Additional handling for `&` symbol in map destructuring for :keys/:syms/:strs could be a breaking change.

Question

Before 1.13.0-alpha1:

(let [{:keys [&]} {:& 1}] &)
;; => 1

After:

(let [{:keys [&]} {:& 1}] &)
Syntax error compiling at (REPL:1:1).
Unable to resolve symbol: & in this context

Answer 1

Yes, the intent here is to carve this out of being allowed so it is available for syntax purposes in destructuring. We did a fair amount of searching and do not see this being used anywhere.

We've updated the reference page at https://clojure.org/reference/reader#_symbols to explicitly note this.