The alternative is to write these calls explicitly:

let somePrinter: Printer | undefined;
function createSomePrinter(): Printer {
	return somePrinter ??= createPrinter();
}

I did scan the repo and there was only one other top level memoize usage in services, on which @__PURE__ does nothing.

Did you validate locally that this is smaller?

I did, yep:

$ git diff --diff-filter=AM --no-index ./built/local-old/typingsInstaller.js ./built/local/typingsInstaller.js --numstat
1   5648    ./built/{local-old => local}/typingsInstaller.js

Its interesting that this is not tree shaked out ? i thought you said things are getting removed if not used. I dont see why typingInstaller needs printer. But thats a separate question i guess..

It's not tree shaken because the arrow function (which references createPrinter) is passed to another function (memoize), and it doesn't know that memorize doesn't immediately call the function or something. So it can't eliminate the memoize call because it could have a side effect.

I would absolutely love a way to mark certain functions themselves as side-effect free, but that doesn't seem to be a thing that bundlers support (they all seem to do it at the function call site instead, which is a shame).