traverser.ts

// Recursively visit every node in sourcefile.
const visitSourceFile = (sourceFile: ts.SourceFile, context: ts.TransformationContext): ts.SourceFile => {
    const imports = new Set<RxJSPart>();

    const visitNodes = (node: ts.Node): ts.Node => {
        const [dispatchedNode, classification] = dispatch(node);
        imports.add(classification);

        return ts.visitEachChild(dispatchedNode, visitNodes, context);
    };

    const root = visitNodes(sourceFile) as ts.SourceFile;
    return addImports(root, imports)
};