// placeholders, so we won't sanity check input here and instead let the
	// driver deal with errors.
	want := -1

	var si driver.Stmt
	var cc ccChecker
	if ds != nil {
		si = ds.si
		want = ds.si.NumInput()
		cc.want = want
	}

	// Check all types of interfaces from the start.
	// Drivers may opt to use the NamedValueChecker for special
	// argument types, then return driver.ErrSkip to pass it along