From c25786fabf822186bb71eab01902c2b0283a6c9a Mon Sep 17 00:00:00 2001
From: "Roman.Ivanov" <Roman.Ivanov@jetbrains.com>
Date: Fri, 4 May 2018 15:17:04 +0700
Subject: [PATCH] ManualArrayCopyInspection: prevent changing semantics :
 IDEA-52481

---
 .../ig/performance/ManualArrayCopyInspection.java     | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/plugins/InspectionGadgets/InspectionGadgetsAnalysis/src/com/siyeh/ig/performance/ManualArrayCopyInspection.java b/plugins/InspectionGadgets/InspectionGadgetsAnalysis/src/com/siyeh/ig/performance/ManualArrayCopyInspection.java
index 7912cf8117b0..9c23174a9511 100644
--- a/plugins/InspectionGadgets/InspectionGadgetsAnalysis/src/com/siyeh/ig/performance/ManualArrayCopyInspection.java
+++ b/plugins/InspectionGadgets/InspectionGadgetsAnalysis/src/com/siyeh/ig/performance/ManualArrayCopyInspection.java
@@ -16,6 +16,7 @@
 package com.siyeh.ig.performance;
 
 import com.intellij.codeInspection.ProblemDescriptor;
+import com.intellij.codeInspection.dataFlow.DfaUtil;
 import com.intellij.openapi.project.Project;
 import com.intellij.psi.*;
 import com.intellij.psi.tree.IElementType;
@@ -84,7 +85,13 @@ public class ManualArrayCopyInspection extends BaseInspection {
       if (newExpression == null) {
         return;
       }
-      PsiReplacementUtil.replaceStatement(forStatement, newExpression, commentTracker);
+      PsiIfStatement ifStatement = (PsiIfStatement)commentTracker.replaceAndRestoreComments(forStatement, newExpression);
+      if (Boolean.TRUE.equals(DfaUtil.evaluateCondition(ifStatement.getCondition())))  {
+        PsiStatement nakedSubListClear = ControlFlowUtils.stripBraces(ifStatement.getThenBranch());
+        assert nakedSubListClear != null;
+        CommentTracker ct = new CommentTracker();
+        ct.replaceAndRestoreComments(ifStatement, ct.markUnchanged(nakedSubListClear));
+      }
     }
 
     @Nullable
@@ -161,7 +168,7 @@ public class ManualArrayCopyInspection extends BaseInspection {
       final String toOffsetText = buildOffsetText(strippedLhsIndexExpression, variable,
                                                   limitExpression, decrement && (JavaTokenType.LT.equals(tokenType) || JavaTokenType.GT.equals(tokenType)),
                                                   commentTracker);
-      return "System.arraycopy(" + fromArrayText + ", " + fromOffsetText + ", " + toArrayText + ", " + toOffsetText + ", " + lengthText + ");";
+      return "if(" + lengthText + ">=0)" + "System.arraycopy(" + fromArrayText + ", " + fromOffsetText + ", " + toArrayText + ", " + toOffsetText + ", " + lengthText + ");";
     }
 
     @Nullable