Fix regression on smart casts in when on a sealed class

See the comment in PatternMatchingTypingVisitor

 #KT-27221 Fixed

compiler/testData/diagnostics/tests/smartCasts/kt27221.kt

@@ -0,0 +1,28 @@
+// !DIAGNOSTICS: -UNUSED_VARIABLE
+// SKIP_TXT
+
+sealed class A
+sealed class B : A()
+sealed class C : B()
+object BB : B()
+object CC : C()
+
+fun foo(a: A) {
+    if (a is B) {
+        if (a is C) {
+            val t = when (<!DEBUG_INFO_SMARTCAST!>a<!>) {
+                is CC -> "CC"
+            }
+        }
+    }
+}
+
+fun foo2(a: A) {
+    if (a is C) {
+        if (<!USELESS_IS_CHECK!>a is B<!>) {
+            val t = when (<!DEBUG_INFO_SMARTCAST!>a<!>) {
+                is CC -> "CC"
+            }
+        }
+    }
+}

compiler/testData/diagnostics/tests/smartCasts/kt27221_2.kt

@@ -0,0 +1,36 @@
+// !DIAGNOSTICS: -UNUSED_VARIABLE
+// SKIP_TXT
+
+sealed class A
+sealed class B : A()
+sealed class C : B()
+sealed class D : C()
+object BB : B()
+object CC : C()
+object DD : D()
+
+fun foo1(a: A) {
+    if (a is B) {
+        if (a is D) {
+            if (<!USELESS_IS_CHECK!>a is C<!>) {
+                val t =
+                    when (<!DEBUG_INFO_SMARTCAST!>a<!>) {
+                        is DD -> "DD"
+                    }
+            }
+        }
+    }
+}
+
+fun foo2(a: A) {
+    if (a is B) {
+        if (a is D) {
+            if (<!USELESS_IS_CHECK!>a is C<!>) {
+                val t =
+                    when (<!DEBUG_INFO_SMARTCAST!>a<!>) {
+                        is DD -> "DD"
+                    }
+            }
+        }
+    }
+}

compiler/testData/diagnostics/tests/smartCasts/kt27221_irrelevantClasses.kt

@@ -0,0 +1,28 @@
+// !DIAGNOSTICS: -UNUSED_VARIABLE
+// SKIP_TXT
+
+sealed class A
+sealed class B : A()
+sealed class C : A()
+object BB : B()
+object CC : C()
+
+fun foo(a: A) {
+    if (a is B) {
+        if (a is C) {
+            val t = when (<!DEBUG_INFO_SMARTCAST!>a<!>) {
+                is CC -> "CC"
+            }
+        }
+    }
+}
+
+fun foo2(a: A) {
+    if (a is C) {
+        if (a is B) {
+            val t = <!NO_ELSE_IN_WHEN!>when<!> (<!DEBUG_INFO_SMARTCAST!>a<!>) {
+                    is CC -> "CC"
+            }
+        }
+    }
+}