// %w accepts only errors.
	if m.t == argError {
		return types.ConvertibleTo(typ, errorType)
	}

	// If the type implements fmt.Formatter, we have nothing to check.
	if isFormatter(typ) {
		return true
	}

	// If we can use a string, might arg (dynamically) implement the Stringer or Error interface?
	if m.t&argString != 0 && isConvertibleToString(typ) {
		return true
	}