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

compiler/testData/diagnostics/tests/dataFlowInfoTraversal/AssignmentOperation.fir.kt

@@ -0,0 +1,17 @@
+// !CHECK_TYPE
+
+fun bar1(x: Number, y: Int) {
+    var yy = y
+    yy += x as Int
+    checkSubtype<Int>(x)
+}
+
+fun bar2(x: Number) {
+    <!UNRESOLVED_REFERENCE, VARIABLE_EXPECTED!>y<!> += x as Int
+    checkSubtype<Int>(x)
+}
+
+fun bar3(x: Number, y: Array<Int>) {
+    y[0] += x as Int
+    checkSubtype<Int>(x)
+}