Description
What version of Go are you using (go version)?
$ go version go version devel +2ff33f5e44 Thu Dec 17 16:03:19 2020 +0000 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 go version devel +2ff33f5e44 Thu Dec 17 16:03:19 2020 +0000 linux/amd64 GO111MODULE="on" GOARCH="amd64" GOBIN="/home/user/bin" GOCACHE="/home/user/.cache/go-build" GOENV="/home/user/.config/go/env" GOEXE="" GOFLAGS="" GOHOSTARCH="amd64" GOHOSTOS="linux" GOINSECURE="" GOMODCACHE="/home/user/pkg/mod" GONOPROXY="" GONOSUMDB="" GOOS="linux" GOPATH="/home/user" GOPRIVATE="" GOPROXY="https://proxy.golang.org,direct" GOROOT="/home/user/go" GOSUMDB="sum.golang.org" GOTMPDIR="" GOTOOLDIR="/home/user/go/pkg/tool/linux_amd64" GOVCS="" GOVERSION="devel +2ff33f5e44 Thu Dec 17 16:03:19 2020 +0000" GCCGO="gccgo" AR="ar" CC="gcc" CXX="g++" CGO_ENABLED="1" GOMOD="/dev/null" 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-build3281173737=/tmp/go-build -gno-record-gcc-switches"
What did you do?
~/src/gonum.org/v1/gonum/graph/topo$ go vet
gonum.org/v1/gonum/graph/topo_test
./2sat_example_test.go:177:1: ExampleTarjanSCC_2sat refers to unknown field or method: TarjanSCC.2sat
However, godoc renders the 2sat example.
What did you expect to see?
An error from vet and a failure from godoc to render the example or no error from vet and a godoc rendering of the example.
What did you see instead?
A vet error but a rendered example. See for example the godoc.org page here (note that pkg.go.dev does not render this example).
What would you like to see?
No error and a rendered example. That is, a relaxation of the documented requirement for an initial lowercase letter in the suffix ("The suffix must start with a lower-case letter.") to allow numeric leading glyphs.
Additional information
This is a repeat of #27442 which was closed into #23864 with comments there that this motivating issue would be considered in the fix. The change that that issue links to does not fix this problem consistently (local godoc does render the example, godoc.org also, but — in my view unreasonably stricly — pkg.go.dev does not). The documentation does say "The suffix must start with a lower-case letter." However given the rationale for that being a way of disambiguating methods' examples (which must start with an uppercase due to language rules) the requirement seems overly strict; it could be anything that is not a method, that is !uppercase as stated here.
/cc @dmitshur