Remove returns unit markers in suspend lambdas

compiler/backend/src/org/jetbrains/kotlin/codegen/coroutines/CoroutineTransformerMethodVisitor.kt

@@ -94,6 +94,8 @@ class CoroutineTransformerMethodVisitor(
             continuationIndex = methodNode.maxLocals++
 
             prepareMethodNodePreludeForNamedFunction(methodNode)
+        } else {
+            ReturnUnitMethodTransformer.cleanUpReturnsUnitMarkers(methodNode, ReturnUnitMethodTransformer.findReturnsUnitMarks(methodNode))
         }
 
         for (suspensionPoint in suspensionPoints) {

compiler/backend/src/org/jetbrains/kotlin/codegen/coroutines/ReturnUnitMethodTransformer.kt

@@ -124,10 +124,10 @@ object ReturnUnitMethodTransformer : MethodTransformer() {
     private fun findReturnUnitSequences(methodNode: MethodNode): Collection<AbstractInsnNode> =
         methodNode.instructions.asSequence().filter { it.isUnitInstance() && it.next?.opcode == Opcodes.ARETURN }.toList()
 
-    private fun findReturnsUnitMarks(methodNode: MethodNode): Collection<AbstractInsnNode> =
+    internal fun findReturnsUnitMarks(methodNode: MethodNode): Collection<AbstractInsnNode> =
         methodNode.instructions.asSequence().filter(::isReturnsUnitMarker).toList()
 
-    private fun cleanUpReturnsUnitMarkers(methodNode: MethodNode, unitMarks: Collection<AbstractInsnNode>) {
+    internal fun cleanUpReturnsUnitMarkers(methodNode: MethodNode, unitMarks: Collection<AbstractInsnNode>) {
         unitMarks.forEach { methodNode.instructions.removeAll(listOf(it.previous, it)) }
     }
 }

compiler/testData/codegen/bytecodeText/coroutines/returnUnitInLambda.kt

@@ -0,0 +1,29 @@
+// WITH_RUNTIME
+// WITH_COROUTINES
+
+import helpers.*
+import kotlin.coroutines.experimental.*
+import kotlin.coroutines.experimental.intrinsics.*
+// TREAT_AS_ONE_FILE
+
+var res = "FAIL"
+
+suspend fun suspendHere() = suspendCoroutineOrReturn<Unit> {
+    res = "OK"
+    it.resume(Unit)
+    COROUTINE_SUSPENDED
+}
+
+fun builder(c: suspend () -> Unit) {
+    c.startCoroutine(EmptyContinuation)
+}
+
+fun box() : String {
+    builder {
+        suspendHere()
+    }
+    return res
+}
+
+// 0 ICONST_2
+// 0 ICONST_3

compiler/tests/org/jetbrains/kotlin/codegen/BytecodeTextTestGenerated.java

@@ -1137,6 +1137,12 @@ public class BytecodeTextTestGenerated extends AbstractBytecodeTextTest {
             doTest(fileName);
         }
 
+        @TestMetadata("returnUnitInLambda.kt")
+        public void testReturnUnitInLambda() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/bytecodeText/coroutines/returnUnitInLambda.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("varValueConflictsWithTable.kt")
         public void testVarValueConflictsWithTable() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/codegen/bytecodeText/coroutines/varValueConflictsWithTable.kt");