x/tools/gopls: refactor.inline.variable sometimes (erroneously) inlines initial declarations

[adamroyjones]

gopls version

gopls -v version

Build info
----------
golang.org/x/tools/gopls v0.21.0
    golang.org/x/tools/gopls@v0.21.0 h1:k8RlBm3ES+GVe+fbTSkzwKgarmNwN+6aDalb0T0xfag=
    github.com/BurntSushi/toml@v1.5.0 h1:W5quZX/G/csjUnuI8SUYlsHs9M38FC7znL0lIO+DvMg=
    github.com/fatih/camelcase@v1.0.0 h1:hxNvNX/xYBp0ovncs8WyWZrOrpBNub/JfaMvbURyft8=
    github.com/fatih/gomodifytags@v1.17.1-0.20250423142747-f3939df9aa3c h1:dDSgAjoOMp8da3egfz0t2S+t8RGOpEmEXZubcGuc0Bg=
    github.com/fatih/structtag@v1.2.0 h1:/OdNE99OxoI/PqaW/SuSK9uxxT3f/tcSZgon/ssNSx4=
    github.com/fsnotify/fsnotify@v1.9.0 h1:2Ml+OJNzbYCTzsxtv8vKSFD9PbJjmhYF14k/jKC7S9k=
    github.com/google/go-cmp@v0.7.0 h1:wk8382ETsv4JYUZwIsn6YpYiWiBsYLSJiTsyBybVuN8=
    github.com/google/jsonschema-go@v0.3.0 h1:6AH2TxVNtk3IlvkkhjrtbUc4S8AvO0Xii0DxIygDg+Q=
    github.com/modelcontextprotocol/go-sdk@v0.8.0 h1:jdsBtGzBLY287WKSIjYovOXAqtJkP+HtFQFKrZd4a6c=
    github.com/yosida95/uritemplate/v3@v3.0.2 h1:Ed3Oyj9yrmi9087+NczuL5BwkIc4wvTb5zIM+UJPGz4=
    golang.org/x/exp/typeparams@v0.0.0-20251023183803-a4bb9ffd2546 h1:HDjDiATsGqvuqvkDvgJjD1IgPrVekcSXVVE21JwvzGE=
    golang.org/x/mod@v0.30.0 h1:fDEXFVZ/fmCKProc/yAXXUijritrDzahmwwefnjoPFk=
    golang.org/x/sync@v0.18.0 h1:kr88TuHDroi+UVf+0hZnirlk8o8T+4MrK6mr60WkH/I=
    golang.org/x/sys@v0.38.0 h1:3yZWxaJjBmCWXqhN1qh02AkOnCQ1poK6oF+a7xWL6Gc=
    golang.org/x/telemetry@v0.0.0-20251111182119-bc8e575c7b54 h1:E2/AqCUMZGgd73TQkxUMcMla25GB9i/5HOdLr+uH7Vo=
    golang.org/x/text@v0.31.0 h1:aC8ghyu4JhP8VojJ2lEHBnochRno1sgL6nEi9WGFGMM=
    golang.org/x/tools@v0.39.1-0.20251205192105-907593008619 h1:NIdx9X+Z8lIV89t3Bs/bb4D/KTtHP4KYdUIFMiGlo6Y=
    golang.org/x/vuln@v1.1.4 h1:Ju8QsuyhX3Hk8ma3CesTbO8vfJD9EvUBgHvkxHBzj0I=
    honnef.co/go/tools@v0.7.0-0.dev.0.20251022135355-8273271481d0 h1:5SXjd4ET5dYijLaf0O3aOenC0Z4ZafIWSpjUzsQaNho=
    mvdan.cc/gofumpt@v0.8.0 h1:nZUCeC2ViFaerTcYKstMmfysj6uhQrA2vJe+2vwGU6k=
    mvdan.cc/xurls/v2@v2.6.0 h1:3NTZpeTxYVWNSokW3MKeyVkz/j7uYXYiMtXRUfmjbgI=
go: go1.26.0

