anchor.diff:  //Note that = is not really an assignment operator, but 
   //can be used to init locals
   expression 
  -    : methodExpression 
  +    : implicationExpression 
         ( ('=' | ':=' | '.=' | '+=' | '-=' | '*=' | '/=' | '%=' | '&=' | '|=' | '^=' | '&&=' | '||=' | '?=') assignable )?
  -    ;
  -
  -methodExpression
  -    : implicationExpression undelimitedNamedArgument*
  -    ;
  -
  -undelimitedNamedArgument
  -    : ( memberName | 'case' '(' expressions ')' ) 
  -      undelimitedNamedArgumentDefinition 
       ;
       
   implicationExpression
  
positive.code:         classBody
      ;
  
  classBody
      : '{' ((instanceStart)=>instances)? declarationOrStatement* '}'
      ;
  
negative.code:     | 'extension'
      ;
  
  statement 
      : expressionStatement
  //    | eventListener
  