anchor.diff:  ///     ThrowStatement
   ///     TryStatement
   ///     DebuggerStatement
  +///     TODO: remove import, export and lexical from statements
   statement
    : block
    | variableStatement
  
positive.code:  | debuggerStatement
   | importStatement
   | exportStatement
   ;
  
  importStatement
   : 'import' importClause fromClause ';'?
  
negative.code:   | 'export' namedImports fromClause? ';'?
    | 'export' variableStatement
    | 'export' functionDeclaration
    | 'export' lexicalStatement
    | 'export' 'default' functionDeclaration
    | 'export' 'default' singleExpression ';'?
  ;
  