cmd/vet: go vet failing in directory with cgo and no tests

[variadico]

Please answer these questions before submitting your issue. Thanks!

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

go version go1.10 darwin/amd64 on macOS 10.13.3.

Does this issue reproduce with the latest release?

This issue does not happen with 1.9.4, only 1.10.

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

GOARCH="amd64"
GOBIN=""
GOCACHE="/Users/jaime/Library/Caches/go-build"
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOOS="darwin"
GOPATH="/Users/jaime/go"
GORACE=""
GOROOT="/usr/local/Cellar/go/1.10/libexec"
GOTMPDIR=""
GOTOOLDIR="/usr/local/Cellar/go/1.10/libexec/pkg/tool/darwin_amd64"
GCCGO="gccgo"
CC="clang"
CXX="clang++"
CGO_ENABLED="1"
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 -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/x8/d_hkkg0977n90n6ml16tnqlr0000gn/T/go-build981458154=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

I created a package that uses cgo. In that package, I call a function defined in a .h file. Then, I ran go vet on that package.

// bar.go
package bar

/*
#import "bar.h"
*/
import "C"

func Bar() {
	C.bar()
}

// bar.h
int bar() {
	return 42;
}

I've created an isolated example at this repo: https://github.com/variadico/vetbug

What did you expect to see?

go vet should have analyzed the Go source files and reported no errors.

What did you see instead?

go vet failed to run, saying there are no Go source files.

[ysmolski]

This was introduced in CL cebc706, https://go-review.googlesource.com/87636
/cc @ianlancetaylor

[gopherbot]

Change https://golang.org/cl/99175 mentions this issue: cmd/go: run vet on packages with only cgo files

[ianlancetaylor]

Reopening for 1.10.1.

[andybons]

CL 99175 OK for Go 1.10.1

[gopherbot]

Change https://golang.org/cl/102785 mentions this issue: [release-branch.go1.10] cmd/go: run vet on packages with only cgo files