I have an antlr4 grammar with dozens of rules. There’s code I want to run as the Visitor enters each node, i.e. shared behaviour across all node types. For example, I might have a grammar like this…

lost : jack | kate;
jack : 'JACK';
kate : 'KATE';

…and a visitor like this (I’m using antlr4ts, so the generated code is in TypeScript)…

export default class MyVisitor extends VisitorInterface {
    sharedBehaviour(ctx: ParseNode) {
        // ...
    }
    visitLost(ctx: LostContext) {
         this.sharedBehaviour(ctx);
         // ...
    }
    visitJack(ctx: JackContext) {
         this.sharedBehaviour(ctx);
         // ...
    }
    visitKate(ctx: KateContext) {
         this.sharedBehaviour(ctx);
         // ...
    }
}

How can I replicate this without copy/pasting this.sharedBehaviour(ctx) into every single visitX method?

Based on the docs, I thought I could maybe define a custom superclass for all the parse nodes, and in the accept(...) method of my custom parse node, I could call visitor.sharedBehaviour(...). But I’m not sure how to add this sharedBehaviour(...) method to the antlr-generated visitor interface (which I called VisitorInterface above), so that it’s visible to the parse nodes. Also, I’d prefer to avoid messing with the code generation, and I thought there’d be an easier way to do this.