Dont show warning for KT-21515 with LV>=1.3

compiler/frontend/src/org/jetbrains/kotlin/resolve/lazy/descriptors/LazyClassDescriptor.java

@@ -652,6 +652,12 @@ public class LazyClassDescriptor extends ClassDescriptorBase implements ClassDes
             }
         }
 
+        @Override
+        protected boolean getShouldReportCyclicScopeWithCompanionWarning() {
+            return !c.getLanguageVersionSettings()
+                    .supportsFeature(LanguageFeature.ProhibitVisibilityOfNestedClassifiersFromSupertypesOfCompanion);
+        }
+
         @Override
         protected void reportScopesLoopError(@NotNull KotlinType type) {
             PsiElement reportOn = DescriptorToSourceUtils.getSourceFromDescriptor(type.getConstructor().getDeclarationDescriptor());

compiler/testData/diagnostics/tests/cyclicHierarchy/withCompanion/everythingInOneScope_after.kt

@@ -2,14 +2,14 @@
 // see https://youtrack.jetbrains.com/issue/KT-21515
 
 open class Container {
-    open class <!CYCLIC_SCOPES_WITH_COMPANION!>Base<!> {
+    open class Base {
         open fun m() {}
     }
 
     // note that Base() supertype will be resolved in scope that was created on recursion
-    abstract class <!CYCLIC_SCOPES_WITH_COMPANION!>DerivedAbstract<!> : Base()
+    abstract class DerivedAbstract : Base()
 
-    companion <!CYCLIC_SCOPES_WITH_COMPANION!>object<!> : DerivedAbstract() {
+    companion object : DerivedAbstract() {
         override fun m() {}
     }
 }

compiler/testData/diagnostics/tests/cyclicHierarchy/withCompanion/noMembers_after.kt

@@ -1,15 +1,15 @@
 // !LANGUAGE: +ProhibitVisibilityOfNestedClassifiersFromSupertypesOfCompanion
 // see https://youtrack.jetbrains.com/issue/KT-21515
 
-abstract class <!CYCLIC_SCOPES_WITH_COMPANION!>DerivedAbstract<!> : C.Base() {
+abstract class DerivedAbstract : C.Base() {
     open class Data
 }
 
 public class C {
 
-    open class <!CYCLIC_SCOPES_WITH_COMPANION!>Base<!> ()
+    open class Base ()
 
     class Foo : <!UNRESOLVED_REFERENCE!>Data<!>()
 
-    companion <!CYCLIC_SCOPES_WITH_COMPANION!>object<!> : DerivedAbstract()
+    companion object : DerivedAbstract()
 }

compiler/testData/diagnostics/tests/cyclicHierarchy/withCompanion/onlyInterfaces_after.kt

@@ -6,13 +6,13 @@ open class Container {
     // (this is case because we can't know if there are any loops without resolving, but resolving
     // itself provokes loops)
 
-    interface <!CYCLIC_SCOPES_WITH_COMPANION!>Base<!> {
+    interface Base {
         open fun m() {}
     }
 
-    interface <!CYCLIC_SCOPES_WITH_COMPANION!>DerivedAbstract<!> : Base
+    interface DerivedAbstract : Base
 
-    companion <!CYCLIC_SCOPES_WITH_COMPANION!>object<!> : DerivedAbstract {
+    companion object : DerivedAbstract {
         override fun m() {}
     }
 }

compiler/testData/diagnostics/tests/cyclicHierarchy/withCompanion/typeIsLowEnough.kt

@@ -1,20 +1,20 @@
 // see https://youtrack.jetbrains.com/issue/KT-21515
 
-abstract class <!CYCLIC_SCOPES_WITH_COMPANION!>DerivedAbstract<!> : C.Base() {
+abstract class DerivedAbstract : C.Base() {
     override abstract fun m()
 }
 
 public class C {
     class Data
 
-    open class <!CYCLIC_SCOPES_WITH_COMPANION!>Base<!> () {
+    open class Base () {
         open fun m() {}
     }
 
     // Note that Data is resolved successfully here because we don't step on error-scope
     val data: Data = Data()
 
-    companion <!CYCLIC_SCOPES_WITH_COMPANION!>object<!> : DerivedAbstract() {
+    companion object : DerivedAbstract() {
         override fun m() {}
     }
 }

compiler/testData/diagnostics/tests/cyclicHierarchy/withCompanion/withIrrelevantInterface_after.kt

@@ -4,7 +4,7 @@
 interface SomeIrrelevantInterface
 
 // note that C.Base() supertype will be resolved in normal scope
-abstract class <!CYCLIC_SCOPES_WITH_COMPANION!>DerivedAbstract<!> : C.Base()
+abstract class DerivedAbstract : C.Base()
 
 class Data
 
@@ -14,7 +14,7 @@ public class C {
 
     // Note that any supertype of Base will be resolved in error-scope, even if it absolutely irrelevant
     // to the types in cycle.
-    open class <!CYCLIC_SCOPES_WITH_COMPANION!>Base<!>() : SomeIrrelevantInterface
+    open class Base() : SomeIrrelevantInterface
 
