ControlFlowAnalyzer: Enable math evaluation in for loop initializer

Fixes IDEA-195855 Incorrect NPE warning in reversed indexed for loop

java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/ControlFlowAnalyzer.java

@@ -1388,7 +1388,11 @@ public class ControlFlowAnalyzer extends JavaElementVisitor {
       if (parent instanceof PsiBinaryExpression && RelationType.fromElementType(((PsiBinaryExpression)parent).getOperationTokenType()) != null) {
         return true;
       }
-      if (parent instanceof PsiLoopStatement) return false;
+      if (parent instanceof PsiLoopStatement &&
+          !(parent instanceof PsiForStatement &&
+            PsiTreeUtil.isAncestor(((PsiForStatement)parent).getInitialization(), expression, false))) {
+        return false;
+      }
       parent = parent.getParent();
     }
     return true;

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

@@ -202,4 +202,16 @@ public class LongRangeBasics {
       System.out.println(s2.<warning descr="Method invocation 'trim' may produce 'java.lang.NullPointerException'">trim</warning>());
     }
   }
+
+  void testLoopInitializer(List l) {
+    int count = l != null ? l.size() : 0;
+    for (int i = count - 1; i >= 0; i--) {
+      try {
+        Object o = l.get(i);
+      }
+      catch (Exception e) {
+        e.printStackTrace();
+      }
+    }
+  }
 }