IDEA-116229 (Invalid Warning: Contents of array 'longs' are written to, but never read)

plugins/InspectionGadgets/InspectionGadgetsAnalysis/src/com/siyeh/ig/bugs/MismatchedArrayReadWriteInspection.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2003-2011 Dave Griffith, Bas Leijdekkers
+ * Copyright 2003-2014 Dave Griffith, Bas Leijdekkers
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -22,6 +22,7 @@ import com.intellij.psi.util.PsiUtil;
 import com.siyeh.InspectionGadgetsBundle;
 import com.siyeh.ig.BaseInspection;
 import com.siyeh.ig.BaseInspectionVisitor;
+import com.siyeh.ig.psiutils.CloneUtils;
 import com.siyeh.ig.psiutils.VariableAccessUtils;
 import org.jetbrains.annotations.NonNls;
 import org.jetbrains.annotations.NotNull;
@@ -137,8 +138,7 @@ public class MismatchedArrayReadWriteInspection extends BaseInspection {
       if (VariableAccessUtils.arrayContentsAreAssigned(variable, context)) {
         return true;
       }
-      final PsiExpression initializer = variable.getInitializer();
-      if (initializer != null && !isDefaultArrayInitializer(initializer)) {
+      if (!isDefaultArrayInitializer(variable.getInitializer())) {
         return true;
       }
       return variableIsWritten(variable, context);
@@ -149,11 +149,39 @@ public class MismatchedArrayReadWriteInspection extends BaseInspection {
       if (VariableAccessUtils.arrayContentsAreAccessed(variable, context)) {
         return true;
       }
+      if (isPossiblyReferenceThatIsReadLater(variable.getInitializer())) {
+        return true;
+      }
       return variableIsRead(variable, context);
     }
 
-    private static boolean isDefaultArrayInitializer(
-      PsiExpression initializer) {
+    private static boolean isPossiblyReferenceThatIsReadLater(PsiExpression initializer) {
+      if (initializer == null || initializer instanceof PsiNewExpression || initializer instanceof PsiArrayInitializerExpression) {
+        return false;
+      }
+      if (initializer instanceof PsiMethodCallExpression) {
+        final PsiMethodCallExpression methodCallExpression = (PsiMethodCallExpression)initializer;
+        final PsiMethod method = methodCallExpression.resolveMethod();
+        if (method == null) {
+          return true;
+        }
+        if (CloneUtils.isClone(method)) {
+          return false;
+        }
+        @NonNls final String name = method.getName();
+        if (!"copyOf".equals(name) && !"copyOfRange".equals(name)) {
+          return true;
+        }
+        final PsiClass aClass = method.getContainingClass();
+        return aClass == null || !CommonClassNames.JAVA_UTIL_ARRAYS.equals(aClass.getQualifiedName());
+      }
+      return true;
+    }
+
+    private static boolean isDefaultArrayInitializer(PsiExpression initializer) {
+      if (initializer == null) {
+        return true;
+      }
       if (initializer instanceof PsiNewExpression) {
         final PsiNewExpression newExpression =
           (PsiNewExpression)initializer;

plugins/InspectionGadgets/test/com/siyeh/igtest/bugs/mismatched_array_read_write/MismatchedArrayReadWrite.java

@@ -117,3 +117,65 @@ class Test{
     return null;
   }
 }
+class Bug {
+  // Example 1
+  public void test1() {
+    final java.util.List<long[]> results = new java.util.ArrayList<>();
+    for (int i = 0; i < 10; i++) {
+      results.add(new long[3]);
+    }
+
+    for (int i = 0; i < results.size(); i++) {
+      final long[] longs = results.get(i); // <-- Contents of array 'longs' are written to, but never read
+      for (int j = 0; j < 3; j++) {
+        longs[j] = i * j;
+      }
+    }
+
+    for (long[] result : results) {
+      for (long l : result) {
+        System.out.println(l);
+      }
+    }
+  }
+
+  // Example 2
+  private int[] _ints = {0};
+
+  public void print() {
+    for (int i : _ints) {
+      System.out.println(i);
+    }
+  }
+
+  public void test2() {
+    final Bug bug = new Bug();
+    final int[] ints = bug._ints; // <-- Contents of array 'ints' are written to, but never read
+    ints[0] = 1;
+    bug.print();
+  }
+}
+class Toster
+{
+  private static final int MAX = 1;
+
+  public static void main(String[] args)
+  {
+    new Toster().run();
+  }
+
+  private int[][] values = new int[][] { {new java.util.Random().nextInt()}, {new java.util.Random().nextInt()} };
+
+  private void run()
+  {
+    for (int j = new java.util.Random().nextInt(values.length); j < new java.util.Random().nextInt(values.length); j++)
+    {
+      int[] array = values[j]; //IDEA says here: contents of array 'array' are written to, but never used
+
+      for (int i = 0; i < MAX; i++)
+      {
+        array[i] = new java.util.Random().nextInt();
+      }
+    }
+  }
+}