I believe that the message is really a bit out of date, as it can be generated by my more than one kind of issue. From Java 7 there was a new category for Xlint, rawtypes, and raw type issues generate exactly the same warning. However, -Xlint:unchecked since Java 7 only reports on unchecked type conversions. If your issue is actually that you used a raw type, recompiling with Xlint:unchecked will not tell you where you did that.
An example is where you use a raw return type from a method. In this case you require -Xlint:rawtypes, or I would use Xlint:rawtypes,unchecked, since we don't know what kind of code actually caused that message.
I would not suppress the message as I want students to recognise the code smell. It is however a warning, rather than an error, and it is somewhat confusing that Coderunner presents it like a compilation error.
ChatGPT says this compiler message is "wrong -- but stable wrong".
An example is where you use a raw return type from a method. In this case you require -Xlint:rawtypes, or I would use Xlint:rawtypes,unchecked, since we don't know what kind of code actually caused that message.
I would not suppress the message as I want students to recognise the code smell. It is however a warning, rather than an error, and it is somewhat confusing that Coderunner presents it like a compilation error.
ChatGPT says this compiler message is "wrong -- but stable wrong".
Possibly (I've not tried it) you could also pass -Xlint:none if you want to suppress all the linter warnings.