x/tools/gopls: range over func without variable shows 'simplify range expression' warning

[k3forx]

gopls version

golang.org/x/tools/gopls v0.14.2 golang.org/x/tools/gopls@v0.14.2 h1:sIw6vjZiuQ9S7s0auUUkHlWgsCkKZFWDHmrge8LYsnc= github.com/BurntSushi/toml@v1.2.1 h1:9F2/+DoOYIOksmaJFPw1tGFy1eDnIJXg+UHjuD8lTak= github.com/google/go-cmp@v0.5.9 h1:O2Tfq5qg4qc4AmwVlvv0oLiVAGB7enBSJ2x2DqQFi38= github.com/sergi/go-diff@v1.1.0 h1:we8PVUC3FE2uYfodKH/nBHMSetSfHDR6scGdBi+erh0= golang.org/x/exp/typeparams@v0.0.0-20221212164502-fae10dda9338 h1:2O2DON6y3XMJiQRAS1UWU+54aec2uopH3x7MAiqGW6Y= golang.org/x/mod@v0.14.0 h1:dGoOF9QVLYng8IHTm7BAyWqCqSheQ5pYWGhzW00YJr0= golang.org/x/sync@v0.4.0 h1:zxkM55ReGkDlKSM+Fu41A+zmbZuaPVbGMzvvdUPznYQ= golang.org/x/sys@v0.14.0 h1:Vz7Qs629MkJkGyHxUlRHizWJRG2j8fbQKjELVSNhy7Q= golang.org/x/telemetry@v0.0.0-20231114163143-69313e640400 h1:brbkEFfGwNGAEkykUOcryE/JiHUMMJouzE0fWWmz/QU= golang.org/x/text@v0.13.0 h1:ablQoSUd0tRdKxZewP80B+BaqeKJuVhuRxj/dkrun3k= golang.org/x/tools@v0.14.1-0.20231114185516-c9d3e7de13fd h1:Oku7E+OCrXHyst1dG1z10etCTxewCHXNFLRlyMPbh3w= golang.org/x/vuln@v1.0.1 h1:KUas02EjQK5LTuIx1OylBQdKKZ9jeugs+HiqO5HormU= honnef.co/go/tools@v0.4.5 h1:YGD4H+SuIOOqsyoLOpZDWcieM28W47/zRO7f+9V3nvo= mvdan.cc/gofumpt@v0.4.0 h1:JVf4NN1mIpHogBj7ABpgOyZc65/UUOkKQFkoURsz4MM= mvdan.cc/xurls/v2@v2.4.0 h1:tzxjVAj+wSBmDcF6zBB7/myTy3gX9xvi8Tyr28AuQgc= go: go1.22.0

go env

❯ go env
GO111MODULE='on'
GOARCH='amd64'
GOBIN=''
GOCACHE='/Users/kanatamiyahana/Library/Caches/go-build'
GOENV='/Users/kanatamiyahana/Library/Application Support/go/env'
GOEXE=''
GOEXPERIMENT='rangefunc'
GOFLAGS=''
GOHOSTARCH='amd64'
GOHOSTOS='darwin'
GOINSECURE=''
GOMODCACHE='/Users/kanatamiyahana/go/pkg/mod'
GONOPROXY=''
GONOSUMDB=''
GOOS='darwin'
GOPATH='/Users/kanatamiyahana/go'
GOPRIVATE=''
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/Users/kanatamiyahana/.asdf/installs/golang/1.22.0/go'
GOSUMDB='sum.golang.org'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/Users/kanatamiyahana/.asdf/installs/golang/1.22.0/go/pkg/tool/darwin_amd64'
GOVCS=''
GOVERSION='go1.22.0'
GCCGO='gccgo'
GOAMD64='v1'
AR='ar'
CC='clang'
CXX='clang++'
CGO_ENABLED='1'
GOMOD='/Users/kanatamiyahana/repos/snkrdunk.com/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 -arch x86_64 -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -ffile-prefix-map=/var/folders/fn/jml4l1qs6q32rndh73fcqptc0000gn/T/go-build3540065755=/tmp/go-build -gno-record-gcc-switches -fno-common'

What did you do?

I wrote the following program.

package main

type Seq[V any] func(yield func(V) bool)

func main() {
	var seq Seq[int] = func(yield func(int) bool) {
		for i := range 5 {
			yield(i)
		}
	}

	for _ = range seq {
		println("Hello, World!")
	}
}

What did you see happen?

I got the warning from gopls.

❯ gopls check ./main.go
/Users/kanatamiyahana/repos/scrap/go1.22/main.go:12:6-7: simplify range expression

If I re-write the code like below, then I get the another error ./main.go:12:12: cannot range over seq (variable of type Seq[int])

package main

type Seq[V any] func(yield func(V) bool)

func main() {
	var seq Seq[int] = func(yield func(int) bool) {
		for i := range 5 {
			yield(i)
		}
	}

	for range seq { // cannot range over seq (variable of type Seq[int])
		println("Hello, World!")
	}
}

What did you expect to see?

I expect to get no warning.

Editor and settings

Here is my VSCode settings. I only pasted Go related settings.

  "[go]": {
    "editor.insertSpaces": false,
    "editor.defaultFormatter": "golang.go"
  },
  "go.goroot": "/Users/kanatamiyahana/.asdf/installs/golang/1.22.0/go",
  "go.gopath": "/Users/kanatamiyahana/go",
  "gopls": {
    "buildFlags": ["-tags=parallel,serial,integration"]
  },

Logs

No response

[hyangah]

I think this is an interesting consequences between the simplifyrange analyzer and the inconsistency discussed in #65236
Depending on how issue 65236 is resolved, it looks like we also need to adjust the analyzer and also gofmt -s.

[findleyr]

Deduping to #67239, which is more general.