Can not resolve symbol

Hello Sevilayceker,

Thank you for contacting Rider support.
Indeed, it is not obvious how to make ANTLR generator work.

Please find the following tips. Hope it helps:

• Install the ANTLR v4 plugin in Rider. Restart Rider;
• My path to .sln file is: /Users/Dmitrii.Kazantsev/Downloads/firstAntlr/firstAntlr.sln. 
  I made antlr sources to be generated in /Users/Dmitrii.Kazantsev/Downloads/firstAntlr/Gen/Tiny folder using the following config: 
  So, you would need to choose {PathToFolderParentToFolderWithSolution} as an Output directory; Also set the namespace for the generated code like firstAntlr.{DesiredFolder}.Tiny. Do not forget to set the CSharp as a language;
• When you configured these settings, open the .g4 file;
• Select Tools | Generate ANTLR Recognizer. It should generate sources under {SolutionFolder}.{DesiredFolder}.Tiny;
• Likely still there will be "Can't resolve symbol errors". I suggest deleting all the entries from the packages.config file and installing only necessary NuGet from the NuGet tool window. Delete entries from packages.config, save a file and open the NuGet tool window;
• Find the Antlr4.Runtime.Standard (It contains required symbols) NuGet and install it;
• If still there are errors, try restarting Rider;

Feel free to try out the solution I prepared based on yours. It builds and runs fine: https://uploads.jetbrains.com/files/2023_08_23_Bkq2bqyfs6ZiaTgkXnpcdZ_JBS/firstAntlr_working.zip?secret=9XmB5mCqJAnD31bJC7Ez7Gs428BAFfgh

If that doesn't help or you have any other questions or difficulties, please let me know.
Have a nice day!