6921495: spurious semicolons in class def cause empty NOPOS blocks

Reviewed-by: mcimadamore

langtools/src/share/classes/com/sun/tools/javac/parser/JavacParser.java

@@ -2781,7 +2781,7 @@ public class JavacParser implements Parser {
     List<JCTree> classOrInterfaceBodyDeclaration(Name className, boolean isInterface) {
         if (S.token() == SEMI) {
             S.nextToken();
-            return List.<JCTree>of(F.at(Position.NOPOS).Block(0, List.<JCStatement>nil()));
+            return List.<JCTree>nil();
         } else {
             String dc = S.docComment();
             int pos = S.pos();

langtools/test/tools/javac/parser/ExtraSemiTest.java

@@ -0,0 +1,100 @@
+/*
+ * Copyright (c) 2010, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+/*
+ * @test
+ * @bug 6921495
+ * @summary spurious semicolons in class def cause empty NOPOS blocks
+ */
+
+import java.io.*;
+import java.net.*;
+import java.util.*;
+import javax.tools.*;
+import com.sun.source.util.*;
+
+public class ExtraSemiTest {
+
+    static class JavaSource extends SimpleJavaFileObject {
+
+        final static String source =
+                        "class C {\n" +
+                        "    int x;;\n" +
+                        "    class X { int i;; };\n" +
+                        "}";
+
+        JavaSource() {
+            super(URI.create("myfo:/C.java"), JavaFileObject.Kind.SOURCE);
+        }
+
+        @Override
+        public CharSequence getCharContent(boolean ignoreEncodingErrors) {
+            return source;
+        }
+    }
+
+    public static void main(String... args) throws IOException {
+        new ExtraSemiTest().run();
+    }
+
+    void run() throws IOException {
+        File destDir = new File("classes"); destDir.mkdir();
+        final JavaCompiler tool = ToolProvider.getSystemJavaCompiler();
+        JavaSource source = new JavaSource();
+        JavacTask ct = (JavacTask)tool.getTask(null, null, null,
+                Arrays.asList("-d", destDir.getPath(), "-XD-printsource"),
+                null,
+                Arrays.asList(source));
+        Boolean ok = ct.call();
+        if (!ok) throw new AssertionError("compilation failed");
+
+        String text = readFile(new File(destDir, "C.java"));
+        System.out.println(text);
+
+        // compress/canonicalize all whitespace
+        String canon = text.replaceAll("\\s+", " ");
+        System.out.println("canon: " + canon);
+
+        // There are no empty blocks in the original text.
+        // C will be given a default constructor "C() { super(); }" which
+        // does not have any empty blocks.
+        // The bug is that spurious semicolons in the class defn are parsed
+        // into redundant empty blocks in the tree, so verify there are
+        // no empty blocks in the -printsource output
+
+        if (canon.contains("{ }"))
+            throw new AssertionError("unexpected empty block found");
+    }
+
+    String readFile(File f) throws IOException {
+        int len = (int) f.length();
+        byte[] data = new byte[len];
+        DataInputStream in = new DataInputStream(new FileInputStream(f));
+        try {
+            in.readFully(data);
+            return new String(data);
+        } finally {
+            in.close();
+        }
+    }
+}