Java: basic support for Valhalla Value Classes (IDEA-364548)

GitOrigin-RevId: 93b0394866aae35772ccc90e7de822af8a94c6ce

java/java-tests/testData/codeInsight/daemonCodeAnalyzer/valueClass/ValueClass.java

@@ -0,0 +1,25 @@
+value class One {
+
+  <error descr="Variable 'value' might not have been initialized">private int value</error>;
+
+  <error descr="Modifier 'synchronized' not allowed here">synchronized</error> void x() {}
+}
+value class Two extends <error descr="Cannot inherit from non-abstract value class 'One'">One</error> {}
+value class Three extends <error descr="Value classes may only extend abstract value classes or 'java.lang.Object'">java.util.ArrayList</error> {}
+abstract value class Four {}
+value class Five extends Four {}
+class Six extends Four {} // it's valid to extend a value class with an identity class
+<error descr="Modifier 'value' not allowed here">value</error> interface Seven {}
+<error descr="Modifier 'value' not allowed here">value</error> enum Eight {}
+value record Nine(int no) {}
+<error descr="Illegal combination of modifiers 'sealed' and 'final'">sealed</error> value class Ten {}
+<error descr="Modifier 'non-sealed' not allowed on classes that do not have a sealed superclass">non-sealed</error> value class Eleven {}
+abstract sealed value class Twelve {}
+value class Thirteen extends Twelve {
+  void x() {
+    synchronized (this) {
+      System.out.println();
+    }
+  }
+}
+