Status: refused by design
;; is not FunctionalScript. const a = 1;; is valid JavaScript, and fjs compile refuses it by design: the demo below shows what it prints.
JavaScript reads a stray ; as an empty statement that does nothing. FunctionalScript has one terminator per statement, so ;; is an error rather than a statement, and a stray ; cannot hide a statement that was meant to be there (module structure).
The row st.empty of refused constructs registers the refusal, and module structure gives its reason.
const a = 1;;
export default a;
The demo on this page compiles sample.mjs, the module above, with this build's fjs compile, and shows the line it prints and the token it refuses. Below that it shows what JavaScript answers for the same module: 1.
Remove the extra ;, as alternative.f.js does:
const a = 1;
export default a;
It answers 1.
Today fjs compile prints unexpected token at the refused token. The demo proposes what it should print instead: the reason at the same token, what JavaScript does there, and the allowed spelling, the line alternative.f.js writes, as help. The page compiles the alternative too, so the suggestion is one the compiler accepts.