IntelliJ/Kotlin: What does the `^use` hint mean?

Question

I'm using Kotlin in IntelliJ. I've written a fairly typical recursive function with a couple streams to zip up some files. I'm seeing a ^use and I don't know what IntelliJ is trying to tell me. (Hovering over such things usually teaches me something I didn't know about the language or warns me about a common mistake, but this provides no details)

Here is the screenshot of my function with an arrow pointing to the the hint.

Answer 1

This hint marks an expression that is a return value of a lambda, also saying which function the lambda is passed to. It reads as 'returned from the lambda passed to use { ... }'.

As the last expression in each lambda is the return value, this hint helps finding which lambda the expression is actually returned from.

You can disable these hints in the IDE preferences: Editor → General → Appearance → Show parameter hints – Configure → Language: Kotlin → Show lambda return expression hints (also available from the hint's right click menu), the other kinds of inline hints are also set up there.

UPD: In IntelliJ IDEA 2019.3 and newer, these options are placed under Editor → Inlay Hints → Kotlin.