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

compiler/testData/diagnostics/tests/smartCasts/kt3993.fir.kt

@@ -0,0 +1,10 @@
+class User(val login : Boolean) {}
+
+fun currentAccess(user: User?): Int {
+    return when {
+        user == null -> 0
+        // We should get smartcast here
+        user.login -> 1 
+        else -> -1
+    }
+}