[antlr-interest] Q: Why do pointers to types need a tree?

[Austin Hastings]

Ter,

In your http://antlr.org/wiki/display/CS652/Simple+scopes+solution 
document, you comment at one point that:

Symbol objects just map a name to a type (variable) or return type 
(function). (I've hinted at what you need for pointers to types; turns 
out to be a tree also).

Can you explain that last comment? While my implementation is an upside 
down tree, it's directional. So it qualifies as a DAG, but not as a 
tree. Why would I need a tree?

=Austin