fix: report a missing class name as a syntax error

src/main/java/org/codelibs/sai/internal/parser/Parser.java

@@ -1119,7 +1119,9 @@ private IdentNode className() {
         final int nameIndex = k + 1;
 
         if (T(nameIndex) != IDENT) {
-            throw error(AbstractParser.message("expected.ident", type.getNameOrType()), getToken(nameIndex));
+            final long nameToken = getToken(nameIndex);
+            throw error(AbstractParser.message("expected", IDENT.getNameOrType(), Token.toString(source, nameToken)),
+                    nameToken);
         }
 
         return createIdentNode(getToken(nameIndex), finish, (String) getValue(getToken(nameIndex)));

test/script/error/class_duplicate_constructor.js

@@ -0,0 +1,32 @@
+/*
+ * Copyright (c) 2026, CodeLibs Project and/or its affiliates. All rights reserved.
+ *
+ * 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.
+ */
+
+/**
+ * A class body may define at most one constructor.
+ *
+ * @test/compile-error
+ * @option --language=es6
+ */
+
+class Point {
+    constructor() {
+    }
+
+    constructor() {
+    }
+}

test/script/error/class_duplicate_constructor.js.EXPECTED

@@ -0,0 +1,6 @@
+test/script/error/class_duplicate_constructor.js:30:4 A class may only have one constructor
+    constructor() {
+    ^
+test/script/error/class_duplicate_constructor.js:31:4 Expected eof but found }
+    }
+    ^

test/script/error/class_name_missing.js

@@ -0,0 +1,28 @@
+/*
+ * Copyright (c) 2026, CodeLibs Project and/or its affiliates. All rights reserved.
+ *
+ * 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.
+ */
+
+/**
+ * A class declaration needs a name. Saying so has to be an ordinary syntax error
+ * rather than a missing message resource.
+ *
+ * @test/compile-error
+ * @option --language=es6
+ */
+
+class {
+}

test/script/error/class_name_missing.js.EXPECTED

@@ -0,0 +1,6 @@
+test/script/error/class_name_missing.js:27:6 Expected ident but found {
+class {
+      ^
+test/script/error/class_name_missing.js:28:0 Expected eof but found }
+}
+^