ReadWrite.forEachLine with suspending action not compiling

Libraries
1

I have a BufferedReader that I want to use to perform a suspending action on reading each line.

fileReader.useLines { it.forEach { someSuspendFunction() } }

compiles, whereas the more succinct but nearly identical

fileReader.forEachLine { someSuspendFunction() }

does not compile. I get the error “Suspension functions can be called only within coroutine body”

I think it should be fine given that the definition of “forEachLine” is simply:

useLines { it.forEach(action) }

Am I missing some reason why this code should not compile? Or is there a bug where forEachLine should really be an inline function, or something?

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2

We decided that forEachLine should not be an inline function due to a large amount of bytecode it would have produced on the call site, be it inline.

3

Thanks, Ilya. Is that the reason that forEachLine cannot be used with suspending functions, then? Or was I missing something?

4

Yes, suspending inside a non-suspend lambda function is only possible in a lambda that is inlined into another suspend function.

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