Golang x/tools/gopls/internal/analysis/modernize: slicescontains analyzer suggests invalid refactoring when function parameter type doesn't match slice element type

Go version

go1.24.3

Output of go env in your module/workspace:

AR='ar'
CC='cc'
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_ENABLED='1'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
CXX='c++'
GCCGO='gccgo'
GO111MODULE=''
GOARCH='arm64'
GOARM64='v8.0'
GOAUTH='netrc'
GOBIN='/Users/mac/go/bin'
GOCACHE='/Users/mac/Library/Caches/go-build'
GOCACHEPROG=''
GODEBUG=''
GOENV='/Users/mac/Library/Application Support/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFIPS140='off'
GOFLAGS=''
GOGCCFLAGS='-fPIC -arch arm64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -ffile-prefix-map=/var/folders/tq/m955dwkd1519phkp2hwpv9_80000gn/T/go-build2400307511=/tmp/go-build -gno-record-gcc-switches -fno-common'
GOHOSTARCH='arm64'
GOHOSTOS='darwin'
GOINSECURE=''
GOMOD='/dev/null'
GOMODCACHE='/Users/mac/go/pkg/mod'
GONOPROXY=''
GONOSUMDB=''
GOOS='darwin'
GOPATH='/Users/mac/go'
GOPRIVATE=''
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/usr/local/go'
GOSUMDB='sum.golang.org'
GOTELEMETRY='local'
GOTELEMETRYDIR='/Users/mac/Library/Application Support/go/telemetry'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/usr/local/go/pkg/tool/darwin_arm64'
GOVCS=''
GOVERSION='go1.24.3'
GOWORK=''
PKG_CONFIG='pkg-config'

What did you do?

package main

import "fmt"

type Expression interface{}

type Column struct {
    UniqueID int64
}

func (col *Column) EqualColumn(expr Expression) bool {
    other, ok := expr.(*Column)
    if !ok {
        return false
    }
    return col.UniqueID == other.UniqueID
}

func (col *Column) InColumnArray(cols []*Column) bool {
    for _, c := range cols {
        if col.EqualColumn(c) { // c is *Column, but EqualColumn expects Expression
            return true
        }
    }
    return false
}

func main() {

    cols := []*Column{
        {UniqueID: 1},
        {UniqueID: 2},
        {UniqueID: 3},
    }
    colToCheck := &Column{UniqueID: 2}
    fmt.Println("Is column in array?", colToCheck.InColumnArray(cols)) // true

    colToCheck2 := &Column{UniqueID: 5}
    fmt.Println("Is column in array?", colToCheck2.InColumnArray(cols)) // false
}

The Output:

Is column in array? true
Is column in array? false

What did you see happen?

After executing modernize -fix -test ./..., it will become.

package main

import "slices"

import "fmt"

type Expression interface{}

type Column struct {
    UniqueID int64
}

func (col *Column) EqualColumn(expr Expression) bool {
    other, ok := expr.(*Column)
    if !ok {
        return false
    }
    return col.UniqueID == other.UniqueID
}

func (col *Column) InColumnArray(cols []*Column) bool {
    return slices.ContainsFunc(cols, col.EqualColumn)
}

func main() {

    cols := []*Column{
        {UniqueID: 1},
        {UniqueID: 2},
        {UniqueID: 3},
    }
    colToCheck := &Column{UniqueID: 2}
    fmt.Println("Is column in array?", colToCheck.InColumnArray(cols)) // true

    colToCheck2 := &Column{UniqueID: 5}
    fmt.Println("Is column in array?", colToCheck2.InColumnArray(cols)) // false
}

Output:

# command-line-arguments
./main2.go:22:28: in call to slices.ContainsFunc, S (type []*Column) does not satisfy ~[]E

What did you expect to see?

Do not take action on this situation.

Comment From: gopherbot

Change https://go.dev/cl/693879 mentions this issue: gopls/internal/analysis/modernize: fix the compilation error caused

Comment From: gabyhelp

Related Issues

• x/tools/gopls/internal/analysis/modernize: slicescontains offers fix that elides an implicit interface conversion #73564 (closed)
• x/tools/gopls/internal/analysis/modernize: the conversion of variadic functions to `slices.ContainsFunc` causes type errors #73269 (closed)
• x/tools/gopls/internal/analysis/modernize: append([]T{}, x...) -> slices.Clone(x) fix may unsoundly return nil #73557 (closed)
• x/tools/gopls/internal/analysis/modernize: rangeint produces invalid syntax due to use of types.RelativeTo #74687
• x/tools/gopls/internal/analyzer/modernize: bug in slices.Contains transformation #71313 (closed)
• x/tools/gopls/internal/analysis/modernize: Panic in modernize/sortslice.go #71786 (closed)
• x/tools/gopls/internal/analysis/modernize: rangeint generates correct but not idiomatic transformation #71725 (closed)

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