed
}
// here, n is still alive

https://play.golang.org/p/KOUBa5TVIv

[zigo101]

you can simply shadow your variables

it is not totally the same

[stemar94]

How about

const n = 1i // complex number

or

n_ := n
\\ no longer allowed to use/change n
if n != n_ {
    panic("n was modified")
}

I still don't get your use case.

[stemar94]

Maybe you want to solve it like this:
https://play.golang.org/p/r1cG8oPS8I

[cznic]

Put this into any of your *_test.go files

func use(...interface{}) {}

Silent the unused variable(s) error anywhere by writing

use(n, o, p)

Bonus: The program does not build when not testing.

[zigo101]

a more detailed example:

package main

func main(){
    var n = 123
    n++ // use n

    {
        n++ // use n

        var n = _ // this one will change spec few
        // now n disppears

        n++ // compiling error: n is undefined
    }

    // here, n is still alive
    n++ 

    var n = _ // // this one will change spec much
    // now n disppears

    n++ // compiling error: n is undefined

}

It is like the "unset" in some languages.

[mattn]

use unnamed vars

var n int
_ = n

var n int; _ = n

[stemar94]

I already got what you want to accomplish, but I don't get what it is good for.

[zigo101]

I already got what you want to accomplish, but I don't get what it is good for.

just let compiler report errors, just like the two error lines in my example. :)

[zigo101]

@mattn,

use unnamed vars

This is not my intention.

[zigo101]

@cznic, I don't get your code.

[stemar94]

@cznic, I don't get your code.

It's also only for using unused vars, so not what you want.

[bradfitz]

Sorry, previous discussions of overloading _ to mean new things (such as the zero value when _ is used on the RHS) have been rejected. This is similarly not an acceptable language change.