IDEA-87725 (Inspection catching "suspicious array casts" would be very useful)

plugins/InspectionGadgets/src/META-INF/plugin.xml

@@ -360,6 +360,10 @@
                      key="subtraction.in.compareto.display.name" groupBundle="messages.InspectionsBundle"
                      groupKey="group.names.probable.bugs" enabledByDefault="false" level="WARNING"
                      implementationClass="com.siyeh.ig.bugs.SubtractionInCompareToInspection"/>
+    <localInspection language="JAVA" shortName="SuspiciousArrayCast" bundle="com.siyeh.InspectionGadgetsBundle"
+                     key="suspicious.array.cast.display.name" groupBundle="messages.InspectionsBundle"
+                     groupKey="group.names.probable.bugs" enabledByDefault="false" level="WARNING"
+                     implementationClass="com.siyeh.ig.bugs.SuspiciousArrayCastInspection"/>
     <localInspection language="JAVA" shortName="SuspiciousIndentAfterControlStatement" bundle="com.siyeh.InspectionGadgetsBundle"
                      key="suspicious.indent.after.control.statement.display.name" groupBundle="messages.InspectionsBundle"
                      groupKey="group.names.probable.bugs" enabledByDefault="false" level="WARNING"

plugins/InspectionGadgets/src/com/siyeh/InspectionGadgetsBundle.properties

@@ -1974,3 +1974,5 @@ string.concatenation.missing.whitespace.option=Ignore when not both sides are st
 negated.equality.expression.display.name=Negated equality expression
 negated.equality.expression.problem.descriptor=Negating ''{0}'' #loc
 negated.equality.expression.quickfix=Remove negation
+suspicious.array.cast.display.name=Suspicious array cast
+suspicious.array.cast.problem.descriptor=Suspicious cast to <code>#ref</code>

plugins/InspectionGadgets/src/com/siyeh/ig/bugs/SuspiciousArrayCastInspection.java

@@ -0,0 +1,93 @@
+/*
+ * Copyright 2000-2012 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.siyeh.ig.bugs;
+
+import com.intellij.psi.*;
+import com.siyeh.InspectionGadgetsBundle;
+import com.siyeh.ig.BaseInspection;
+import com.siyeh.ig.BaseInspectionVisitor;
+import org.jetbrains.annotations.Nls;
+import org.jetbrains.annotations.NotNull;
+
+/**
+ * @author Bas Leijdekkers
+ */
+public class SuspiciousArrayCastInspection extends BaseInspection {
+
+  @Nls
+  @NotNull
+  @Override
+  public String getDisplayName() {
+    return InspectionGadgetsBundle.message("suspicious.array.cast.display.name");
+  }
+
+  @NotNull
+  @Override
+  protected String buildErrorString(Object... infos) {
+    return InspectionGadgetsBundle.message("suspicious.array.cast.problem.descriptor");
+  }
+
+  @Override
+  public BaseInspectionVisitor buildVisitor() {
+    return new SuspiciousArrayCastVisitor();
+  }
+
+  private static class SuspiciousArrayCastVisitor extends BaseInspectionVisitor {
+
+    @Override
+    public void visitTypeCastExpression(PsiTypeCastExpression expression) {
+      super.visitTypeCastExpression(expression);
+      final PsiTypeElement typeElement = expression.getCastType();
+      if (typeElement == null) {
+        return;
+      }
+      final PsiType castType = typeElement.getType();
+      if (!(castType instanceof PsiArrayType)) {
+        return;
+      }
+      final PsiExpression operand = expression.getOperand();
+      if (operand == null) {
+        return;
+      }
+      final PsiType type = operand.getType();
+      if (!(type instanceof PsiArrayType)) {
+        return;
+      }
+      final PsiType castComponentType = castType.getDeepComponentType();
+      if (!(castComponentType instanceof PsiClassType)) {
+        return;
+      }
+      final PsiClassType castClassType = (PsiClassType)castComponentType;
+      final PsiClass castClass = castClassType.resolve();
+      if (castClass == null) {
+        return;
+      }
+      final PsiType componentType = type.getDeepComponentType();
+      if (!(componentType instanceof PsiClassType)) {
+        return;
+      }
+      final PsiClassType classType = (PsiClassType)componentType;
+      final PsiClass aClass = classType.resolve();
+      if (aClass == null) {
+        return;
+      }
+      if (!castClass.isInheritor(aClass, true)) {
+        return;
+      }
+      registerError(typeElement);
+    }
+  }
+}

plugins/InspectionGadgets/src/inspectionDescriptions/SuspiciousArrayCast.html

@@ -0,0 +1,9 @@
+<html>
+<body>
+This inspection reports suspicious array casts. An array cast is suspicious when it casts to a more specific array type. Such
+a cast is legal at compile time but may fail with a <b>ClassCastException</b> at runtime.
+<!-- tooltip end -->
+<p>
+<small>New in 12, Powered by InspectionGadgets</small>
+</body>
+</html>

plugins/InspectionGadgets/test/com/siyeh/igtest/bugs/suspicious_array_cast/SuspiciousArrayCast.java

@@ -0,0 +1,11 @@
+package com.siyeh.igtest.bugs.suspicious_array_cast;
+
+class SuspiciousArrayCast {
+
+  private Long[] longs = (Long[])getNumbers();
+  private Number[] numbers = (Number[])getNumbers();
+
+  private Number[] getNumbers() {
+    return new Number[]{1L, 2L, 4L};
+  }
+}

plugins/InspectionGadgets/test/com/siyeh/igtest/bugs/suspicious_array_cast/expected.xml

@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<problems>
+  <problem>
+    <file>SuspiciousArrayCast.java</file>
+    <line>5</line>
+    <problem_class severity="WARNING" attribute_key="WARNING_ATTRIBUTES">Suspicious array cast</problem_class>
+    <description>Suspicious cast to &lt;code&gt;Long[]&lt;/code&gt;</description>
+  </problem>
+</problems>

plugins/InspectionGadgets/testsrc/com/siyeh/ig/bugs/SuspiciousArrayCastInspectionTest.java

@@ -0,0 +1,10 @@
+package com.siyeh.ig.bugs;
+
+import com.siyeh.ig.IGInspectionTestCase;
+
+public class SuspiciousArrayCastInspectionTest extends IGInspectionTestCase {
+
+  public void test() throws Exception {
+    doTest("com/siyeh/igtest/bugs/suspicious_array_cast", new SuspiciousArrayCastInspection());
+  }
+}