What I wrote would be a syntax error in TypeScript (no name for the argument, wrong arrow), not a function that returns array with one element; I used Haskell-ish notation instead of TypeScript's more verbose "(structure: MyStructure) => MyElement[]".

I thought it was clear enough that I was being informal and what I meant was clear, but that was admittedly probably a mistake. But to infer an implication from that that I'm "unwilling to learn new things" is a non sequitur and honestly kind of an unnecessarily dickish accusation.