[FE] Support sealed classes and interfaces from java

KT-43551
KT-41215

compiler/testData/diagnostics/testsWithJava15/sealedClasses/javaSealedInterfaceExhaustiveness.kt

@@ -0,0 +1,64 @@
+// !DIAGNOSTICS: -UNUSED_VARIABLE
+// ISSUE: KT-41215, KT-43551
+
+// FILE: Base.java
+public sealed interface Base permits A, B, E {}
+
+// FILE: A.java
+public non-sealed interface A extends Base {}
+
+// FILE: B.java
+public sealed interface B extends Base permits B.C, B.D {
+    public static final class C implements B {}
+
+    public static non-sealed interface D extends B {}
+}
+
+// FILE: E.java
+public enum E implements Base {
+    First, Second
+}
+
+// FILE: main.kt
+fun test_ok_1(base: Base) {
+    val x = when (base) {
+        is A -> 1
+        is B -> 2
+        is E -> 3
+    }
+}
+
+fun test_ok_2(base: Base) {
+    val x = when (base) {
+        is A -> 1
+        is B.C -> 2
+        is B.D -> 3
+        E.First -> 4
+        E.Second -> 5
+    }
+}
+
+fun test_error_1(base: Base) {
+    val x = <!NO_ELSE_IN_WHEN!>when<!> (base) {
+        is A -> 1
+        is B -> 2
+    }
+}
+
+fun test_error_2(base: Base) {
+    val x = <!NO_ELSE_IN_WHEN!>when<!> (base) {
+        is A -> 1
+        is B.C -> 2
+        is B.D -> 3
+        E.Second -> 5
+    }
+}
+
+fun test_error_3(base: Base) {
+    val x = <!NO_ELSE_IN_WHEN!>when<!> (base) {
+        is A -> 1
+        is B.C -> 2
+        E.First -> 4
+        E.Second -> 5
+    }
+}