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is it a bug that `runBlocking(JavaFx) { runBlocking(JavaFx) { }}` causes deadlock but `runBlocking(JavaFx) { runBlocking { }}` does not?

I would create an issue on Kotlinx.coroutines issue tracker

in the second example you are creating a local event loop within a single event being processed on the `JavaFx` dispatcher and blocking the `JavaFx` thread until that new event loop exits, but in the first example the inner `runBlocking(JavaFx)` says, "block the current thread I am on until the coroutine I would like to run on the JavaFx dispatcher completes", but you're already on the JavaFx dispatcher and blocking it, so the thing you're waiting for can't start.

it would kind of violate the contract of `runBlocking` if there were some magic in there to turn it into a trampoline in cases like this

Seems to work as advertised. The docs explain both cases clearly: <https://kotlin.github.io/kotlinx.coroutines/kotlinx-coroutines-core/kotlinx.coroutines/run-blocking.html>

File an issue if you have a use-case where you want the other one not to block. 