unstable number of arguments to yylex

[John]

In a  %pure parser, the number of arguments to yylex() is dependent
upon whether any @N constructs are detected. This is a problem during
development when one removes or comments out certain actions that
contain @N constructs. Suddenly, the compiler may produce errors about
the number of arguments to yylex.

Is there a concrete method to force the number of parameters to be
stable -- either one or two, but not flip-flop between them?