Why does Truffle DSL makes an error when adding @Specialization annotations?

Question

I am trying to implement the Truffle Framework into an existing language (INI) and I managed to run the language with basic features and Truffle. However, when I try to add @Specialization annotations to my methods, the compiler crashes and outputs this message :

src/main/java/ini/eval/function/PrintFunction.java:[17,17] Not enough child node declarations found. Please annotate the node class with addtional @NodeChild annotations or remove all execute methods that do not provide all evaluated values. The following execute methods do not provide all evaluated values for the expected signature size 1: [executeGeneric(VirtualFrame), executeNumber(VirtualFrame), executeBoolean(VirtualFrame), executeChar(VirtualFrame), executeString(VirtualFrame)]

However, when I remove the @Specialization annotation, it works fine

This is the only class where I've put specialization yet :

@NodeInfo(shortName = "print")
@GenerateNodeFactory()
public abstract class PrintFunction extends BuiltInExecutable {

    public PrintFunction(IniParser parser, String name, String[] parameterNames) {
        super();
    }

    private static final PrintStream out = System.out;

    @Specialization
    public Number print(Number value) {
        doPrint(value);
        return value;
    }

    @TruffleBoundary
    private static void doPrint(Number value) {
        out.print(value);
    }

    ... More specializations for other types (boolean, and String)

    @Specialization
    public Object print(Object value) {
        doPrint(value);
        return value;
    }

    @TruffleBoundary
    private static void doPrint(Object value) {
        out.print(value);
    }
}

The superclass of all nodes (AstElement) has the methods executeGeneric(VirtaulFrame) and executeNumber, executeBoolean, executeChar and executeString. So the class PrintFunction also has these methods

So, what do you think is really causing the error message, or at least, what does it mean ?

I am taking inspiration from the Mumbler Language and SimpleLanguage both implemented with Truffle.

Answer 1

An answer I got from a great person on the Graal Slack

The value needs to come from somewhere. And Truffle expects you to have a form of expression as a subnode to your print function. The standard way is to add something like @NodeChild(value = "receiver", type = ExpressionNode.class) to the class definition Stefan Marr il y a 10 minutes if the value is not supposed to come from a subnode, i.e., child node, you can instead define an abstract execute(Object value) method, which the DLS will implement for you using the specializations