cmd/compile: better error message when import embed package

Fixes #73955

Change-Id: I7cf3ab4c70dc2e2765b54b88ae8cfc77a3073344
Reviewed-on: https://go-review.googlesource.com/c/go/+/678355
Auto-Submit: Robert Griesemer <gri@google.com>
Reviewed-by: Carlos Amedee <carlos@golang.org>
Reviewed-by: Robert Griesemer <gri@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

diff --git a/src/cmd/compile/internal/noder/noder.go b/src/cmd/compile/internal/noder/noder.go
index 77daf9eda59085239afa546ce4607c5ec3c4e451..79a907833360309930b5e028c4b34c40e5b738bb 100644 (file)
--- a/src/cmd/compile/internal/noder/noder.go
+++ b/src/cmd/compile/internal/noder/noder.go
@@ -458,7 +458,7 @@ func Renameinit() *types.Sym {
 func checkEmbed(decl *syntax.VarDecl, haveEmbed, withinFunc bool) error {
        switch {
        case !haveEmbed:
-               return errors.New("go:embed only allowed in Go files that import \"embed\"")
+               return errors.New("go:embed requires import \"embed\" (or import _ \"embed\", if package is not used)")
        case len(decl.NameList) > 1:
                return errors.New("go:embed cannot apply to multiple vars")
        case decl.Values != nil: