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

$ go version
go version go1.12.2 linux/amd64
$ go list -m golang.org/x/tools
golang.org/x/tools v0.0.0-20190406165526-0d5674b3111a

Does this issue reproduce with the latest release?

Yes

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

$ go env
GOARCH="amd64"
GOBIN="/home/myitcv/gostuff/src/github.com/myitcv/govim/cmd/govim/.bin"
GOCACHE="/home/myitcv/.cache/go-build"
GOEXE=""
GOFLAGS=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="/home/myitcv/gostuff"
GOPROXY=""
GORACE=""
GOROOT="/home/myitcv/gos"
GOTMPDIR=""
GOTOOLDIR="/home/myitcv/gos/pkg/tool/linux_amd64"
GCCGO="gccgo"
CC="gcc"
CXX="g++"
CGO_ENABLED="1"
GOMOD="/home/myitcv/gostuff/src/github.com/myitcv/govim/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=/tmp/go-build316650147=/tmp/go-build -gno-record-gcc-switches"

What did you do?

Considering the following govim testscript in which I attempt a completion in a file that does not completely type-check:

vim ex 'e main.go'
vim ex 'call cursor(5,1)'
vim ex 'call feedkeys(\"A\\<C-X>\\<C-O>\", \"x\")'

-- go.mod --
module mod.com

-- main.go --
package main

func main() {
	cmd := exec.Command("ls")
	out, err := cmd.
}

What did you expect to see?

I think I would expect this call to simply return zero results, i.e. for there to be no completion candidates.

What did you see instead?

An error returned by gopls:

cannot resolve cmd

The reason I think this is wrong is that I'm otherwise unclear how we would distinguish between a more fundamental, low-level error and the case of there simply being no completions because of either a type-check error/some other reason.

But very much look to @stamblerre and @ianthehat for their thoughts on what is right/wrong here.