Golang cmd/gofmt: inconsistent behavior on removing unnecessary type names with -s arg

Go version

go version go1.21.5 linux/amd64

Output of go env in your module/workspace:

GO111MODULE=''
GOARCH='amd64'
GOBIN=''
GOCACHE='/home/fishy/.cache/go-build'
GOENV='/home/fishy/.config/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFLAGS=''
GOHOSTARCH='amd64'
GOHOSTOS='linux'
GOINSECURE=''
GOMODCACHE='/home/fishy/.gopath/pkg/mod'
GONOPROXY='omitted'
GONOSUMDB='omitted'
GOOS='linux'
GOPATH='/home/fishy/.gopath'
GOPRIVATE='omitted'
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/usr/lib/go-1.21'
GOSUMDB='sum.golang.org'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/usr/lib/go-1.21/pkg/tool/linux_amd64'
GOVCS=''
GOVERSION='go1.21.5'
GCCGO='gccgo'
GOAMD64='v1'
AR='ar'
CC='gcc'
CXX='g++'
CGO_ENABLED='1'
GOMOD='/home/fishy/test/go.mod'
GOWORK=''
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
PKG_CONFIG='pkg-config'
GOGCCFLAGS='-fPIC -m64 -pthread -Wl,--no-gc-sections -fmessage-length=0 -ffile-prefix-map=/tmp/go-build1401412523=/tmp/go-build -gno-record-gcc-switches'

What did you do?

main.go:

package main

import (
    "fmt"
)

type Data struct {
    Foo int
}

type Response struct {
    Item  []*Data
    Items [][]*Data
}

var s = Response{
    Item: []*Data{
        &Data{
            Foo: 1,
        },
    },
    Items: [][]*Data{
        {
            &Data{
                Foo: 2,
            },
            &Data{
                Foo: 3,
            },
        },
    },
}

func main() {
    fmt.Println(s)
}

gofmt -s -d main.go will only suggest removing &Data from Item, but not from Items:

$ gofmt -s -d main.go
diff main.go.orig main.go
--- main.go.orig
+++ main.go
@@ -15,7 +15,7 @@

 var s = Response{
        Item: []*Data{
-               &Data{
+               {
                        Foo: 1,
                },
        },

But removing both are perfectly fine: https://go.dev/play/p/pEfXLBwuwL1

What did you see happen?

gofmt -s is inconsistent as it fail to suggest the same thing when it's under two or more layers of slices.

What did you expect to see?

gofmt -s being consistent.

Comment From: dmitshur

CC @griesemer, @mvdan.

Comment From: griesemer

Assigning to me for 1.24 to make it visible.

Comment From: griesemer

Not urgent - we have lived with this for > 15 years. Good, isolated project for somebody who is well-versed with the AST.

Comment From: iamrajhans

@griesemer May I take on this issue? Additionally, could you kindly provide guidance on the resolution? Thank you.

Comment From: mvdan

You can give this issue a try, yes. I can give some guidance, but it is assumed that whoever tries with issues like these will do most of the legwork by themselves.

Comment From: vikramcse

@mvdan I am giving this issue a try, can you please assign to me

Comment From: gopherbot

Change https://go.dev/cl/641956 mentions this issue: cmd/gofmt: Handle nested array/slice of pointers

Comment From: vikramcse

Hello @dmitshur

If possiblem can you please review the CL: https://go.dev/cl/641956

Thanks

Comment From: vikramcse

Hello @griesemer

can you please review the CL: https://go.dev/cl/641956

Thanks

Comment From: vikramcse

Hello @griesemer Is there something pending in this CL to get it reviewed?

cc: @ianlancetaylor

Comment From: griesemer

@vikramcse It's on my list but it's not urgent.

Comment From: vikramcse

Hello @griesemer If anything needs to be done for this CL, I will be up for it Thanks