I don't get it, why shouldn't it be cached?

ClassReflection created via withTypes has properties like isDeprecated, isGeneric, isInternal set to null

while the one created via getClass contains more information:

so by caching the withTypes created one, we have less information at hand later on when we respond to a getClassReflection() call with a cached object

Hmm no. This doesn't make sense. Will have another look tomorrow

had another look but still I am not yet sure about the causation.

the difference between caching and not caching is, that

• when caching generics ClassReflection for SplObjectStorage the template-type map will be ErrorType, ErrorType which causes lots of if instanceof ErrorType logic to happen and fallbacks are getting evaluated
• when not caching generics ClassReflection for SplObjectStorage the template-type map will reflect the unresolved types of the phpdoc stub