Support sealed class inheritors in the same file

#KT-11573 Fixed

compiler/testData/diagnostics/tests/sealed/DerivedTopLevel.kt

@@ -0,0 +1,10 @@
+sealed class Base
+
+class Derived: Base() {
+    class Derived2: <!INVISIBLE_MEMBER, SEALED_SUPERTYPE!>Base<!>()
+}
+
+fun test() {
+    class Local: <!INVISIBLE_MEMBER, SEALED_SUPERTYPE!>Base<!>()
+}
+

compiler/testData/diagnostics/tests/sealed/DerivedTopLevel.txt

@@ -1,5 +1,7 @@
 package
 
+public fun test(): kotlin.Unit
+
 public sealed class Base {
     private constructor Base()
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
@@ -12,4 +14,11 @@ public final class Derived : Base {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
     public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
     public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+    public final class Derived2 : Base {
+        public constructor Derived2()
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
 }

compiler/testData/diagnostics/tests/sealed/NeverDerived.kt

@@ -1,7 +0,0 @@
-sealed class Base {
-
-}
-
-class Derived: <!INVISIBLE_MEMBER, SEALED_SUPERTYPE!>Base<!>() {
-
-}

compiler/testData/diagnostics/tests/sealed/NeverDerivedFromNested.kt

@@ -0,0 +1,9 @@
+class A {
+    sealed class Base
+}
+
+class Derived : <!INVISIBLE_MEMBER, SEALED_SUPERTYPE!>A.Base<!>()
+
+fun test() {
+    class DerivedLocal : <!INVISIBLE_MEMBER, SEALED_SUPERTYPE!>A.Base<!>()
+}

compiler/testData/diagnostics/tests/sealed/NeverDerivedFromNested.txt

@@ -0,0 +1,24 @@
+package
+
+public fun test(): kotlin.Unit
+
+public final class A {
+    public constructor A()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+
+    public sealed class Base {
+        private constructor Base()
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+}
+
+public final class Derived : A.Base {
+    public constructor Derived()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}