Issue #44: Detect dead instanceof-expressions

#44

src/main/java/de/markiewb/netbeans/plugins/hints/structure/WarnOfDeadInstanceOf.java

@@ -0,0 +1,115 @@
+/* 
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
+ *
+ * Copyright 2014 Oracle and/or its affiliates. All rights reserved.
+ *
+ * Oracle and Java are registered trademarks of Oracle and/or its affiliates.
+ * Other names may be trademarks of their respective owners.
+ *
+ * The contents of this file are subject to the terms of either the GNU
+ * General Public License Version 2 only ("GPL") or the Common
+ * Development and Distribution License("CDDL") (collectively, the
+ * "License"). You may not use this file except in compliance with the
+ * License. You can obtain a copy of the License at
+ * http://www.netbeans.org/cddl-gplv2.html
+ * or nbbuild/licenses/CDDL-GPL-2-CP. See the License for the
+ * specific language governing permissions and limitations under the
+ * License.  When distributing the software, include this License Header
+ * Notice in each file and include the License file at
+ * nbbuild/licenses/CDDL-GPL-2-CP.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the GPL Version 2 section of the License file that
+ * accompanied this code. If applicable, add the following below the
+ * License Header, with the fields enclosed by brackets [] replaced by
+ * your own identifying information:
+ * "Portions Copyrighted [year] [name of copyright owner]"
+ *
+ * If you wish your version of this file to be governed by only the CDDL
+ * or only the GPL Version 2, indicate your decision by adding
+ * "[Contributor] elects to include this software in this distribution
+ * under the [CDDL or GPL Version 2] license." If you do not indicate a
+ * single choice of license, a recipient has the option to distribute
+ * your version of this file under either the CDDL, the GPL Version 2 or
+ * to extend the choice of license to its licensees as provided above.
+ * However, if you add GPL Version 2 code and therefore, elected the GPL
+ * Version 2 license, then the option applies only if the new code is
+ * made subject to such option by the copyright holder.
+ *
+ * Contributor(s):
+ *
+ * Portions Copyrighted 2014 Sun Microsystems, Inc.
+ * Portions Copyrighted 2014 benno.markiewicz@googlemail.com
+ */
+package de.markiewb.netbeans.plugins.hints.structure;
+
+import com.sun.source.tree.InstanceOfTree;
+import com.sun.source.tree.Tree;
+import com.sun.source.util.TreePath;
+import javax.lang.model.element.Element;
+import javax.lang.model.element.TypeElement;
+import javax.lang.model.type.DeclaredType;
+import javax.lang.model.type.TypeKind;
+import javax.lang.model.type.TypeMirror;
+import org.netbeans.api.java.source.CompilationInfo;
+import org.netbeans.spi.editor.hints.ErrorDescription;
+import org.netbeans.spi.editor.hints.Severity;
+import org.netbeans.spi.java.hints.ErrorDescriptionFactory;
+import org.netbeans.spi.java.hints.Hint;
+import org.netbeans.spi.java.hints.HintContext;
+import org.netbeans.spi.java.hints.TriggerTreeKind;
+import org.openide.util.NbBundle;
+
+/**
+ * Detects instanceof-expressions, which will never be true.
+ *
+ * https://github.com/markiewb/nb-additional-hints/issues/44
+ *
+ * Code has been adopted from
+ * {@link org.netbeans.modules.java.hints.IllegalInstanceOf}
+ *
+ * @author markiewb
+ */
+@NbBundle.Messages({
+    "# {0} - first argument in instanceof operator",
+    "# {1} - second argument in instanceof operator",
+    "ERR_WarnOfDeadInstanceOf=Dead instanceof. {0} cannot be assigned to {1}",
+    "DN_WarnOfDeadInstanceOf=Dead instanceof",
+    "DESC_WarnOfDeadInstanceOf=Detects instanceof-expressions, which will never be true.<p>For example: <tt>new ArrayList() instanceof java.util.Set</tt> will be never be true.</p><p>Provided by <a href=\"https://github.com/markiewb/nb-additional-hints\">nb-additional-hints</a> plugin</p>"})
+public class WarnOfDeadInstanceOf {
+
+    @Hint(displayName = "#DN_WarnOfDeadInstanceOf", description = "#DESC_WarnOfDeadInstanceOf", category = "bugs",
+            hintKind = Hint.Kind.INSPECTION, severity = Severity.WARNING)
+    @TriggerTreeKind({Tree.Kind.INSTANCE_OF})
+    public static ErrorDescription convert(HintContext ctx) {
+
+        TreePath path = ctx.getPath();
+        TreePath treePath = ctx.getPath();
+        CompilationInfo info = ctx.getInfo();
+
+        InstanceOfTree iot = (InstanceOfTree) treePath.getLeaf();
+        TypeMirror leftTypeMirror = info.getTrees().getTypeMirror(new TreePath(treePath, iot.getExpression()));
+
+        if (leftTypeMirror == null || leftTypeMirror.getKind() != TypeKind.DECLARED) {
+            return null;
+        }
+
+        Element leftType = ((DeclaredType) leftTypeMirror).asElement();
+        Element rightType = info.getTrees().getElement(new TreePath(treePath, iot.getType()));
+
+        if (leftType == null || rightType == null) {
+            //we cannot handle this
+            return null;
+        }
+
+        final TypeMirror leftT = info.getTypes().erasure(((TypeElement) leftType).asType());
+        final TypeMirror rightT = info.getTypes().erasure(((TypeElement) rightType).asType());
+        //f.e. (new ArrayList() instanceof java.util.Set) is impossible
+        final boolean assignable = info.getTypes().isAssignable(leftT, rightT);
+        if (!assignable) {
+            return ErrorDescriptionFactory.forName(ctx, path, Bundle.ERR_WarnOfDeadInstanceOf(leftType.getSimpleName().toString(), rightType.getSimpleName().toString()));
+        }
+
+        return null;
+
+    }
+}

