Fix: local bindings now shadow HTML tag special forms in browser evaluator

Root cause: sx_browser.ml registered all HTML tags (a, b, i, p, s, u, g, etc.)
as custom special forms. The evaluator's step_eval_list checked custom special
forms BEFORE checking local env bindings. So (let ((a (fn () 42))) (a))
matched the HTML tag <a> instead of calling the local function a.

Fix: skip custom special forms AND render-check when the symbol is bound in
the local env. Added (not (env-has? env name)) guard to both checks in
step-eval-list (spec/evaluator.sx and transpiled sx_ref.ml).

This was the root cause of "[sx] resume: Not callable: nil" — after hs-wait
resumed, calling letrec-bound functions like wait-boot (which is not an HTML
tag) worked, but any function whose name collided with an HTML tag failed.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

hosts/ocaml/browser/test_wasm.sh

@@ -299,6 +299,48 @@ node -e '
     K.eval("(let ((d (list))) (let ((el (with-island-scope (fn (x) (append! d x)) (fn () (render-to-dom (quote (div :class (deref test-reactive-sig) \"content\")) (global-env) nil))))) (reset! test-reactive-sig \"after\") (dom-get-attr el \"class\")))"),
     "after");
 
+  // =====================================================================
+  // Section 4: Letrec + perform resume (async _driveAsync)
+  // =====================================================================
+
+  // Define the letrec+perform pattern — this matches the test-runner island
+  K.eval("(define __letrec-test-fn (letrec ((other (fn () \"from-other\")) (go (fn () (do (perform {:op \"io-sleep\" :args (list 50)}) (other))))) go))");
+
+  // Get the function as a JS-callable value
+  var letrecFn = K.eval("__letrec-test-fn");
+  if (typeof letrecFn !== "function") {
+    fail++; console.error("FAIL: letrec-fn not callable, got: " + typeof letrecFn);
+  } else {
+    // Call via callFn — same path as island click handlers
+    var letrecResult = K.callFn(letrecFn, []);
+    // Resume through all suspensions — tests that resume() preserves letrec env
+    try {
+      while (letrecResult && letrecResult.suspended) { letrecResult = letrecResult.resume(null); }
+      assert("letrec sibling after perform resume", letrecResult, "from-other");
+    } catch(e) {
+      fail++; console.error("FAIL: letrec perform resume: " + (e.message || e));
+    }
+  }
+
+  // Recursive letrec after perform — the wait-boot pattern
+  K.eval("(define __wb-counter 0)");
+  K.eval("(define __recur-test-fn (letrec ((recur (fn () (set! __wb-counter (+ __wb-counter 1)) (if (>= __wb-counter 3) \"done\" (do (perform {:op \"io-sleep\" :args (list 10)}) (recur)))))) (fn () (set! __wb-counter 0) (recur))))");
+
+  var recurFn = K.eval("__recur-test-fn");
+  if (typeof recurFn !== "function") {
+    fail++; console.error("FAIL: recur-fn not callable, got: " + typeof recurFn);
+  } else {
+    var recurResult = K.callFn(recurFn, []);
+    try {
+      // Resume through all suspensions synchronously
+      while (recurResult && recurResult.suspended) { recurResult = recurResult.resume(null); }
+      assert("recursive letrec after perform", recurResult, "done");
+      assert("recursive letrec counter", K.eval("__wb-counter"), 3);
+    } catch(e) {
+      fail++; console.error("FAIL: recursive letrec perform: " + (e.message || e));
+    }
+  }
+
   // =====================================================================
   // Summary
   // =====================================================================

