cmd/compile: internal compiler error: unexpected stmt: nil

[LukeShu]

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

$ go version
go version go1.17.5 linux/amd64

Does this issue reproduce with the latest release?

Yes, 1.17.5 is the latest release.

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

go env Output

$ go env
GO111MODULE=""
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/lukeshu/.cache/go-build"
GOENV="/home/lukeshu/.config/go/env"
GOEXE=""
GOEXPERIMENT=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOINSECURE=""
GOMODCACHE="/home/lukeshu/go/pkg/mod"
GONOPROXY=""
GONOSUMDB=""
GOOS="linux"
GOPATH="/home/lukeshu/go"
GOPRIVATE=""
GOPROXY="https://proxy.golang.org,direct"
GOROOT="/usr/lib/go"
GOSUMDB="sum.golang.org"
GOTMPDIR=""
GOTOOLDIR="/usr/lib/go/pkg/tool/linux_amd64"
GOVCS=""
GOVERSION="go1.17.5"
GCCGO="gccgo"
AR="ar"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/home/lukeshu/src/github.com/datawire/pyc-dis/go.mod"
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=/run/user/1000/tmpdir/go-build1874362547=/tmp/go-build -gno-record-gcc-switches"

What did you do?

https://go.dev/play/p/W8yLp8Nstp-

What did you expect to see?

./prog.go:20:3: nil evaluated but not used

Go build failed.

What did you see instead?

./prog.go:18:2: internal compiler error: unexpected stmt: nil

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

Go build failed.

[ianlancetaylor]

This gets an internal compiler error on 1.17 but works on tip (works in the sense that the compiler reports the error "nil is not used"). Since this is invalid code, and this is fixed on tip, and the error is not so bad in 1.17, I'm not sure it's worth backporting a fix. Happy to hear other opinions.

[dmitshur]

Since this issue is resolved on tip, I'll move it to that milestone and close it as fixed. It can still be considered for backport to 1.17 and 1.16 (if 1.16 is affected), but I do not think it would meet the bar for the reasons Ian described. Thank you for reporting it, though.