src/test/java/de/markiewb/netbeans/plugins/hints/structure/WarnOfDeadInstanceOfTest.java

@@ -0,0 +1,42 @@
+package de.markiewb.netbeans.plugins.hints.structure;
+
+import org.junit.Test;
+import org.netbeans.modules.java.hints.test.api.HintTest;
+
+public class WarnOfDeadInstanceOfTest {
+
+    @Test
+    public void testMatchingCases() throws Exception {
+        /**
+         * <pre>
+         * //negative cases -> error hint for instance of
+         * if (new java.util.ArrayList() instanceof java.util.Map) {}
+         * if (new java.util.ArrayList() instanceof java.util.Set) {}
+         * if (new java.util.ArrayList<String>() instanceof java.util.Set) {}
+         * //positive cases
+         * if (new java.util.ArrayList() instanceof java.util.List) {}
+         * if (new java.util.HashSet() instanceof java.util.Set) {}
+         * if (new java.util.HashSet<String>() instanceof java.util.Set) {}
+         * </pre>
+         */
+        HintTest.create()
+                .input(
+                        "package example;\n"
+                        + "public class Test {\n"
+                        + "    void getMember(){\n"
+                        + "         //negative cases -> error hint for instance of\n"
+                        + "         if (new java.util.ArrayList() instanceof java.util.Map) {}\n"
+                        + "         if (new java.util.ArrayList() instanceof java.util.Set) {}\n"
+                        + "         if (new java.util.ArrayList<String>() instanceof java.util.Set) {}\n"
+                        + "         //positive cases\n"
+                        + "         if (new java.util.ArrayList() instanceof java.util.List) {}\n"
+                        + "         if (new java.util.HashSet() instanceof java.util.Set) {}\n"
+                        + "         if (new java.util.HashSet<String>() instanceof java.util.Set) {}\n"
+                        + "    };\n"
+                        + "}"
+                )
+                .run(WarnOfDeadInstanceOf.class)
+                .assertWarnings("4:13-4:63:warning:" + Bundle.ERR_WarnOfDeadInstanceOf("ArrayList", "Map"), "5:13-5:63:warning:" + Bundle.ERR_WarnOfDeadInstanceOf("ArrayList", "Set"), "6:13-6:71:warning:" + Bundle.ERR_WarnOfDeadInstanceOf("ArrayList", "Set"));
+    }
+
+}

src/test/java/example/DeadInstanceOfExample.java

@@ -0,0 +1,15 @@
+package example;
+
+public class DeadInstanceOfExample {
+
+    public void test() {
+        //negative cases -> error hint for instance of
+        if (new java.util.ArrayList() instanceof java.util.Map) {}
+        if (new java.util.ArrayList() instanceof java.util.Set) {}
+        if (new java.util.ArrayList<String>() instanceof java.util.Set) {}
+        //positive cases
+        if (new java.util.ArrayList() instanceof java.util.List) {}
+        if (new java.util.HashSet() instanceof java.util.Set) {}
+        if (new java.util.HashSet<String>() instanceof java.util.Set) {}
+    }
+}