shared/static/wasm/sx/hs-integration.sxbc

@@ -1,3 +1,3 @@
 (sxbc 1 "99bd2816b1cd7891"
   (code
-    :constants ("hs-handler" {:upvalue-count 0 :arity 1 :constants ("hs-to-sx-from-source" "eval-expr-cek" "list" fn me let it event) :bytecode (20 0 0 16 0 48 1 17 1 20 1 0 1 3 0 1 4 0 52 2 0 1 1 5 0 1 6 0 2 52 2 0 2 1 7 0 2 52 2 0 2 52 2 0 2 16 1 52 2 0 3 52 2 0 3 49 1 50)} "hs-activate!" {:upvalue-count 0 :arity 1 :constants ("dom-get-attr" "_" "not" "dom-get-data" "hs-active" "dom-set-data" "hs-handler") :bytecode (20 0 0 16 0 1 1 0 48 2 17 1 16 1 6 33 15 0 5 20 3 0 16 0 1 4 0 48 2 52 2 0 1 33 30 0 20 5 0 16 0 1 4 0 3 48 3 5 20 6 0 16 1 48 1 17 2 16 2 16 0 49 1 32 1 0 2 50)} "hs-boot!" {:upvalue-count 0 :arity 0 :constants ("dom-query-all" "host-get" "host-global" "document" "body" "[_]" "for-each" {:upvalue-count 0 :arity 1 :constants ("hs-activate!") :bytecode (20 0 0 16 0 49 1 50)}) :bytecode (20 0 0 20 1 0 20 2 0 1 3 0 48 1 1 4 0 48 2 1 5 0 48 2 17 0 51 7 0 16 0 52 6 0 2 50)} "hs-boot-subtree!" {:upvalue-count 0 :arity 1 :constants ("dom-query-all" "[_]" "for-each" {:upvalue-count 0 :arity 1 :constants ("hs-activate!") :bytecode (20 0 0 16 0 49 1 50)} "dom-get-attr" "_" "hs-activate!") :bytecode (20 0 0 16 0 1 1 0 48 2 17 1 51 3 0 16 1 52 2 0 2 5 20 4 0 16 0 1 5 0 48 2 33 10 0 20 6 0 16 0 49 1 32 1 0 2 50)}) :bytecode (51 1 0 128 0 0 5 51 3 0 128 2 0 5 51 5 0 128 4 0 5 51 7 0 128 6 0 50)))
+    :constants ("hs-handler" {:upvalue-count 0 :arity 1 :constants ("hs-to-sx-from-source" "eval-expr-cek" "list" fn me let it event) :bytecode (20 0 0 16 0 48 1 17 1 20 1 0 1 3 0 1 4 0 52 2 0 1 1 5 0 1 6 0 2 52 2 0 2 1 7 0 2 52 2 0 2 52 2 0 2 16 1 52 2 0 3 52 2 0 3 49 1 50)} "hs-activate!" {:upvalue-count 0 :arity 1 :constants ("dom-get-attr" "_" "not" "dom-get-data" "hs-active" "dom-set-data" "hs-handler") :bytecode (20 0 0 16 0 1 1 0 48 2 17 1 16 1 6 33 15 0 5 20 3 0 16 0 1 4 0 48 2 52 2 0 1 33 30 0 20 5 0 16 0 1 4 0 3 48 3 5 20 6 0 16 1 48 1 17 2 16 2 16 0 49 1 32 1 0 2 50)} "hs-boot!" {:upvalue-count 0 :arity 0 :constants ("dom-query-all" "host-get" "host-global" "document" "body" "[_]" "for-each" {:upvalue-count 0 :arity 1 :constants ("hs-activate!") :bytecode (20 0 0 16 0 49 1 50)}) :bytecode (20 0 0 1 3 0 52 2 0 1 1 4 0 52 1 0 2 1 5 0 48 2 17 0 51 7 0 16 0 52 6 0 2 50)} "hs-boot-subtree!" {:upvalue-count 0 :arity 1 :constants ("dom-query-all" "[_]" "for-each" {:upvalue-count 0 :arity 1 :constants ("hs-activate!") :bytecode (20 0 0 16 0 49 1 50)} "dom-get-attr" "_" "hs-activate!") :bytecode (20 0 0 16 0 1 1 0 48 2 17 1 51 3 0 16 1 52 2 0 2 5 20 4 0 16 0 1 5 0 48 2 33 10 0 20 6 0 16 0 49 1 32 1 0 2 50)}) :bytecode (51 1 0 128 0 0 5 51 3 0 128 2 0 5 51 5 0 128 4 0 5 51 7 0 128 6 0 50)))

shared/static/wasm/sx/module-manifest.json

@@ -1006,6 +1006,7 @@
       "hs-last",
       "hs-repeat-times",
       "hs-repeat-forever",
+      "hs-repeat-while",
       "hs-fetch",
       "hs-coerce",
       "hs-add",

shared/static/wasm/sx_browser.bc.wasm.js

@@ -1792,7 +1792,7 @@
             blake2_js_for_wasm_create: blake2_js_for_wasm_create};
    }
    (globalThis))
-({"link":[["runtime-0db9b496",0],["prelude-d7e4b000",0],["stdlib-23ce0836",[]],["re-9a0de245",[2]],["sx-875d5bae",[2,3]],["jsoo_runtime-f96b44a8",[2]],["js_of_ocaml-651f6707",[2,5]],["dune__exe__Sx_browser-def18509",[2,4,6]],["std_exit-10fb8830",[2]],["start-f808dbe1",0]],"generated":(b=>{var
+({"link":[["runtime-0db9b496",0],["prelude-d7e4b000",0],["stdlib-23ce0836",[]],["re-9a0de245",[2]],["sx-624c0574",[2,3]],["jsoo_runtime-f96b44a8",[2]],["js_of_ocaml-651f6707",[2,5]],["dune__exe__Sx_browser-def18509",[2,4,6]],["std_exit-10fb8830",[2]],["start-f808dbe1",0]],"generated":(b=>{var
 c=b,a=b?.module?.export||b;return{"env":{"caml_ba_kind_of_typed_array":()=>{throw new
 Error("caml_ba_kind_of_typed_array not implemented")},"caml_exn_with_js_backtrace":()=>{throw new
 Error("caml_exn_with_js_backtrace not implemented")},"caml_int64_create_lo_mi_hi":()=>{throw new

spec/evaluator.sx

@@ -1820,7 +1820,9 @@
               ("define-syntax" (step-sf-define args env kont))
               (_
                 (cond
+                  (and
                     (has-key? *custom-special-forms* name)
+                    (not (env-has? env name)))
                   (make-cek-value
                     ((get *custom-special-forms* name) args env)
                     env
@@ -1829,7 +1831,10 @@
                   (let
                     ((mac (env-get env name)))
                     (make-cek-state (expand-macro mac args env) env kont))
-                  (and *render-check* (*render-check* expr env))
+                  (and
+                    *render-check*
+                    (not (env-has? env name))
+                    (*render-check* expr env))
                   (make-cek-value (*render-fn* expr env) env kont)
                   :else (step-eval-call head args env kont)))))
           (step-eval-call head args env kont))))))