"Implicitly discarding information" is just outright wrong.

All calls can have side effects, even calls that return a value. And while C# did recently add the discard operator _ to throw away returned values out of an e.g. Tuple, if you did as this critique suggests and flag every "discarded information" the language would become verbose/obnoxious.

For example:

      try 
      {   
            [....]
            myFirstDatabaseTransaction.Commit(); // Compiler warning: "Discarded Information" (it returns the transaction ID, but has the side effect of committing your changes to the database).   
      } 
      catch([...])
      { [...] }

Basic programmer errors are easily caught during development, because they're immediately wrong. Unlike null reference exceptions which sometimes can only be found after extensive usage of the system (due to different states, or underlying data changing).