[FIR-TEST] Add new testdata generated after changes in previous commit

compiler/testData/diagnostics/tests/nullabilityAndSmartCasts/kt1778.fir.kt

@@ -0,0 +1,12 @@
+// !CHECK_TYPE
+//KT-1778 Automatically cast error
+package kt1778
+
+fun main(args : Array<String>) {
+    val x = checkSubtype<Any>(args[0])
+    if(x is java.lang.CharSequence) {
+        if ("a" == x) x.<!UNRESOLVED_REFERENCE!>length<!> else x.length() // OK
+        if ("a" == x || "b" == x) x.<!UNRESOLVED_REFERENCE!>length<!> else x.length() // <– THEN ERROR
+        if ("a" == x && "a" == x) x.<!UNRESOLVED_REFERENCE!>length<!> else x.length() // <– ELSE ERROR
+    }
+}