anchor.diff:      :   'retry'
       ;
   
  -VOID
  +VOID_MODIFIER
       :   'void'
       ;
   
  
positive.code: 
  formalParameterType
      : type ( '...' -> ^(SEQUENCED_TYPE type) | -> type )
      | VOID -> VOID
      ;
  
  // Control structures.
  
negative.code:     ;
  
  voidMethodArgument
      : VOID_MODIFIER parameterName formalParameters+ block
      -> parameterName ^(METHOD_ARGUMENT VOID_MODIFIER parameterName formalParameters+ block)
      ;
  
  typedMethodOrGetterArgument
  