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js-on-sx: rest in array pattern + nested pattern tolerance

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Array destructure now supports [a, ...rest]. Rest entry is
transpiled to (define name (js-list-slice tmp i (len tmp))).

Nested patterns like [[a,b], c] now parse (as holes) instead of
erroring. jp-skip-balanced skips nested groups.

440/442 unit (+2), 148/148 slice unchanged.
This commit is contained in:
giles
2026-04-23 22:58:49 +00:00
parent 1459f7a637
commit c257971bb1
3 changed files with 72 additions and 0 deletions
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51
lib/js/parser.sx
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@@ -900,6 +900,29 @@
(append! names nil)
(jp-advance! st)
(jp-parse-arr-pattern-loop st names)))
((jp-at? st "punct" "...")
(begin
(jp-advance! st)
(when
(= (get (jp-peek st) :type) "ident")
(append! names (list "rest" (get (jp-peek st) :value)))
(jp-advance! st))))
((jp-at? st "punct" "[")
(begin
(jp-skip-balanced st "[" "]")
(append! names nil)
(cond
((jp-at? st "punct" ",")
(begin (jp-advance! st) (jp-parse-arr-pattern-loop st names)))
(else nil))))
((jp-at? st "punct" "{")
(begin
(jp-skip-balanced st "{" "}")
(append! names nil)
(cond
((jp-at? st "punct" ",")
(begin (jp-advance! st) (jp-parse-arr-pattern-loop st names)))
(else nil))))
(else
(begin
(let
@@ -909,11 +932,39 @@
(jp-advance! st)
(error "expected ident in arr pattern"))
(append! names nm))
(when
(jp-at? st "op" "=")
(begin (jp-advance! st) (jp-parse-assignment st)))
(cond
((jp-at? st "punct" ",")
(begin (jp-advance! st) (jp-parse-arr-pattern-loop st names)))
(else nil)))))))
(define
jp-skip-balanced
(fn
(st open close)
(jp-expect! st "punct" open)
(let ((depth 1)) (jp-skip-balanced-loop st open close depth))))
(define
jp-skip-balanced-loop
(fn
(st open close depth)
(cond
((<= depth 0) nil)
((>= (get st :idx) (len (get st :tokens))) nil)
((jp-at? st "punct" open)
(begin
(jp-advance! st)
(jp-skip-balanced-loop st open close (+ depth 1))))
((jp-at? st "punct" close)
(begin
(jp-advance! st)
(jp-skip-balanced-loop st open close (- depth 1))))
(else
(begin (jp-advance! st) (jp-skip-balanced-loop st open close depth))))))
(define
jp-parse-var-stmt
(fn