fix: report a missing class name as a syntax error

A class declaration with no name did not produce a SyntaxError:

    class {}      no message resource found for message id: parser.error.expected.ident
    class 1 {}    same

className() asked for the message key parser.error.expected.ident, which does
not exist. ECMAErrors.getMessage turns the MissingResourceException into a plain
RuntimeException, so the error was neither a ParserException nor - under
JSR-223 - a ScriptException.

There is no need for a new key: this is the same "Expected X but found Y" that
expectDontAdvance reports everywhere else, so className() now builds it the same
way, through the existing "expected" key. That also fixes the argument, which
named the token being looked at rather than the one that was wrong: the message
said "class" where the offending token was "{".

    class {}      Expected ident but found {
    class 1 {}    Expected ident but found 1

Two error tests come with it. Neither a malformed class name nor a duplicated
constructor had one, which is why a message key that never resolved could ship.
The duplicate-constructor message was already correct and is now covered.

./gradlew build testOptimistic testPessimistic:

  suite            before         after
  test             665, 0 fail    665, 0 fail
  testOptimistic   1715, 0 fail   1717, 0 fail
  testPessimistic  1715, 0 fail   1717, 0 fail

Author: marevol

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 }
+}
+^