-    companion <!CYCLIC_SCOPES_WITH_COMPANION!>object<!> : DerivedAbstract()
+    companion object : DerivedAbstract()
 }

compiler/testData/diagnostics/tests/cyclicHierarchy/withCompanion/withMembers_after.kt

@@ -2,37 +2,37 @@
 // see https://youtrack.jetbrains.com/issue/KT-21515
 
 object WithFunctionInBase {
-    abstract class <!CYCLIC_SCOPES_WITH_COMPANION!>DerivedAbstract<!> : C.Base()
+    abstract class DerivedAbstract : C.Base()
 
     class Data
 
     public class C {
         val data: Data = Data()
 
-        open class <!CYCLIC_SCOPES_WITH_COMPANION!>Base<!>() {
+        open class Base() {
             fun foo(): Int = 42
         }
 
-        companion <!CYCLIC_SCOPES_WITH_COMPANION!>object<!> : DerivedAbstract()
+        companion object : DerivedAbstract()
     }
 }
 
 object WithPropertyInBase {
     // This case is very similar to previous one, but there are subtle differences from POV of implementation
 
-    abstract class <!CYCLIC_SCOPES_WITH_COMPANION!>DerivedAbstract<!> : C.Base()
+    abstract class DerivedAbstract : C.Base()
 
     class Data
 
     public class C {
 
-        open class <!CYCLIC_SCOPES_WITH_COMPANION!>Base<!>() {
+        open class Base() {
             val foo: Int = 42
         }
 
         val data: Data = Data()
 
-        companion <!CYCLIC_SCOPES_WITH_COMPANION!>object<!> : DerivedAbstract()
+        companion object : DerivedAbstract()
     }
 }
 
@@ -41,18 +41,18 @@ object WithPropertyInBaseDifferentOrder {
     // Note how position of property in file affected order of resolve, and, consequently, its results and
     // diagnostics.
 
-    abstract class <!CYCLIC_SCOPES_WITH_COMPANION!>DerivedAbstract<!> : C.Base()
+    abstract class DerivedAbstract : C.Base()
 
     class Data
 
     public class C {
         val data: Data = Data()
 
-        open class <!CYCLIC_SCOPES_WITH_COMPANION!>Base<!>() {
+        open class Base() {
             val foo: Int = 42
 
         }
 
-        companion <!CYCLIC_SCOPES_WITH_COMPANION!>object<!> : DerivedAbstract()
+        companion object : DerivedAbstract()
     }
 }

compiler/testData/diagnostics/tests/cyclicHierarchy/withCompanion/withoutTypeReference.kt

@@ -1,17 +1,17 @@
 // see https://youtrack.jetbrains.com/issue/KT-21515
 
-abstract class <!CYCLIC_SCOPES_WITH_COMPANION!>DerivedAbstract<!> : C.Base()
+abstract class DerivedAbstract : C.Base()
 
 class Data
 
 open class C {
-    open class <!CYCLIC_SCOPES_WITH_COMPANION!>Base<!> {
+    open class Base {
         open fun m() {}
     }
 
     val field = Data()
 
-    companion <!CYCLIC_SCOPES_WITH_COMPANION!>object<!> : DerivedAbstract() {
+    companion object : DerivedAbstract() {
         override fun m() {}
     }
 }

core/descriptors/src/org/jetbrains/kotlin/types/AbstractTypeConstructor.kt

@@ -97,11 +97,13 @@ abstract class AbstractTypeConstructor(storageManager: StorageManager) : TypeCon
             // We also check if there are a loop with additional edges going from owner of companion to
             // the companion itself.
             // Note that we use already disconnected types to not report two diagnostics on cyclic supertypes
-            supertypeLoopChecker.findLoopsInSupertypesAndDisconnect(
-                this, resultWithoutCycles,
-                { it.computeNeighbours(useCompanions = true) },
-                { reportScopesLoopError(it) }
-            )
+            if (shouldReportCyclicScopeWithCompanionWarning) {
+                supertypeLoopChecker.findLoopsInSupertypesAndDisconnect(
+                    this, resultWithoutCycles,
+                    { it.computeNeighbours(useCompanions = true) },
+                    { reportScopesLoopError(it) }
+                )
+            }
 
             supertypes.supertypesWithoutCycles = (resultWithoutCycles as? List<KotlinType>) ?: resultWithoutCycles.toList()
         })
@@ -118,6 +120,7 @@ abstract class AbstractTypeConstructor(storageManager: StorageManager) : TypeCon
 
     // TODO: overload in AbstractTypeParameterDescriptor?
     protected open fun reportScopesLoopError(type: KotlinType) {}
+    protected open val shouldReportCyclicScopeWithCompanionWarning: Boolean = false
 
     protected open fun getAdditionalNeighboursInSupertypeGraph(useCompanions: Boolean): Collection<KotlinType> = emptyList()
     protected open fun defaultSupertypeIfEmpty(): KotlinType? = null