Add various tests for DFA testing

compiler/tests-spec/testData/diagnostics/notLinked/dfa/neg/40.kt

@@ -0,0 +1,32 @@
+// !LANGUAGE: +NewInference
+// !DIAGNOSTICS: -UNUSED_EXPRESSION -ASSIGNED_BUT_NEVER_ACCESSED_VARIABLE -UNUSED_PARAMETER -UNUSED_VARIABLE -UNUSED_VALUE -VARIABLE_WITH_REDUNDANT_INITIALIZER
+// SKIP_TXT
+
+/*
+ * KOTLIN DIAGNOSTICS NOT LINKED SPEC TEST (NEGATIVE)
+ *
+ * SECTIONS: dfa
+ * NUMBER: 40
+ * DESCRIPTION: Raw data flow analysis test
+ * HELPERS: classes, objects, typealiases, functions, enumClasses, interfaces, sealedClasses
+ */
+
+/*
+ * TESTCASE NUMBER: 1
+ * ISSUES: KT-8819
+ */
+fun case_1(x: Pair<*, *>) {
+    if (x.first !is String) return
+    <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Any?")!>x.first<!>
+    <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Any?")!>x.first<!>.<!UNRESOLVED_REFERENCE!>length<!>
+}
+
+/*
+ * TESTCASE NUMBER: 2
+ * ISSUES: KT-8819
+ */
+fun case_2(x: Pair<*, *>) {
+    if (x.first !is String?) throw Exception()
+    <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Any?")!>x.first<!>
+    <!DEBUG_INFO_EXPRESSION_TYPE("kotlin.Any?")!>x.first<!>?.<!UNRESOLVED_REFERENCE!>length<!>
+}