Fix #3476 (#3526)

backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/lower/NativeSuspendFunctionLowering.kt

@@ -338,11 +338,12 @@ internal class NativeSuspendFunctionsLowering(ctx: Context): AbstractSuspendFunc
                         suspendCall = newChildren[2]
                     }
                     expression.isSuspendCall -> {
-                        val lastChild = newChildren.last()
-                        if (lastChild != null) {
+                        val lastChildIndex = newChildren.indexOfLast { it != null }
+                        if (lastChildIndex != -1) {
                             // Save state as late as possible.
+                            val lastChild = newChildren[lastChildIndex]!!
                             calledSaveState = true
-                            newChildren[numberOfChildren - 1] =
+                            newChildren[lastChildIndex] =
                                     irBlock(lastChild) {
                                         if (lastChild.isPure()) {
                                             +irCall(saveState)

backend.native/tests/build.gradle

@@ -1622,6 +1622,10 @@ task coroutines_correctOrder1(type: KonanLocalTest) {
     source = "codegen/coroutines/correctOrder1.kt"
 }
 
+task coroutines_controlFlow_chain(type: KonanLocalTest) {
+    source = "codegen/coroutines/controlFlow_chain.kt"
+}
+
 task coroutines_controlFlow_if1(type: KonanLocalTest) {
     goldValue = "f1\ns1\nf3\n84\n"
     source = "codegen/coroutines/controlFlow_if1.kt"

backend.native/tests/codegen/coroutines/controlFlow_chain.kt

@@ -0,0 +1,43 @@
+/*
+ * Copyright 2010-2019 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license
+ * that can be found in the LICENSE file.
+ */
+
+package codegen.coroutines.controlFlow_chain
+
+import kotlin.test.*
+
+import kotlin.coroutines.*
+import kotlin.coroutines.intrinsics.*
+
+open class EmptyContinuation(override val context: CoroutineContext = EmptyCoroutineContext) : Continuation<Any?> {
+    companion object : EmptyContinuation()
+    override fun resumeWith(result: Result<Any?>) { result.getOrThrow() }
+}
+
+suspend fun suspendHere(): Int = suspendCoroutineUninterceptedOrReturn { x ->
+    x.resume(42)
+    COROUTINE_SUSPENDED
+}
+
+fun builder(c: suspend () -> Unit) {
+    c.startCoroutine(EmptyContinuation)
+}
+
+// See https://github.com/JetBrains/kotlin-native/issues/3476
+@Test fun runTest() {
+    var result = 0
+    builder {
+        foo().bar()
+        result = 1
+    }
+    assertEquals(1, result)
+}
+
+class Foo {
+    suspend fun bar() {
+        suspendHere()
+    }
+}
+
+suspend fun foo() = Foo()