internal/pkg: benchmark early DCE

This error has never had decent performance, now is a good time to improve that.

Signed-off-by: Ophestra <cat@gensokyo.uk>

internal/pkg/pkg_test.go

@@ -1603,6 +1603,24 @@ func (a earlyFailureF) Cure(*pkg.FContext) error {
 	return stub.UniqueError(0xcafe)
 }
 
+func BenchmarkEarlyDCE(b *testing.B) {
+	msg := message.New(log.New(os.Stderr, "dce: ", 0))
+	msg.SwapVerbose(testing.Verbose())
+	c, err := pkg.Open(b.Context(), msg, 0, 0, 0, check.MustAbs(b.TempDir()))
+	if err != nil {
+		b.Fatal(err)
+	}
+	_, _, err = c.Cure(earlyFailureF(8))
+	if !errors.Is(err, stub.UniqueError(0xcafe)) {
+		b.Fatalf("Cure: error = %v", err)
+	}
+	c.Close()
+
+	for b.Loop() {
+		err.Error()
+	}
+}
+
 func TestDependencyCureErrorEarly(t *testing.T) {
 	t.Parallel()