anchor.diff:      ;
   
   assertStatement
  -    :    assertClause ';'
  -    ;
  -
  -assertClause
  +    :    assertion ';'
  +    ;
  +
  +assertion
       :    ASSERT '(' expression (',' expression)? ','? ')'
       ;
   
  
positive.code: 
  element
      : expressionElement
      | mapEntry
      | spreadElement
      | ifElement
      | forElement
  
negative.code: 
  metadatum
      :    constructorDesignation arguments
      |    qualifiedName
      ;
  
  expression
      :    functionExpression
      |    throwExpression
      |    assignableExpression assignmentOperator expression
      |    conditionalExpression
      |    cascade
      ;
  
  expressionWithoutCascade
  