False positive about unused return values

[cloudlena]

The following code

package main

import "github.com/aws/aws-sdk-go-v2/aws"

func main() {
	_ = aws.EndpointResolverFunc(func(string, string) (aws.Endpoint, error) {
		return aws.Endpoint{URL: "url"}, nil
	})
}

returns the following unparam issue:

main.go:6:67: main$1 - result 1 (error) is always nil

However, I cannot remove that error return value because that would change the function signature and it wouldn't match the one expected by the AWS SDK anymore.

[mvdan]

Thanks. Just to confirm - are you using the latest master version, e6a6d1c? I fixed a few false positives this morning.

[cloudlena]

Yes, I just downloaded it with go get -u mvdan.cc/unparam.

[mvdan]

I can't reproduce it:

$ cat go.mod
module repro

go 1.12

require github.com/aws/aws-sdk-go-v2 v0.7.0
$ cat f.go
package main

import (
        "fmt"

        "github.com/aws/aws-sdk-go-v2/aws"
)

func main() {
        resolver := aws.EndpointResolverFunc(func(string, string) (aws.Endpoint, error) {
                return aws.Endpoint{}, nil
        })
        fmt.Println(resolver)
}
$ unparam .
$

Could you provide the steps to reproduce the problem within a Docker container? That way I'll very likely be able to reproduce it. For example, the following still doesn't show me any unparam warning:

#!/bin/bash

docker run -i golang:1.11.4-stretch <<-SCRIPT

        echo "installing unparam"
        export GO111MODULE=off # to install unparam properly
        go get -u mvdan.cc/unparam

        echo "setting up temp module"
        export GO111MODULE=on
        mkdir temp
        cd temp
        go mod init temp

        cat >f.go <<FILE
        package main

        import (
                "fmt"

                "github.com/aws/aws-sdk-go-v2/aws"
        )

        func main() {
                resolver := aws.EndpointResolverFunc(func(string, string) (aws.Endpoint, error) {
                        return aws.Endpoint{}, nil
                })
                fmt.Println(resolver)
        }
        FILE
        echo "downloading deps"
        go mod tidy

        echo "running unparam"
        unparam .

SCRIPT

[cloudlena]

Sorry, I just noticed that my example was incomplete and, indeed, didn't reproduce the issue. I fixed it above and simplified the example some more and it should work now to reproduce. I had to add URL: "url" for it to reproduce the issue. It works fine without that part.

[mvdan]

Thanks - I can reproduce now. Should be a simple enough fix.