

The infix syntax is not great, but you can at least write frac(n (n + 1), 2) and it renders the way you would expect.
Edit:
This is not even an option in typst, which uses the space as an escape character.
Technically LaTeX does this too with omitted curly braces:
\sum_{n=1}^9 % works
\sum_{n=1}^10 % doesn't work
Everyone just quickly learns to not do that.


That is basically what the EUPL is.