redundant cast: process multidimensional arrays (IDEA-171047)

java/java-psi-api/src/com/intellij/psi/util/RedundantCastUtil.java

@@ -738,7 +738,18 @@ public class RedundantCastUtil {
       PsiExpression lExpression = assignment.getLExpression();
       return lExpression instanceof PsiArrayAccessExpression &&
              PsiTreeUtil.isAncestor(lExpression, parent, false) &&
-             !PsiTreeUtil.isAncestor(((PsiArrayAccessExpression)lExpression).getIndexExpression(), element, false);
+             !isIndexExpression(element, (PsiArrayAccessExpression)lExpression);
+    }
+
+    private static boolean isIndexExpression(PsiElement element, PsiArrayAccessExpression arrayAccessExpression) {
+      if (PsiTreeUtil.isAncestor(arrayAccessExpression.getIndexExpression(), element, false)) {
+        return true;
+      }
+      PsiExpression arrayExpression = arrayAccessExpression.getArrayExpression();
+      if (arrayExpression instanceof PsiArrayAccessExpression) {
+        return isIndexExpression(element, (PsiArrayAccessExpression)arrayExpression);
+      }
+      return false;
     }
   }
 

java/java-tests/testData/inspection/redundantCast/lambda/CastInMultidimensionalArrayIndex.java

@@ -0,0 +1,5 @@
+class MyTest {
+  void bar(Object[] update, Object[][] grid){
+    grid[(int)update[0]][1] = null;
+  }
+}

java/java-tests/testSrc/com/intellij/codeInspection/RedundantCast18Test.java

@@ -41,4 +41,5 @@ public class RedundantCast18Test extends LightDaemonAnalyzerTestCase {
   public void testConditional() { doTest(); }
   public void testInferApplicabilityError() { doTest(); }
   public void testCastToRawType() { doTest(); }
+  public void testCastInMultidimensionalArrayIndex() { doTest(); }
 }