text/template: Unexpected assignment

[jmooring]

What version of Go are you using (go version)?

go version go1.19.2 linux/amd64

Does this issue reproduce with the latest release?

Yes

What operating system and processor architecture are you using (go env)?

go env Output

GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/jmooring/.cache/go-build"
GOENV="/home/jmooring/.config/go/env"
GOEXE=""
GOEXPERIMENT=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GOMODCACHE="/home/jmooring/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/home/jmooring/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org"
GOROOT="/snap/go/current"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/snap/go/current/pkg/tool/linux_amd64"
GOVCS=""
GOVERSION="go1.19.2"
GCCGO="gccgo"
GOAMD64="v1"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/home/jmooring/code/go-sandbox/go.mod"
GOWORK=""
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOGCCFLAGS="-fPIC -m64 -pthread -Wl,--no-gc-sections -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build3041838949=/tmp/go-build -gno-record-gcc-switches"

What did you do?

This works as expected (stdout is 3):

import (
	"os"
	"text/template"
)

func main() {

	a := [3]int{1, 2, 3}

	t := `
		{{- $x := 0 }}
		{{- $i := 0 }}
		{{- range $i = . }}
		{{- end }}
		{{- $i }}
	`

	tmpl, err := template.New("test").Parse(t)
	if err != nil {
		panic(err)
	}

	err = tmpl.Execute(os.Stdout, a)
	if err != nil {
		panic(err)
	}
}

Now, reverse the order of the first two lines of the template:

import (
	"os"
	"text/template"
)

func main() {

	a := [3]int{1, 2, 3}

	t := `
		{{- $i := 0 }}
		{{- $x := 0 }}
		{{- range $i = . }}
		{{- end }}
		{{- $i }}
	`

	tmpl, err := template.New("test").Parse(t)
	if err != nil {
		panic(err)
	}

	err = tmpl.Execute(os.Stdout, a)
	if err != nil {
		panic(err)
	}
}

Stdout is [1 2 3], but it should be 3.

Same issue with html/template.

[gopherbot]

Change https://go.dev/cl/446795 mentions this issue: text/template: correct assignment, not declaration, in range

[gopherbot]

Change https://go.dev/cl/503575 mentions this issue: text/template: set variables correctly in range assignment

[gopherbot]

Change https://go.dev/cl/503576 mentions this issue: [release-branch.go1.20] text/template: set variables correctly in range assignment