Code sample:

public class Main {
  public static void main(String[] args) {
    sealed s = "s";
    System.out.println(s);
  }
}

Compile with --enable-preview, or just run `java` on this file. E.g:
"C:\Program Files\Java\jdk-16\bin\java.exe" --enable-preview --source=16 Main.java

Expected:
Compilation error at line #3

Actual:
Successfully compiled and launched, as if `sealed` were `var`.