dfa: add a test for assignment with side effects inside method calls (IDEA-145401, IDEA-CR-5542)

java/java-tests/testData/inspection/dataFlow/fixture/DontSimplifyAssignment.java

@@ -6,4 +6,14 @@ class Contracts {
     return x && <warning descr="Condition '!(x = false)' is always 'true' when reached">!(x =<caret> false)</warning>;
   }
 
+  public void testSideEffectInsideCall() {
+    if (a()) {
+      System.out.println();
+    }
+  }
+
+  private boolean a() {
+    return x = false;
+  }
+
 }