ConcurrentWeakMap-related minor improvements (#3346)

Author: qwwdfsad

kotlinx-coroutines-core/jvm/src/debug/internal/ConcurrentWeakMap.kt

@@ -10,11 +10,10 @@ import java.lang.ref.*
 
 // This is very limited implementation, not suitable as a generic map replacement.
 // It has lock-free get and put with synchronized rehash for simplicity (and better CPU usage on contention)
-@OptIn(ExperimentalStdlibApi::class)
 @Suppress("UNCHECKED_CAST")
 internal class ConcurrentWeakMap<K : Any, V: Any>(
     /**
-     * Weak reference queue is needed when a small key is mapped to a large value and we need to promptly release a
+     * Weak reference queue is needed when a small key is mapped to a large value, and we need to promptly release a
      * reference to the value when the key was already disposed.
      */
     weakRefQueue: Boolean = false

kotlinx-coroutines-core/jvm/test/TestBase.kt

@@ -236,8 +236,9 @@ public actual open class TestBase(private var disableOutCheck: Boolean)  {
             if (expected != null) {
                 if (!expected(e))
                     error("Unexpected exception: $e", e)
-            } else
+            } else {
                 throw e
+            }
         } finally {
             if (ex == null && expected != null) error("Exception was expected but none produced")
         }

kotlinx-coroutines-core/jvm/test/internal/ConcurrentWeakMapOperationStressTest.kt

@@ -34,7 +34,7 @@ class ConcurrentWeakMapOperationStressTest : TestBase() {
                 var generationOffset = 0L
                 while (!stop.value) {
                     val kvs = (generationOffset + batchSize * index until generationOffset + batchSize * (index + 1))
-                        .associateBy({ Key(it) }, {  it * it })
+                        .associateBy({ Key(it) }, { it * it })
                     generationOffset += batchSize * nThreads
                     for ((k, v) in kvs) {
                         assertEquals(null, m.put(k, v))
@@ -45,8 +45,8 @@ class ConcurrentWeakMapOperationStressTest : TestBase() {
                     for ((k, v) in kvs) {
                         assertEquals(v, m.remove(k))
                     }
-                    for ((k, v) in kvs) {
-                        assertEquals(null, m.get(k))
+                    for ((k, _) in kvs) {
+                        assertEquals(null, m[k])
                     }
                     count.incrementAndGet()
                 }
@@ -68,6 +68,6 @@ class ConcurrentWeakMapOperationStressTest : TestBase() {
         }
         stop.value = true
         threads.forEach { it.join() }
-        assertEquals(0, m.size)
+        assertEquals(0, m.size, "Unexpected map state: $m")
     }
-}
+}