❓ What is garbage collected?

What is garbage collected or not ?

🐕	garbage collected?
integers	no because not allocated?
booleans	no because not allocated?
nil	no because not allocated?
strings	yes
symbols	it depends?
constants	If you remove a constant, the object it points to will be GC'd. But constants aren't really a type of object, it's just a name. source
freeze objects	yes
arrays	yes?
hashes	yes?
what else?	?