From 11315d91cc33cf0d05a4d0359c9976fa190fef9d Mon Sep 17 00:00:00 2001
From: giles <giles.bradshaw@rose-ash.com>
Date: Sat, 25 Apr 2026 12:18:42 +0000
Subject: [PATCH] =?UTF-8?q?js-on-sx:=20var=20hoisting=20=E2=80=94=20hoist?=
 =?UTF-8?q?=20var=20names=20as=20undefined=20before=20funcdecls?=
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---
 lib/js/test.sh      | 14 +++++++++++++
 lib/js/transpile.sx | 51 ++++++++++++++++++++++++++++++++++++++++++---
 2 files changed, 62 insertions(+), 3 deletions(-)

diff --git a/lib/js/test.sh b/lib/js/test.sh
index 751da07b..9080735e 100755
--- a/lib/js/test.sh
+++ b/lib/js/test.sh
@@ -1333,6 +1333,15 @@ cat > "$TMPFILE" << 'EPOCHS'
 (epoch 4203)
 (eval "(let ((toks (js-tokenize \"a b\"))) (get (nth toks 1) :nl))")
 
+(epoch 4300)
+(eval "(js-eval \"var x = 5; x\")")
+(epoch 4301)
+(eval "(js-eval \"function f() { return x; var x = 42; } f()\")")
+(epoch 4302)
+(eval "(js-eval \"function f() { var y = 7; return y; } f()\")")
+(epoch 4303)
+(eval "(js-eval \"function f() { var z; z = 3; return z; } f()\")")
+
 EPOCHS
 
 
@@ -2058,6 +2067,11 @@ check 4201 "return+space+val → val"        '42'
 check 4202 "nl-before flag set after newline" 'true'
 check 4203 "nl-before flag false on same line" 'false'
 
+check 4300 "var decl program-level"         '5'
+check 4301 "var hoisted before use → undef" '"js-undefined"'
+check 4302 "var in function body"           '7'
+check 4303 "var then set in function"       '3'
+
 TOTAL=$((PASS + FAIL))
 if [ $FAIL -eq 0 ]; then
   echo "✓ $PASS/$TOTAL JS-on-SX tests passed"
diff --git a/lib/js/transpile.sx b/lib/js/transpile.sx
index 619d796f..69c6c4e3 100644
--- a/lib/js/transpile.sx
+++ b/lib/js/transpile.sx
@@ -486,6 +486,51 @@
                 (append inits (list (js-transpile body))))))))
       (list (js-sym "fn") param-syms body-tr))))
 
+(define
+  js-collect-var-decl-names
+  (fn
+    (decls)
+    (cond
+      ((empty? decls) (list))
+      ((js-tag? (first decls) "js-vardecl")
+        (cons
+          (nth (first decls) 1)
+          (js-collect-var-decl-names (rest decls))))
+      (else (js-collect-var-decl-names (rest decls))))))
+
+(define
+  js-collect-var-names
+  (fn
+    (stmts)
+    (cond
+      ((empty? stmts) (list))
+      ((and (list? (first stmts)) (js-tag? (first stmts) "js-var") (= (nth (first stmts) 1) "var"))
+        (append
+          (js-collect-var-decl-names (nth (first stmts) 2))
+          (js-collect-var-names (rest stmts))))
+      (else (js-collect-var-names (rest stmts))))))
+
+(define
+  js-dedup-names
+  (fn
+    (names seen)
+    (cond
+      ((empty? names) (list))
+      ((some (fn (s) (= s (first names))) seen)
+        (js-dedup-names (rest names) seen))
+      (else
+        (cons
+          (first names)
+          (js-dedup-names (rest names) (cons (first names) seen)))))))
+
+(define
+  js-var-hoist-forms
+  (fn
+    (names)
+    (map
+      (fn (name) (list (js-sym "define") (js-sym name) :js-undefined))
+      names)))
+
 (define
   js-transpile-tpl
   (fn
@@ -876,7 +921,7 @@
   (fn
     (stmts)
     (let
-      ((hoisted (js-collect-funcdecls stmts)))
+      ((hoisted (append (js-var-hoist-forms (js-dedup-names (js-collect-var-names stmts) (list))) (js-collect-funcdecls stmts))))
       (let
         ((rest-stmts (js-transpile-stmt-list stmts)))
         (cons (js-sym "begin") (append hoisted rest-stmts))))))
@@ -1297,7 +1342,7 @@
           (if
             (and (list? body) (js-tag? body "js-block"))
             (let
-              ((hoisted (js-collect-funcdecls (nth body 1))))
+              ((hoisted (append (js-var-hoist-forms (js-dedup-names (js-collect-var-names (nth body 1)) (list))) (js-collect-funcdecls (nth body 1)))))
               (append hoisted (js-transpile-stmt-list (nth body 1))))
             (list (js-transpile body)))))
       (list
@@ -1333,7 +1378,7 @@
           (if
             (and (list? body) (js-tag? body "js-block"))
             (let
-              ((hoisted (js-collect-funcdecls (nth body 1))))
+              ((hoisted (append (js-var-hoist-forms (js-dedup-names (js-collect-var-names (nth body 1)) (list))) (js-collect-funcdecls (nth body 1)))))
               (append hoisted (js-transpile-stmt-list (nth body 1))))
             (list (js-transpile body)))))
       (list