can not match on amb nodes in Tree

[BertLisser]

Created 2010-01-11 by [email protected] assigned to [email protected]

Due to the implementation of concrete syntax, I can't match amb nodes. There are several reasons, one is that the interpreter thinks I still have an ambiguity in my concrete syntax pattern (oops), the others are more difficult (places in the interpreter (deep matching) that assume that all Tree's are concrete syntax patterns.