Re: Question on tree-walking and mutually-recursive types

[kenner at vlsi1 dot ultra dot nyu dot edu (Richard Kenner)]

    Ignoring the fun algorithms bits downthread, I believe you'll find
    that most of the time we're interested in walking trees, we're *not*
    interested in walking the types.  I think you'll find that the 
    majority of the callbacks to walk_tree include

	if (TYPE_P (*tp))
	  *walk_subtrees = 0;

Yes.  Indeed I noticed that.

    I think that we should be able to characterize some major pieces of
    Then we say that it's an error to call walk_tree with flags that 
    allow types but not including a hash table, and enforce that with
    an abort.

Perhaps.  But this is indeed a large change to deal with something that
will never occur in real code and which we think is only permitted
in Ada and Algol 68.