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