feat: implement user values

src/main/java/me/topchetoeu/jscript/runtime/values/functions/Arguments.java

@@ -3,6 +3,7 @@ package me.topchetoeu.jscript.runtime.values.functions;
 
 import me.topchetoeu.jscript.common.environment.Environment;
 import me.topchetoeu.jscript.runtime.values.Value;
+import me.topchetoeu.jscript.runtime.values.primitives.UserValue;
 
 public class Arguments {
     public final Value self;
@@ -21,6 +22,11 @@ public class Arguments {
     public Value self() {
         return get(-1);
     }
+    @SuppressWarnings("unchecked")
+	public <T> T self(Class<T> clazz) {
+		if (self instanceof UserValue user && clazz.isInstance(user.value)) return (T)user.value;
+		else return null;
+    }
     public Value get(int i) {
         if (i >= args.length || i < -1) return Value.UNDEFINED;
         else if (i == -1) return self;

src/main/java/me/topchetoeu/jscript/runtime/values/primitives/UserValue.java

@@ -0,0 +1,69 @@
+package me.topchetoeu.jscript.runtime.values.primitives;
+
+import java.util.Arrays;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Objects;
+import java.util.Set;
+
+import me.topchetoeu.jscript.common.environment.Environment;
+import me.topchetoeu.jscript.runtime.values.KeyCache;
+import me.topchetoeu.jscript.runtime.values.Member;
+import me.topchetoeu.jscript.runtime.values.Value;
+import me.topchetoeu.jscript.runtime.values.objects.ObjectValue;
+import me.topchetoeu.jscript.runtime.values.primitives.numbers.NumberValue;
+
+public final class UserValue<T> extends Value {
+    public final T value;
+	public final ObjectValue prototype;
+
+    @Override public StringValue type() { return StringValue.of("object"); }
+
+    @Override public boolean toBoolean() { return true; }
+    @Override public NumberValue toNumber(Environment ext) { return NumberValue.NAN; }
+    @Override public String toString(Environment ext) { return "[user value]"; }
+
+    @Override public final boolean defineOwnMember(Environment env, KeyCache key, Member member) { return false; }
+    @Override public final boolean deleteOwnMember(Environment env, KeyCache key) { return false; }
+    @Override public final boolean isPrimitive() { return false; }
+    @Override public final Value toPrimitive(Environment env) { return NumberValue.NAN; }
+
+    @Override public final boolean setPrototype(Environment env, ObjectValue val) { return false; }
+
+    @Override public Member getOwnMember(Environment env, KeyCache key) { return null; }
+    @Override public Set<String> getOwnMembers(Environment env, boolean onlyEnumerable) { return new HashSet<>(); }
+    @Override public Set<SymbolValue> getOwnSymbolMembers(Environment env, boolean onlyEnumerable) { return new HashSet<>(); }
+
+    @Override public State getState() { return State.FROZEN; }
+
+    @Override public void preventExtensions() {}
+    @Override public void seal() {}
+    @Override public void freeze() {}
+
+	@Override public int hashCode() {
+		return value.hashCode();
+	}
+    @Override public boolean equals(Object other) {
+        if (this == other) return true;
+        else if (other instanceof UserValue val) return Objects.equals(value, val.value);
+        else return false;
+    }
+
+    @Override public ObjectValue getPrototype(Environment env) { return prototype; }
+
+    @Override public List<String> toReadableLines(Environment env, HashSet<ObjectValue> passed) {
+        return Arrays.asList(value.toString());
+    }
+
+    private UserValue(T value, ObjectValue prototype) {
+        this.value = value;
+		this.prototype = prototype;
+    }
+
+    public static <T> UserValue<T> of(T value) {
+		return new UserValue<T>(value, null);
+    }
+    public static <T> UserValue<T> of(T value, ObjectValue prototype) {
+		return new UserValue<T>(value, prototype);
+    }
+}