testing: inconsistent coverage on anonymous functions in slice #73939
Description
Go version
go version go1.24.3 darwin/arm64
Output of go env in your module/workspace:
AR='ar'
CC='clang'
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_ENABLED='1'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
CXX='clang++'
GCCGO='gccgo'
GO111MODULE=''
GOARCH='arm64'
GOARM64='v8.0'
GOAUTH='netrc'
GOBIN=''
GOCACHE='/Users/rob/Library/Caches/go-build'
GOCACHEPROG=''
GODEBUG=''
GOENV='/Users/rob/Library/Application Support/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFIPS140='off'
GOFLAGS=''
GOGCCFLAGS='-fPIC -arch arm64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -ffile-prefix-map=/var/folders/ry/6bttgkt51f14fhb1cwsg_6r00000gp/T/go-build1866195821=/tmp/go-build -gno-record-gcc-switches -fno-common'
GOHOSTARCH='arm64'
GOHOSTOS='darwin'
GOINSECURE=''
GOMOD='/Users/rob/Sandbox/covertest/go.mod'
GOMODCACHE='/Users/rob/.local/share/go/pkg/mod'
GONOPROXY=''
GONOSUMDB=''
GOOS='darwin'
GOPATH='/Users/rob/.local/share/go'
GOPRIVATE=''
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/Users/rob/.local/share/mise/installs/go/1.24.3'
GOSUMDB='sum.golang.org'
GOTELEMETRY='local'
GOTELEMETRYDIR='/Users/rob/Library/Application Support/go/telemetry'
GOTMPDIR=''
GOTOOLCHAIN='auto'
GOTOOLDIR='/Users/rob/.local/share/mise/installs/go/1.24.3/pkg/tool/darwin_arm64'
GOVCS=''
GOVERSION='go1.24.3'
GOWORK=''
PKG_CONFIG='pkg-config'What did you do?
cover.go:
package covertest
func run() error {
runFuncs := []func() error{
func() error { return nil },
func() error { return nil },
func() error { return nil },
}
for _, f := range runFuncs {
if err := f(); err != nil {
return err
}
}
return nil
}cover_test.go:
package covertest
import "testing"
func Test_run(t *testing.T) {
if err := run(); err != nil {
t.Fatal(err)
}
}go test -coverprofile=profile.cov
go tool cover -html=profile.covWhat did you see happen?
Coverage reporting for the first anonymous function declaration is different from the next two, despite them having the same coverage.
It appears to include the function signature only if it is the first element of the slice.
profile.cov:
mode: set
example.com/covertest/cover.go:3.18,5.16 1 1
example.com/covertest/cover.go:5.16,5.30 1 1
example.com/covertest/cover.go:6.16,6.30 1 1
example.com/covertest/cover.go:7.16,7.30 1 1
example.com/covertest/cover.go:10.2,10.29 1 1
example.com/covertest/cover.go:10.29,11.29 1 1
example.com/covertest/cover.go:11.29,13.4 1 0
example.com/covertest/cover.go:16.2,16.12 1 1
What did you expect to see?
I would expect that the function signature of the anonymous functions, which in this case would be:
func() errorto either be reported as "green" across all 3 slice elements, or to not be reported across any slice elements. Either behavior seems justifiable, but I would expect it to be consistent.