KTOR-2914 Change exception type and clarify message

ktor-network/jvm/src/io/ktor/network/selector/SelectorManagerSupport.kt

@@ -4,6 +4,7 @@
 
 package io.ktor.network.selector
 
+import io.ktor.utils.io.errors.*
 import kotlinx.coroutines.*
 import java.nio.channels.*
 import java.nio.channels.spi.*
@@ -33,15 +34,9 @@ public abstract class SelectorManagerSupport internal constructor() : SelectorMa
     public final override suspend fun select(selectable: Selectable, interest: SelectInterest) {
         val interestedOps = selectable.interestedOps
         val flag = interest.flag
-        if (interestedOps and flag == 0) {
-            val message = if (selectable.isClosed) {
-                "Selectable is closed"
-            } else {
-                "Selectable is invalid state: $interestedOps, $flag"
-            }
 
-            throw IllegalArgumentException(message)
-        }
+        if (selectable.isClosed) selectableIsClosed()
+        if (interestedOps and flag == 0) selectableIsInvalid(interestedOps, flag)
 
         suspendCancellableCoroutine<Unit> { continuation ->
             continuation.invokeOnCancellation {
@@ -179,3 +174,11 @@ public abstract class SelectorManagerSupport internal constructor() : SelectorMa
 
     public class ClosedSelectorCancellationException : CancellationException("Closed selector")
 }
+
+private fun selectableIsClosed(): Nothing {
+    throw IOException("Selectable is already closed")
+}
+
+private fun selectableIsInvalid(interestedOps: Int, flag: Int): Nothing {
+    error("Selectable is invalid state: $interestedOps, $flag")
+}

ktor-network/jvm/test/io/ktor/network/selector/ActorSelectorManagerTest.kt

@@ -0,0 +1,43 @@
+/*
+ * Copyright 2014-2022 JetBrains s.r.o and contributors. Use of this source code is governed by the Apache 2.0 license.
+ */
+
+package io.ktor.network.selector
+
+import io.mockk.*
+import kotlinx.coroutines.*
+import org.junit.*
+import org.junit.Test
+import java.io.*
+import kotlin.test.*
+
+class ActorSelectorManagerTest {
+    val manager = ActorSelectorManager(Dispatchers.Default)
+
+    @After
+    fun tearDown() {
+        manager.close()
+    }
+
+    @Test
+    fun testSelectableIsClosed(): Unit = runBlocking {
+        val selectable: Selectable = mockk()
+        every { selectable.interestedOps } returns SelectInterest.READ.flag
+        every { selectable.isClosed } returns true
+
+        assertFailsWith<IOException> {
+            manager.select(selectable, SelectInterest.READ)
+        }
+    }
+
+    @Test
+    fun testSelectOnWrongInterest(): Unit = runBlocking {
+        val selectable: Selectable = mockk()
+        every { selectable.interestedOps } returns SelectInterest.READ.flag
+        every { selectable.isClosed } returns false
+
+        assertFailsWith<IllegalStateException> {
+            manager.select(selectable, SelectInterest.WRITE)
+        }
+    }
+}