How to check Kotlin BufferedReader use { return something } has called method close()? - kotlin

Question

My sample Kotlin about BufferedReader().use {}
I wonder if the close() is called when I return early in the use block
fun main() {
sendGet()
}
fun sendGet() {
val queryUrl = "http://www.google.com/search?q=kotlin&ie=utf-8&oe=utf-8"
val url = URL(queryUrl)
val conn = url.openConnection() as HttpURLConnection
conn.requestMethod = "GET"
conn.setRequestProperty("User-Agent", "Mozilla/5.0")
val responseCode = conn.responseCode
println("Response code: ${responseCode}")
when (responseCode) {
200 -> {
println("response: ${conn.getResponseText()}")
}
else -> println("Bad response code: ${responseCode}")
}
}
private fun HttpURLConnection.getResponseText(): String {
BufferedReader(InputStreamReader(inputStream)).use {
return it.readText()
}
}

Answer 1

You can see the source code for use in stdlib by navigating using "Go to implementation" (Cmd + B on a Mac):
public inline fun <T : Closeable?, R> T.use(block: (T) -> R): R {
var exception: Throwable? = null
try {
return block(this)
} catch (e: Throwable) {
exception = e
throw e
} finally {
when {
apiVersionIsAtLeast(1, 1, 0) -> this.closeFinally(exception)
this == null -> {}
exception == null -> close()
else ->
try {
close()
} catch (closeException: Throwable) {
// cause.addSuppressed(closeException) // ignored here
}
}
}
}
Because the call to close is inside the finally block, it will execute even on an early return.