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@lexer::members {
    class SaveStruct {
      SaveStruct(CharStream input){
        this.input = input;
        this.marker = input.mark();
      }
      public CharStream input;
      public int marker;
     }

     Stack<SaveStruct> includes = new Stack<SaveStruct>();

    // We should override this method for handling EOF of included file
     public Token nextToken(){
       Token token = super.nextToken();

       if(token.getType() == Token.EOF_TOKEN && !includes.empty()){
        // We've got EOF and have non empty stack.
         SaveStruct ss = includes.pop();
         setCharStream(ss.input);
         input.rewind(ss.marker);
         //this should be used instead of super [like below] to handle exits from nested includes
         //it matters, when the 'include' token is the last in previous stream (using super, lexer 'crashes' returning EOF token)
         token = this.nextToken();
       }

      // Skip first token after switching on another input.
      // You need to use this rather than super as there may be nested include files
       if(((CommonToken)token).getStartIndex() < 0)
         token = this.nextToken();

       return token;
     }
 }

// and lexer rule
 INCLUDE
     : 'include' (WS)? f=STRING {
       String name = f.getText();
       name = name.substring(1,name.length()-1);
       try {
        // save current lexer's state
         SaveStruct ss = new SaveStruct(input);
         includes.push(ss);

        // switch on new input stream
         setCharStream(new ANTLRFileStream(name));
         reset();

       } catch(Exception fnf) { throw new Error("Cannot open file " + name); }
     }
     ;