cmd/go: fix import current directory error message

Fixes #14683

Change-Id: I62c429e4fcc2f20a94d3db8c1f0ca587252c07a7
Reviewed-on: https://go-review.googlesource.com/c/go/+/174130
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/cmd/go/go_test.go

@@ -3626,7 +3626,7 @@ func TestImportLocal(t *testing.T) {
 		var _ = x.X
 	`)
 	tg.runFail("build", "dir/x")
-	tg.grepStderr("local import.*in non-local package", "did not diagnose local import")
+	tg.grepStderr("cannot import current directory", "did not diagnose import current directory")
 
 	// ... even in a test.
 	tg.tempFile("src/dir/x/xx.go", `package x
@@ -3639,7 +3639,7 @@ func TestImportLocal(t *testing.T) {
 	`)
 	tg.run("build", "dir/x")
 	tg.runFail("test", "dir/x")
-	tg.grepStderr("local import.*in non-local package", "did not diagnose local import")
+	tg.grepStderr("cannot import current directory", "did not diagnose import current directory")
 
 	// ... even in an xtest.
 	tg.tempFile("src/dir/x/xx.go", `package x
@@ -3652,7 +3652,7 @@ func TestImportLocal(t *testing.T) {
 	`)
 	tg.run("build", "dir/x")
 	tg.runFail("test", "dir/x")
-	tg.grepStderr("local import.*in non-local package", "did not diagnose local import")
+	tg.grepStderr("cannot import current directory", "did not diagnose import current directory")
 }
 
 func TestGoGetInsecure(t *testing.T) {

src/cmd/go/internal/load/pkg.go

@@ -544,9 +544,13 @@ func loadImport(pre *preload, path, srcDir string, parent *Package, stk *ImportS
 
 	if p.Internal.Local && parent != nil && !parent.Internal.Local {
 		perr := *p
+		errMsg := fmt.Sprintf("local import %q in non-local package", path)
+		if path == "." {
+			errMsg = "cannot import current directory"
+		}
 		perr.Error = &PackageError{
 			ImportStack: stk.Copy(),
-			Err:         fmt.Sprintf("local import %q in non-local package", path),
+			Err:         errMsg,
 		}
 		return setErrorPos(&perr, importPos)
 	}