Remove redundant continuation classes and INNERCLASS nodes

#KT-31339 Fixed

compiler/backend/src/org/jetbrains/kotlin/codegen/inline/AnonymousObjectTransformer.kt

@@ -141,7 +141,7 @@ class AnonymousObjectTransformer(
             superClassName,
             allCapturedParamBuilder.listCaptured()
         )
-        loop@for (next in methodsToTransform) {
+        loop@ for (next in methodsToTransform) {
             val deferringVisitor =
                 when {
                     coroutineTransformer.shouldSkip(next) -> continue@loop
@@ -162,9 +162,15 @@ class AnonymousObjectTransformer(
         }
 
         deferringMethods.forEach { method ->
+            val continuationToRemove = CoroutineTransformer.findFakeContinuationConstructorClassName(method.intermediate)
+            val oldContinuationName = coroutineTransformer.oldContinuationFrom(method.intermediate)
             coroutineTransformer.replaceFakesWithReals(method.intermediate)
             removeFinallyMarkers(method.intermediate)
             method.visitEnd()
+            if (continuationToRemove != null && coroutineTransformer.safeToRemoveContinuationClass(method.intermediate)) {
+                transformationResult.addClassToRemove(continuationToRemove)
+                innerClassNodes.removeIf { it.name == oldContinuationName }
+            }
         }
 
         SourceMapper.flushToClassBuilder(sourceMapper, classBuilder)

compiler/backend/src/org/jetbrains/kotlin/codegen/inline/coroutines/CoroutineTransformer.kt

@@ -215,6 +215,13 @@ class CoroutineTransformer(
     fun unregisterClassBuilder(continuationClassName: String) =
         (inliningContext as RegeneratedClassContext).continuationBuilders.remove(continuationClassName)
 
+    // If tail-call optimization took place, we do not need continuation class anymore, unless it is used by $$forInline method
+    fun safeToRemoveContinuationClass(method: MethodNode): Boolean = !generateForInline && !isStateMachine(method)
+
+    fun oldContinuationFrom(method: MethodNode): String? =
+        methods.find { it.name == method.name + FOR_INLINE_SUFFIX && it.desc == method.desc }
+                ?.let { findFakeContinuationConstructorClassName(it) }
+
     companion object {
         fun findFakeContinuationConstructorClassName(node: MethodNode): String? {
             val marker = node.instructions.asSequence().firstOrNull(::isBeforeFakeContinuationConstructorCallMarker) ?: return null