George Yoshida points out that the special characters

from Tools/compiler/ast.txt are not used anywhere else in asttable.txt.
So remove "\&".

Doc/lib/asttable.tex

@@ -273,7 +273,7 @@
 \hline 
 
 \lineiii{With}{\member{expr}}{}
-\lineiii{}{\member{vars\&}}{}
+\lineiii{}{\member{vars}}{}
 \lineiii{}{\member{body}}{}
 \hline