anchor.diff:     ;
   
   decl
  -   : idn (',' idn)* type_spec
  +   : idn (',' idn)* ':' type_spec
      ;
   
   returnz
  
positive.code:    ;
  
  cluster
     : idn '=' 'cluster' parms? 'is' idn (',' idn) where? cluster_body 'end' idn
     ;
  
  parms
     : param (',' param)*
     ;
  
  param
     : idn (',' idn)* ('type' | type_spec)
     ;
  
  args
  
negative.code:    ;
  
  signals
     : 'signals' '(' exception (',' exception)* ')'
     ;
  
  exception
  