IG: new "Class directly extends 'java.lang.Throwable'" inspection

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

@@ -860,6 +860,9 @@
                      level="WARNING" implementationClass="com.siyeh.ig.encapsulation.UseOfAnotherObjectsPrivateFieldInspection"/>
 
     <!--group.names.error.handling-->
+    <localInspection groupPath="Java" language="JAVA" shortName="ExtendsThrowable" bundle="com.siyeh.InspectionGadgetsBundle"
+                     key="extends.throwable.display.name" groupBundle="messages.InspectionsBundle" groupKey="group.names.error.handling"
+                     enabledByDefault="false" level="WARNING" implementationClass="com.siyeh.ig.errorhandling.ExtendsThrowableInspection"/>
     <localInspection groupPath="Java" language="JAVA" suppressId="ProhibitedExceptionCaught" shortName="BadExceptionCaught" bundle="com.siyeh.InspectionGadgetsBundle"
                      key="bad.exception.caught.display.name" groupBundle="messages.InspectionsBundle" groupKey="group.names.error.handling"
                      enabledByDefault="false" level="WARNING"

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

@@ -2157,4 +2157,7 @@ equals.replaceable.by.objects.call.problem.descriptor=<code>#ref</code> replacea
 equals.replaceable.by.objects.call.quickfix=Replace with 'Objects.equals()' expression
 array.objects.equals.display.name='Objects.equals()' called on arrays
 array.objects.equals.problem.descriptor=<code>Objects.#ref()</code> on arrays should probably be 'Arrays.equals()' #loc
-array.objects.deep.equals.problem.descriptor=<code>Objects.#ref()</code> on arrays should probably be 'Arrays.deepEquals()' #loc
+array.objects.deep.equals.problem.descriptor=<code>Objects.#ref()</code> on arrays should probably be 'Arrays.deepEquals()' #loc
+extends.throwable.display.name=Class directly extends 'java.lang.Throwable'
+anonymous.extends.throwable.problem.descriptor=Anonymous class directly extends 'java.lang.Throwable' \#loc
+extends.throwable.problem.descriptor=class <code>\#ref</code> directly extends 'java.lang.Throwable' \#loc

plugins/InspectionGadgets/InspectionGadgetsAnalysis/src/com/siyeh/ig/errorhandling/ExtendsThrowableInspection.java

@@ -0,0 +1,73 @@
+/*
+ * Copyright 2000-2015 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.errorhandling;
+
+import com.intellij.psi.CommonClassNames;
+import com.intellij.psi.PsiAnonymousClass;
+import com.intellij.psi.PsiClass;
+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 ExtendsThrowableInspection extends BaseInspection {
+
+  @Nls
+  @NotNull
+  @Override
+  public String getDisplayName() {
+    return InspectionGadgetsBundle.message("extends.throwable.display.name");
+  }
+
+  @NotNull
+  @Override
+  protected String buildErrorString(Object... infos) {
+    final PsiClass aClass = (PsiClass)infos[0];
+    if (aClass instanceof PsiAnonymousClass) {
+      return InspectionGadgetsBundle.message("anonymous.extends.throwable.problem.descriptor");
+    } else {
+      return InspectionGadgetsBundle.message("extends.throwable.problem.descriptor");
+    }
+  }
+
+  @Override
+  public BaseInspectionVisitor buildVisitor() {
+    return new ExtendsThrowableVisitor();
+  }
+
+  private static class ExtendsThrowableVisitor extends BaseInspectionVisitor {
+
+    @Override
+    public void visitClass(@NotNull PsiClass aClass) {
+      if (aClass.isInterface() || aClass.isAnnotationType() || aClass.isEnum()) {
+        return;
+      }
+      final PsiClass superClass = aClass.getSuperClass();
+      if (superClass == null) {
+        return;
+      }
+      final String superclassName = superClass.getQualifiedName();
+      if (!CommonClassNames.JAVA_LANG_THROWABLE.equals(superclassName)) {
+        return;
+      }
+      registerClassError(aClass, aClass);
+    }
+  }
+}

plugins/InspectionGadgets/src/inspectionDescriptions/ExtendsThrowable.html

@@ -0,0 +1,12 @@
+<html>
+<body>
+Reports any classes which directly extend <b>java.lang.Throwable</b>.
+It is generally considered bad practice to extend <b>java.lang.Throwable</b> directly and
+it is usually enough to extend either <b>java.lang.RuntimeException</b> or <b>java.lang.Exception</b> or in special
+cases <b>java.lang.Error</b>.
+<!-- tooltip end -->
+<p>
+<small>New in 15</small>
+<p>
+</body>
+</html>

plugins/InspectionGadgets/test/com/siyeh/igtest/errorhandling/extends_throwable/ExtendsThrowable.java

@@ -0,0 +1,9 @@
+public class <warning descr="class 'ExtendsThrowable' directly extends 'java.lang.Throwable'">ExtendsThrowable</warning> extends Throwable {
+
+  void f() {
+    new <warning descr="Anonymous class directly extends 'java.lang.Throwable'">Throwable</warning>() {
+      void b() {}
+    };
+  }
+}
+class E1 extends Exception {}

plugins/InspectionGadgets/testsrc/com/siyeh/ig/errorhandling/ExtendsThrowableInspectionTest.java

@@ -0,0 +1,37 @@
+/*
+ * Copyright 2000-2015 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.errorhandling;
+
+import com.intellij.codeInspection.InspectionProfileEntry;
+import com.siyeh.ig.LightInspectionTestCase;
+import junit.framework.TestCase;
+import org.jetbrains.annotations.Nullable;
+
+/**
+ * @author Bas Leijdekkers
+ */
+public class ExtendsThrowableInspectionTest extends LightInspectionTestCase {
+
+  public void testExtendsThrowable() {
+    doTest();
+  }
+
+  @Nullable
+  @Override
+  protected InspectionProfileEntry getInspection() {
+    return new ExtendsThrowableInspection();
+  }
+}