slice: negative indexing doesn't panics

[zeslava]

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

$ go version
go version go1.11 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

$ go env
GOARCH="amd64"
GOBIN=""
GOCACHE="/home/slava/.cache/go-build"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="/home/slava/go"
GOPROXY=""
GORACE=""
GOROOT="/home/slava/go1.11"
GOTMPDIR=""
GOTOOLDIR="/home/slava/go1.11/pkg/tool/linux_amd64"
GCCGO="gccgo"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD=""
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-build846395121=/tmp/go-build -gno-record-gcc-switches"

What did you do?

I try to test some code like this

type stack []int

func (s *stack) last() int {
    return (*s)[len(*s)-1]
}

func Test_last(t *testing.T) {
    s := stack{}
    s.last() // should panics
}

What did you expect to see?

panic

What did you see instead?

no panic

[ianlancetaylor]

Please show us a complete standalone example. If you are using go test, use go test -test.v to make sure that your test is being run. Note that a more typical name for a test function would be TestLast.

This Go program panics when I run it:

package main

type stack []int

func (s *stack) last() int {
    return (*s)[len(*s)-1]
}

func last() {
    s := stack{}
    s.last() // should panics
}

func main() {
	last()
}

[bcmills]

Please also test against the most recent patch release: go1.11.4, not go1.11.

[mvdan]

If this is fixed in 1.11.4 and tip, it's very likely just a duplicate of #27289, which was backported into 1.11.1.

[ianlancetaylor]

If you are still having this problem, please show us a complete standalone example. Thanks.

[zeslava]

With go 1.11.4 panic occurs

[ianlancetaylor]

Thanks, so it sounds like this bug has been fixed.

[mvdan]

Well, then it's clearly a duplicate. Thanks for the follow-up.