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

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

@@ -0,0 +1,29 @@
+open class A {
+    class B : A() {
+        val a = "FAIL"
+    }
+
+    class C : A() {
+        val a = "FATAL"
+    }
+
+    fun foo(): String {
+        if (this is B) return a
+        else if (this is C) return a
+        return "OK"
+    }
+}
+
+fun A?.bar() {
+    if (this != null) foo()
+}
+
+fun A.gav() = if (this is A.B) a else ""
+
+class C {
+    fun A?.complex(): String {
+        if (this is A.B) return a
+        else if (this != null) return foo()
+        else return ""
+    }
+}