code: protected Block visitBlock(Block block) {
          if (block == null) {
              return null;
          }
  
          Statement stmt = (Statement)block.accept(this);
  
          if (stmt instanceof Block) {
              return (Block)stmt;
          }
          else if (stmt != null) {
              return new Block(stmt);
          }
          else {
              return new Block(block.getSourceInfo());
          }
      }
docs: Visit a Block to ensure that new Statement is a Block.