From 3457fe2b552abdd9edfb41bf6752c41495177e7c Mon Sep 17 00:00:00 2001
From: Tagir Valeev <Tagir.Valeev@jetbrains.com>
Date: Tue, 11 Apr 2017 10:29:15 +0700
Subject: [PATCH] IDEA-168715 Dead code inspection doesn't work in loop
 (Conservatively handle including bound)

---
 .../dataFlow/ControlFlowAnalyzer.java         |  7 ++++-
 .../dataFlow/fixture/LongRangeLoop.java       | 26 ++++++++++++++++++-
 2 files changed, 31 insertions(+), 2 deletions(-)

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 bd05e8cb8da9..9407a57d5aec 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
@@ -514,8 +514,13 @@ public class ControlFlowAnalyzer extends JavaElementVisitor {
   private void addCountingLoopBound(PsiForStatement statement) {
     CountingLoop loop = CountingLoop.from(statement);
     if (loop == null) return;
-    // Add known-to-be-true condition inside counting loop, effectively converting
     PsiLocalVariable counter = loop.getCounter();
+    if (loop.isIncluding() && !(PsiType.LONG.equals(counter.getType()) && PsiType.INT.equals(loop.getBound().getType()))) {
+      Object bound = ExpressionUtils.computeConstantExpression(loop.getBound());
+      // could be for(int i=0; i<=Integer.MAX_VALUE; i++) which will overflow: conservatively skip this
+      if (!(bound instanceof Number)) return;
+      if (bound.equals(Long.MAX_VALUE) || bound.equals(Integer.MAX_VALUE)) return;
+    }
     PsiExpression initializer = loop.getInitializer();
     if (!PsiType.INT.equals(initializer.getType()) && !PsiType.LONG.equals(initializer.getType())) return;
     DfaValue origin = null;
diff --git a/java/java-tests/testData/inspection/dataFlow/fixture/LongRangeLoop.java b/java/java-tests/testData/inspection/dataFlow/fixture/LongRangeLoop.java
index d37e6dd7d8e5..755042414fff 100644
--- a/java/java-tests/testData/inspection/dataFlow/fixture/LongRangeLoop.java
+++ b/java/java-tests/testData/inspection/dataFlow/fixture/LongRangeLoop.java
@@ -25,7 +25,7 @@ public class LongRangeLoop {
 
   public static void loopOrigin(long i) {
     if(i > 0) {
-      for(long j = i; j < 1000; ++j) {
+      for (long j = i; j <= 1000; ++j) {
         if (<warning descr="Condition 'j < 0' is always 'false'">j < 0</warning>) {
           System.out.println("Impossible");
         }
@@ -33,6 +33,30 @@ public class LongRangeLoop {
     }
   }
 
+  public static void loopUnknownBoundIncluding(int bound) {
+    for (int i = 0; i <= bound; i++) {
+      if (i == -1) {
+        System.out.println("Overflow detected: bound was Integer.MAX_VALUE");
+      }
+    }
+  }
+
+  public static void loopUnknownBoundExcluding(int bound) {
+    for (int i = 0; i < bound; i++) {
+      if (<warning descr="Condition 'i == -1' is always 'false'">i == -1</warning>) {
+        System.out.println("Impossible even if bound is Integer.MAX_VALUE");
+      }
+    }
+  }
+
+  public static void loopUnknownBoundIncludingLong(int bound) {
+    for (long i = 0; i <= bound; i++) {
+      if (<warning descr="Condition 'i == -1' is always 'false'">i == -1</warning>) {
+        System.out.println("Impossible even if bound is Integer.MAX_VALUE");
+      }
+    }
+  }
+
   public void IDEA168715() {
     for (int i = 1; i < 100; i++) {
       if (<warning descr="Condition 'i == 0' is always 'false'">i == 0</warning>) {