anchor.diff:    }
   
     /// Executes [callback] in a transaction, and returns the callback's return value.
  +  ///
     /// If the callbacks throws an exception, the transaction will be rolled back
     /// and the exception propagated, otherwise the transaction will be committed.
     transaction(callback()) {
  
positive.code:   }
  
    /// Executes a single SQL statement.
    /// See [Statement#execute].
    int execute(String statement, [params=const [], bool callback(Row)]) {
      _checkOpen();
      statement = prepare(statement);
  
negative.code: #import("dart-ext:dart_sqlite");
  
  /// A connection to a SQLite database. 
  ///
  /// Each database must be [close]d after use.
  class Database {
    var _db;
    /// The location on disk of the database file.
  