go env

go env

AR='ar'
CC='gcc'
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_ENABLED='1'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
CXX='g++'
GCCGO='gccgo'
GO111MODULE=''
GOAMD64='v1'
GOARCH='amd64'
GOAUTH='netrc'
GOBIN=''
GOCACHE='/home/adamjones/.cache/go-build'
GOCACHEPROG=''
GODEBUG=''
GOENV='/home/adamjones/.config/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFIPS140='off'
GOFLAGS=''
GOGCCFLAGS='-fPIC -m64 -pthread -Wl,--no-gc-sections -fmessage-length=0 -ffile-prefix-map=/tmp/go-build4236351802=/tmp/go-build -gno-record-gcc-switches'
GOHOSTARCH='amd64'
GOHOSTOS='linux'
GOINSECURE=''
GOMOD='/home/adamjones/tmp/reprex-inlining-bug/go.mod'
GOMODCACHE='/home/adamjones/.local/share/go/pkg/mod'
GONOPROXY='github.com/unravelin'
GONOSUMDB='github.com/unravelin'
GOOS='linux'
GOPATH='/home/adamjones/.local/share/go'
GOPRIVATE='github.com/unravelin'
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/home/adamjones/.local/share/go/pkg/mod/golang.org/toolchain@v0.0.1-go1.26.0.linux-amd64'
GOSUMDB='sum.golang.org'
GOTELEMETRY='local'
GOTELEMETRYDIR='/home/adamjones/.config/go/telemetry'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/home/adamjones/.local/share/go/pkg/mod/golang.org/toolchain@v0.0.1-go1.26.0.linux-amd64/pkg/tool/linux_amd64'
GOVCS=''
GOVERSION='go1.26.0'
GOWORK=''
PKG_CONFIG='pkg-config'

What did you do?

package main

import (
	"fmt"
)

func main() {
	f()
}

func f() {
	s := "bread does not nourish me"
	{
		s = "dawn disrupts me, all day"
		g(s)
	}
}

func g(s string) {
	fmt.Println(s)
}

I then attempted to inline s in the call to g (line 15).

What did you see happen?

gopls codeaction -kind refactor.inline.variable -exec main.go:15:6

prints out

package main

import (
	"fmt"
)

func main() {
	f()
}

func f() {
	s := "bread does not nourish me"
	{
		s = "dawn disrupts me, all day"
		g("bread does not nourish me")
	}
}

func g(s string) {
	fmt.Println(s)
}

What did you expect to see?

I expected it to inline the value "dawn disrupts me, all day".

I also noticed that gopls codeaction -h doesn't show refactor.inline.variable as a possible code action. (I fished it out from eglot's buffer in Emacs to produce a command-line reproduction.)

Editor and settings

GNU Emacs 30.1 with eglot, but I can reproduce things with the CLI (see above).

Logs

I'm happy to capture them if needed.

[gabyhelp]

Related Issues

• x/tools/gopls: gopls panics/crashes on inline variable #76144 (closed)
• x/tools/gopls: Extract Function: incorrect transformation of free "goto" continuation #77157 (closed)
• x/tools/internal/refactor/inline: nil deref in (*freeVisitor).declare #73321
• x/tools/gopls: `//go:fix inline` is very slow to compute fixes (excessive scans of Info.Uses and re-formatting/parsing of whole file) #75773 (closed)
• x/tools/gopls: Inline: panic in falcon analysis (unexpected core type) #74393 (closed)
• x/tools/gopls: Feature Request: Support for "Inline Method" refactoring code action #59243 (closed)
• x/tools/gopls: add refactor.inline.variable-all code action #70085
• x/tools/gopls/internal/golang: inline variable: nil panic in inlineVariableOne #74347 (closed)
• x/tools/gopls: refactor.rewrite.removeUnusedParam: avoid literalization for recursive spread call #70554
• x/tools/gopls: extract function with `goto` leaves out `:` #77156 (closed)

_{(Emoji vote if this was helpful or unhelpful; more detailed feedback welcome in this discussion.)}

[adonovan]

I agree this is a bug, but the fix may be involved. Strictly, the refactoring needs to prove that a single definition of s reaches the call g(s), but this requires dataflow analysis or SSA.

What do people ordinarily expect an IDE to do in the case below, where f might set s to some third value such as "Silent and starving, I prowl through the streets"?

	s := "bread does not nourish me"
	{
		s = "dawn disrupts me, all day"
		f(&s)
		g(s)
	}

[adamroyjones]

Thanks for the quick response—I'm not sure what people would expect!

My own expectations are very open, given the limits of analysis. I treat the code actions as fortunate offerings and I'm not surprised, or disappointed, if they're sometimes unavailable. In this case, if a quick proof can't be found, or if references seep out as in the f(&s) case, etc., I think a quiet denial would be fair.

I'll ask internally in our company for their opinions.

[adamroyjones]

Only one person responded to my internal question. Their opinion was roughly the same as mine: they wouldn't expect the IDE to provide the option. (Others may've thought that it was a kind of trick question. 😓)

[adamroyjones]

A colleague (@igorrohal 👋🏻) just let me know about GoLand's behaviour. (I think GoLand doesn't rely on any of the x/tools (etc.) machinery.)

In both cases (with and without f(&s)), GoLand refuses to act with the message

Cannot perform refactoring. Variable is reassigned

It also produced this interesting transformation:

s := "bread does not nourish me"
{
	f(&s)
	g(s)
}

is transformed to

{
	f(&("bread does not nourish me"))
	g("bread does not nourish me")
}

which is invalid (but, even if it were valid, it'd have the wrong semantics).