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js-on-sx: object + array destructuring

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Parser: jp-parse-vardecl handles {a, b} obj pattern and [a, , c]
arr pattern (with hole support) in addition to plain idents.
Emits (js-vardecl-obj names rhs) and (js-vardecl-arr names rhs).

Transpile: js-vardecl-forms dispatches on tag. Destructures emit
(define __destruct__ rhs) then (define name (js-get-prop __destruct__
key-or-index)) for each pattern element. Array holes (nil) are skipped.

418/420 unit (+4), 148/148 slice unchanged.
This commit is contained in:
giles
2026-04-23 22:32:24 +00:00
parent dd6375af18
commit 15c310cdc1
4 changed files with 175 additions and 19 deletions
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108
lib/js/parser.sx
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@@ -781,20 +781,102 @@
jp-parse-vardecl
(fn
(st)
(let
((nm (get (jp-peek st) :value)))
(do
(if
(= (get (jp-peek st) :type) "ident")
(jp-advance! st)
(error
(str "Expected ident in var decl, got " (get (jp-peek st) :type))))
(if
(jp-at? st "op" "=")
(do
(cond
((jp-at? st "punct" "{")
(let
((pattern (jp-parse-obj-pattern st)))
(jp-expect! st "op" "=")
(list (quote js-vardecl-obj) pattern (jp-parse-assignment st))))
((jp-at? st "punct" "[")
(let
((pattern (jp-parse-arr-pattern st)))
(jp-expect! st "op" "=")
(list (quote js-vardecl-arr) pattern (jp-parse-assignment st))))
(else
(let
((nm (get (jp-peek st) :value)))
(if
(= (get (jp-peek st) :type) "ident")
(jp-advance! st)
(list (quote js-vardecl) nm (jp-parse-assignment st)))
(list (quote js-vardecl) nm (list (quote js-undef))))))))
(error
(str
"Expected ident in var decl, got "
(get (jp-peek st) :type))))
(if
(jp-at? st "op" "=")
(begin
(jp-advance! st)
(list (quote js-vardecl) nm (jp-parse-assignment st)))
(list (quote js-vardecl) nm (list (quote js-undef)))))))))
(define
jp-parse-obj-pattern
(fn
(st)
(jp-advance! st)
(let
((names (list)))
(jp-parse-obj-pattern-loop st names)
(jp-expect! st "punct" "}")
names)))
(define
jp-parse-obj-pattern-loop
(fn
(st names)
(cond
((jp-at? st "punct" "}") nil)
(else
(begin
(let
((nm (get (jp-peek st) :value)))
(if
(or
(= (get (jp-peek st) :type) "ident")
(= (get (jp-peek st) :type) "string"))
(jp-advance! st)
(error "expected ident in obj pattern"))
(append! names nm))
(cond
((jp-at? st "punct" ",")
(begin (jp-advance! st) (jp-parse-obj-pattern-loop st names)))
(else nil)))))))
(define
jp-parse-arr-pattern
(fn
(st)
(jp-advance! st)
(let
((names (list)))
(jp-parse-arr-pattern-loop st names)
(jp-expect! st "punct" "]")
names)))
(define
jp-parse-arr-pattern-loop
(fn
(st names)
(cond
((jp-at? st "punct" "]") nil)
((jp-at? st "punct" ",")
(begin
(append! names nil)
(jp-advance! st)
(jp-parse-arr-pattern-loop st names)))
(else
(begin
(let
((nm (get (jp-peek st) :value)))
(if
(= (get (jp-peek st) :type) "ident")
(jp-advance! st)
(error "expected ident in arr pattern"))
(append! names nm))
(cond
((jp-at? st "punct" ",")
(begin (jp-advance! st) (jp-parse-arr-pattern-loop st names)))
(else nil)))))))
(define
jp-parse-var-stmt