private TypeMirror getTypeMirror() {
            String methodName = getMethodName();
            if (methodName.startsWith("get") || methodName.startsWith("is")) {
                List<? extends VariableElement> params = element.getParameters();
                if (params.isEmpty()) {
                    return element.getReturnType();
                }
            } else if (methodName.startsWith("set")) {
                List<? extends VariableElement> params = element.getParameters();
                if (params.size() == 1) {
                    VariableElement param = params.iterator().next();
                    return param.asType();
                }
            }
            throw new IllegalStateException();
        }