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

$ go version
go version go1.17 linux/amd64

Does this issue reproduce with the latest release?

Yes, it used to compile on go 1.16

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

$ go env
GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/user/.cache/go-build"
GOENV="/home/user/.config/go/env"
GOEXE=""
GOEXPERIMENT=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GOMODCACHE="/home/user/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/home/user/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/home/user/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/home/user/go/pkg/tool/linux_amd64"
GOVCS=""
GOVERSION="go1.17"
GCCGO="gccgo"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/dev/null"
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 -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build3898192828=/tmp/go-build -gno-record-gcc-switches"

What did you do?

The code and playground links are below.

If I remove the if true {} block the code compiles.

https://play.golang.org/p/hegRGlzb751

package main

import (
	"fmt"
	"strings"
)

type app struct {
	Name string
}

func bug() func() {
	return func() {


		// the issue is this if true block
		if true {
			return
		}

		var xx = []app{}
		var gapp app
		for _, app := range xx {
			if strings.ToUpper("") == app.Name {
				fmt.Printf("%v\n", app)
				gapp = app
			}
		}
		fmt.Println(gapp)
	}
}

func main() {
	bug()
}

What did you expect to see?

A function that immediately returns
A compiled application.

What did you see instead?

A compiler bug.

# command-line-arguments
./test.go:21:10: internal compiler error: unexpected Defn: 
.   RANGE-init
.   .   DCL # test.go:21
.   .   .   NAME-main.app tc(1) Class:PAUTO Offset:0 OnStack Used main.app # test.go:21
.   RANGE tc(1) Def # test.go:21
.   .   NAME-main.xx tc(1) Class:PAUTO Offset:0 OnStack Used SLICE-[]app # test.go:19
.   RANGE-Key
.   .   NAME-main._ tc(1) Offset:0 blank
.   .   NAME-main.app tc(1) Class:PAUTO Offset:0 OnStack Used main.app # test.go:21
.   RANGE-Body
.   .   IF tc(1) # test.go:22
.   .   IF-Cond
.   .   .   EQ tc(1) bool # test.go:22 bool
.   .   .   .   CALLFUNC tc(1) Use:1 string # test.go:22 string
.   .   .   .   .   NAME-strings.ToUpper tc(1) Class:PFUNC Offset:0 Used FUNC-func(string) string # strings.go:550
.   .   .   .   CALLFUNC-Args
.   .   .   .   .   LITERAL-"" tc(1) string # test.go:22
.   .   .   .   DOT tc(1) string # test.go:22 main.Name string
.   .   .   .   .   NAME-main.app tc(1) Class:PAUTO Offset:0 OnStack Used main.app # test.go:21
.   .   IF-Body
.   .   .   CALLFUNC tc(1) Use:3 STRUCT-(int, error) # test.go:23 STRUCT-(int, error)
.   .   .   .   NAME-fmt.Printf tc(1) Class:PFUNC Offset:0 Used FUNC-func(string, ...interface {}) (int, error) # print.go:212
.   .   .   CALLFUNC-Args
.   .   .   .   LITERAL-"%v\n" tc(1) string # test.go:23
.   .   .   .   CONVIFACE tc(1) Implicit INTER-interface {} # test.go:23 INTER-interface {}
.   .   .   .   .   NAME-main.app tc(1) Class:PAUTO Offset:0 OnStack Used main.app # test.go:21
.   .   .   AS tc(1) # test.go:24
.   .   .   .   NAME-main.gapp tc(1) Class:PAUTO Offset:0 OnStack Used main.app # test.go:20
.   .   .   .   NAME-main.app tc(1) Class:PAUTO Offset:0 OnStack Used main.app # test.go:21

Please file a bug report including a short program that triggers the error.
https://golang.org/issue/new