anchor.diff:  
   // A line of user input in the interactive interpreter
   interpretable
  -  :	(importDeclaration 
  +  :	(importDeclaration
        | classDeclaration
        | statement)+
   	;
  
positive.code: grammar Noop;
  
  options {
  
negative.code: expression
  	: primary ('='^ expression)?
  	;
  
  primary
  	:	'('! expression ')'!
  	| (VariableIdentifier|TypeIdentifier|literal) ('.'^ (VariableIdentifier|TypeIdentifier) arguments?)*
  	;
  
  arguments
  	:	'(' expressionList? ')'
  	-> ^(ARGS expressionList?)
  