Return from `buildSequence` in Kotlin - kotlin

Question

I'm using the buildSequence function in Kotlin. How do I end the iteration in the middle of the function? I'm looking for something similar to C#'s yield break statement.
My code looks something like the following. I'm stuck at the TODO.
fun foo(list:List<Number>): Sequence<Number> = buildSequence {
if (someCondition) {
// TODO: Bail out early with an empty sequence
// return doesn't seem to work....
}
list.forEach {
yield(someProcessing(it))
}
}
EDIT
Apparently, I misdiagnosed the source. The issue is not returning from the buildSequence function. The following works for me:
fun foo(list:List<Number>): Sequence<Number> = buildSequence {
return#buildSequence
list.forEach {
yield(someProcessing(it))
}
}
EDIT 2
The issue is that I put the return in a local helper function that validates data at multiple points in the buildSequence (Hence the helper function). Apparently I'm not able to return from buildSequence within the helper function. The error message was not terribly helpful...

Answer 1

Just use return#buildSequence, which is a labeled return from lambda, while an unlabeled return would mean 'return from the function foo'.
See also: Whats does “return#” mean?

Answer 2

Since Kotlin v 1.3.x preferred sequence syntax changed. (buildSequence is replaced by kotlin.sequences.sequence)
Updated "early return from generator" code snippet (includes try-catch and == null early return examples) for post 1.3.x Kotlin:
// gen# is just a subjective name i gave to the code block.
// could be `anything#` you want
// Use of named returns prevents "'return' is not allowed here" errors.
private fun getItems() = sequence<Item> gen# {
val cursor: Cursor?
try {
cursor = contentResolver.query(uri,*args)
} catch (e: SecurityException) {
Log.w(APP_NAME, "Permission is not granted.")
return#gen
}
if (cursor == null) {
Log.w(APP_NAME, "Query returned nothing.")
return#gen
}
// `.use` auto-closes Closeable. recommend.
// https://kotlinlang.org/api/latest/jvm/stdlib/kotlin.io/use.html
cursor.use {
// iterate over cursor to step through the yielded records
while (cursor.moveToNext()) {
yield(Item.Factory.fromCursor(cursor))
}
}
}
(Thx for all the prior posts that helped me get on "named return" track.)