"Ineffectual assignment" false positive when var used in deferred function call

[danutavadanei]

ineffassign version: last version available go version: go version go1.18.3

Running the linter when interacting with a var after passing it to a deferred function call marks it as ineffectual assignment

package main

import "errors"

func shutdown(err error) {
    if err != nil {
        panic(err)
    }
}

func TestLint() {
    var err error
    defer shutdown(err)

    if true {
        err = errors.New("new error message") // test.go:16:9: ineffectual assignment to err
    }
}

Expectation: should not reported.

Output

ineffassign ./...
go-lint-issue/cmd/test.go:16:9: ineffectual assignment to err

[gordonklaus]

Arguments to a deferred function call are evaluated at the defer statement. Your assignment to err doesn't have the effect that you think it does.

On Fri, Jun 17, 2022, 11:52 Danut Avadanei @.***> wrote:

ineffassign version: last version available go version: go version go1.18.3

Running the linter when interacting with a var after passing it to a deferred function call marks it as ineffectual assignment

package main import "errors" func shutdown(err error) { if err != nil { panic(err) } } func TestLint() { var err error defer shutdown(err)

if true {
    err = errors.New("new error message") // test.go:16:9: ineffectual assignment to err
}

}

Expectation: should not reported.

Output

ineffassign ./... go-lint-issue/cmd/test.go:16:9: ineffectual assignment to err

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[danutavadanei]

Got it, thanks! Fixed my code with defer func() { shutdown(err) }()