关于IntelliJ IDEA误报“Useless expression”警告的技术问询

Let's break down what's going on here—you're absolutely right that this warning is incorrect, and your code logic is sound.

First, let's clarify the purpose of that attempt.get line:

• Your Try block wraps operations that might fail. If those operations throw an exception, Try catches it and stores it as a Failure instance.
• When you call attempt.get, if the result is a Failure, it re-throws the caught exception. If it's a Success, it returns the Unit result (which is why IDEA naively thinks it's "useless").

The issue here is IntelliJ's static analysis only looks at the return value of the expression, not its critical side effects. Since the expression returns Unit and you don't assign or pass that value anywhere, IDEA flags it as useless—but it misses the key behavior: throwing an exception if the operation failed.

If you removed that line entirely, any exceptions inside the Try block would be silently swallowed. Your method would run logout and return Unit as if nothing went wrong, which is almost certainly not what you want. The attempt.get ensures that failures bubble up to the caller, making errors visible instead of hiding them.

If you want to suppress the warning (or make IDEA's analysis happier), you have a few straightforward options:

• Add a comment to explicitly ignore the warning: //noinspection ScalaUselessExpression right above the line
• Rewrite it to make the side effect more explicit, like attempt.fold(throw _, _ => ())—this makes it clear you're handling both success and failure cases, and IDEA won't flag it
• Or just leave it as-is, since your logic is correct and this is just a tooling quirk

内容的提问来源于stack exchange，提问作者Alexander Arendar