Adjust Gradle configuration to gradually introduce warnings as errors in a safe manner

* Also, add tests that verify our disabled assertions
* Fix nullability in AgentPremain that used to work by accident (because we disabled those assertions)

Author: qwwdfsad

build.gradle

@@ -168,18 +168,7 @@ configure(subprojects.findAll { !sourceless.contains(it.name) && it.name != core
 apply plugin: "bom-conventions"
 
 // Configure subprojects with Kotlin sources
-configure(subprojects.findAll { !sourceless.contains(it.name) }) {
-    // Use atomicfu plugin, it also adds all the necessary dependencies
-    apply plugin: 'kotlinx-atomicfu'
-
-    // Configure options for all Kotlin compilation tasks
-    tasks.withType(AbstractKotlinCompile).all {
-        kotlinOptions.freeCompilerArgs += OptInPreset.optInAnnotations.collect { "-Xopt-in=" + it }
-        kotlinOptions.freeCompilerArgs += "-progressive"
-        // Remove null assertions to get smaller bytecode on Android
-        kotlinOptions.freeCompilerArgs += ["-Xno-param-assertions", "-Xno-receiver-assertions", "-Xno-call-assertions"]
-    }
-}
+apply plugin: "configure-compilation-conventions"
 
 if (build_snapshot_train) {
     println "Hacking test tasks, removing stress and flaky tests"

buildSrc/src/main/kotlin/configure-compilation-conventions.gradle.kts

@@ -0,0 +1,20 @@
+/*
+ * Copyright 2016-2022 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
+ */
+
+import org.jetbrains.kotlin.gradle.tasks.*
+
+configure(subprojects) {
+    if (name in sourceless) return@configure
+    apply(plugin = "kotlinx-atomicfu")
+    tasks.withType(KotlinCompile::class).all {
+        kotlinOptions {
+            val newOptions =
+                listOf(
+                    "-progressive", "-Xno-param-assertions", "-Xno-receiver-assertions",
+                    "-Xno-call-assertions"
+                ) + optInAnnotations.map { "-Xopt-in=$it" }
+            freeCompilerArgs = freeCompilerArgs + newOptions
+        }
+    }
+}

kotlinx-coroutines-core/jvm/src/debug/AgentPremain.kt

@@ -36,13 +36,13 @@ internal object AgentPremain {
 
     internal object DebugProbesTransformer : ClassFileTransformer {
         override fun transform(
-            loader: ClassLoader,
+            loader: ClassLoader?,
             className: String,
             classBeingRedefined: Class<*>?,
             protectionDomain: ProtectionDomain,
             classfileBuffer: ByteArray?
         ): ByteArray? {
-            if (className != "kotlin/coroutines/jvm/internal/DebugProbesKt") {
+            if (loader == null || className != "kotlin/coroutines/jvm/internal/DebugProbesKt") {
                return null
             }
             /*

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

@@ -0,0 +1,29 @@
+/*
+ * Copyright 2016-2022 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
+ */
+package kotlinx.coroutines
+
+import kotlinx.coroutines.*
+import org.junit.Test
+import kotlin.test.*
+
+
+class NoParamAssertionsTest : TestBase() {
+    // These tests verify that we haven't omitted "-Xno-param-assertions" and "-Xno-receiver-assertions"
+
+    @Test
+    fun testNoReceiverAssertion() {
+        val function: (ThreadLocal<Int>, Int) -> ThreadContextElement<Int> = ThreadLocal<Int>::asContextElement
+        @Suppress("UNCHECKED_CAST")
+        val unsafeCasted = function as ((ThreadLocal<Int>?, Int) -> ThreadContextElement<Int>)
+        unsafeCasted(null, 42)
+    }
+
+    @Test
+    fun testNoParamAssertion() {
+        val function: (ThreadLocal<Any>, Any) -> ThreadContextElement<Any> = ThreadLocal<Any>::asContextElement
+        @Suppress("UNCHECKED_CAST")
+        val unsafeCasted = function as ((ThreadLocal<Any?>?, Any?) -> ThreadContextElement<Any>)
+        unsafeCasted(ThreadLocal.withInitial { Any() }, null)
+    }
+}