springboot在prepareEnvironment函数中环境转换的问题

我在看springboot的源码，不太懂prepareEnvironment函数中为什么要有这个if代码块。

if的条件中是判断是否为自定义环境，如果是自定义环境那么就不会执行if代码块，如果是通过getOrCreateEnvironment创建的环境，说明不是自定义环境，那会进入if代码块执行。

进入if代码块后，会对环境进行转换，看convertEnvironmentfINecessary函数，最开始的类型判断应该一定会返回true的呀，在其他地方也没发现谁调用过convertEnvironmentIfNecessary这个函数，说明convertEnvironmentIfNecessary函数中的第二个return不会被执行。

那这么写的作用是什么，感谢各位大佬指导下。

        private ConfigurableEnvironment prepareEnvironment(SpringApplicationRunListeners listeners,

			DefaultBootstrapContext bootstrapContext, ApplicationArguments applicationArguments) {

		ConfigurableEnvironment environment = getOrCreateEnvironment();

		configureEnvironment(environment, applicationArguments.getSourceArgs());

		ConfigurationPropertySources.attach(environment);

		listeners.environmentPrepared(bootstrapContext, environment);

		DefaultPropertiesPropertySource.moveToEnd(environment);

		configureAdditionalProfiles(environment);

		bindToSpringApplication(environment);

		if (!this.isCustomEnvironment) {

			environment = new EnvironmentConverter(getClassLoader()).convertEnvironmentIfNecessary(environment,

					deduceEnvironmentClass());

		}

		ConfigurationPropertySources.attach(environment);

		return environment;

	}



       StandardEnvironment convertEnvironmentIfNecessary(ConfigurableEnvironment environment,

			Class<? extends StandardEnvironment> type) {

		if (type.equals(environment.getClass())) {

			return (StandardEnvironment) environment;

		}

		return convertEnvironment(environment, type);

	}



        private ConfigurableEnvironment getOrCreateEnvironment() {

		if (this.environment != null) {

			return this.environment;

		}

		switch (this.webApplicationType) {

		case SERVLET:

			return new StandardServletEnvironment();

		case REACTIVE:

			return new StandardReactiveWebEnvironment();

		default:

			return new StandardEnvironment();

		}

	}



     private Class<? extends StandardEnvironment> deduceEnvironmentClass() {

		switch (this.webApplicationType) {

		case SERVLET:

			return StandardServletEnvironment.class;

		case REACTIVE:

			return StandardReactiveWebEnvironment.class;

		default:

			return StandardEnvironment.class;

		}

	}