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