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

compiler/testData/diagnostics/tests/controlFlowAnalysis/kt607.fir.kt

@@ -0,0 +1,18 @@
+//KT-607 Val reassignment is not marked as an error
+
+package kt607
+
+fun foo(a: A) {
+    val o = object {
+        val y : Int
+           get() = 42
+    }
+
+    a.z = 23
+    o.y = 11   //Should be an error here
+}
+
+class A() {
+    val z : Int
+    get() = 3
+}