sucrase/dist/src/transformers/FlowTransformer.mjs

Super-fast alternative to Babel for when you can target modern JS runtimes

import Transformer from "./Transformer";
export default class FlowTransformer extends Transformer {
    constructor(rootTransformer, tokens) {
        super();
        this.rootTransformer = rootTransformer;
        this.tokens = tokens;
    }
    process() {
        // We need to handle all classes specially in order to remove `implements`.
        if (this.tokens.matchesKeyword("class")) {
            this.rootTransformer.processClass();
            return true;
        }
        return this.rootTransformer.processPossibleTypeRange();
    }
}