I have a Coroutines extension leveraging some Java...

# coroutines

[sdeleuze]

I have a Coroutines extension leveraging some Java methods specified as suspend fun <T : Any> RowsFetchSpec<T>.awaitOne(): T = one().awaitSingle() but when it used, type inference shows T!, what did I miss? I have specified that T extends non nullable Any so I would expect return type T.

[sdeleuze]

message has been deleted

[diesieben07]

Since the T is inferred from the RowFetchSpec instance, which is the Java class, T automatically becomes a flexible type.

[sdeleuze]

Hum, I am pretty sure that I used <T : Any> for non suspending extensions to enforce return type non-nullability. And even when I use suspend fun <T> RowsFetchSpec<T>.awaitOne() = one().awaitSingle()!! the inferred type on usage side is still T! while it is shown as T on extension definition side.

[sdeleuze]

I am suspecting an issue related to Java interop + extensions + suspending functions.

[sdeleuze]

Otherwise, how can I define this extension to return a non nullable type? What could be more explicit than suspend fun <T> RowsFetchSpec<T>.awaitOne() = one().awaitSingle()!!?

[diesieben07]

Okay, putting it like that is a different thing. Maybe this is a bug, but now I'm in over my head 😄

[sdeleuze]

I have a simple repro, I will create an issue

[sdeleuze]

https://youtrack.jetbrains.com/issue/KT-30922