\newcommand{\foo}[1]{\bar{#1}} \renewcommand{\bar}[1]{\foo{#1}} % mutual recursion \foo{x} \def\x{\y}\def\y{z}\x % chained expansion

+>

#set page(paper: "a4") #set heading(numbering: "1.") #set math.equation(numbering: "(1)") /* \foo / / \y /

\foo{x} → \bar{x} → \foo{x} → ∞ Expected: hit depth limit, emit warning, output either x or the unexpanded \foo{x} Actual: / \foo */ — silently converted to a comment, lost the argument x entirely