From 23630af7b58a76a3d9882b4e876ba75ae4cd71c7 Mon Sep 17 00:00:00 2001
From: Tagir Valeev <Tagir.Valeev@jetbrains.com>
Date: Thu, 26 Jul 2018 11:27:01 +0700
Subject: [PATCH] ControlFlowAnalyzer: Enable math evaluation in for loop
 initializer

Fixes IDEA-195855 Incorrect NPE warning in reversed indexed for loop
---
 .../codeInspection/dataFlow/ControlFlowAnalyzer.java |  6 +++++-
 .../inspection/dataFlow/fixture/LongRangeBasics.java | 12 ++++++++++++
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/ControlFlowAnalyzer.java b/java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/ControlFlowAnalyzer.java
index e3c0f5f08396..6713b7eeb980 100644
--- a/java/java-analysis-impl/src/com/intellij/codeInspection/dataFlow/ControlFlowAnalyzer.java
+++ b/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;
diff --git a/java/java-tests/testData/inspection/dataFlow/fixture/LongRangeBasics.java b/java/java-tests/testData/inspection/dataFlow/fixture/LongRangeBasics.java
index e9f2e9d81c82..8ab2b4b36734 100644
--- a/java/java-tests/testData/inspection/dataFlow/fixture/LongRangeBasics.java
+++ b/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();
+      }
+    }
+  }
 }