Add various tests for DFA testing

compiler/tests-spec/testData/diagnostics/notLinked/dfa/pos/60.kt

@@ -0,0 +1,25 @@
+// !LANGUAGE: +NewInference
+// !DIAGNOSTICS: -UNUSED_EXPRESSION -UNUSED_PARAMETER -UNUSED_VARIABLE -UNUSED_VALUE -VARIABLE_WITH_REDUNDANT_INITIALIZER
+// SKIP_TXT
+
+/*
+ * KOTLIN DIAGNOSTICS NOT LINKED SPEC TEST (POSITIVE)
+ *
+ * SECTIONS: dfa
+ * NUMBER: 60
+ * DESCRIPTION: Raw data flow analysis test
+ * HELPERS: classes, objects, typealiases, functions, enumClasses, interfaces, sealedClasses
+ */
+
+// TESTCASE NUMBER: 1
+fun case_1() {
+    var x: String? = null
+
+    outer@ while (x != null) {
+        inner@ do {
+            x = null
+        } while (x == null)
+        <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.String & kotlin.String?")!>x<!>
+        <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.String & kotlin.String?"), DEBUG_INFO_SMARTCAST!>x<!>.length
+    }
+}