Resolve factoryBeanClass if necessary

Update `AbstractAutowireCapableBeanFactory.getTypeForFactoryBean` to
use fallback to `determineTargetType` if the factory bean definition
does not have a resolved class.

This is required for the case where a `@Configuration` class is picked
up via component scanning and has a bean type that has not yet been
resolved.

Closes spring-projectsgh-23338

Author: philwebb

spring-beans/src/main/java/org/springframework/beans/factory/support/AbstractAutowireCapableBeanFactory.java

@@ -858,9 +858,16 @@ protected ResolvableType getTypeForFactoryBean(String beanName,
 				// Try to obtain the FactoryBean's object type from its factory method
 				// declaration without instantiating the containing bean at all.
 				BeanDefinition factoryBeanDefinition = getBeanDefinition(factoryBeanName);
-				if (factoryBeanDefinition instanceof AbstractBeanDefinition &&
-						((AbstractBeanDefinition) factoryBeanDefinition).hasBeanClass()) {
-					Class<?> factoryBeanClass = ((AbstractBeanDefinition) factoryBeanDefinition).getBeanClass();
+				Class<?> factoryBeanClass = null;
+				if (factoryBeanDefinition instanceof AbstractBeanDefinition
+						&& ((AbstractBeanDefinition) factoryBeanDefinition).hasBeanClass()) {
+					factoryBeanClass = ((AbstractBeanDefinition) factoryBeanDefinition).getBeanClass();
+				}
+				else {
+					RootBeanDefinition fbmbd = getMergedBeanDefinition(factoryBeanName, factoryBeanDefinition);
+					factoryBeanClass = determineTargetType(factoryBeanName, fbmbd, new Class<?>[] { Object.class });
+				}
+				if (factoryBeanClass != null) {
 					result = getTypeForFactoryBeanFromMethod(factoryBeanClass, factoryMethodName);
 					if (result.resolve() != null) {
 						return result;