Step 18 (part 7): Extensions — render components + SX escape

Two hyperscript extensions beyond stock:

render ~component :key val [into|before|after target]
  Tokenizer: ~ + ident → component token type
  Parser: render command with kwargs and optional position
  Compiler: emits (render-to-html ~comp :key val) or
            (hs-put! (render-to-html ...) pos target)
  Bridges hyperscript flow to SX component rendering

eval (sx-expression) — SX escape hatch
  Inside eval (...), content is SX syntax (not hyperscript)
  Parser: collect-sx-source extracts balanced parens from raw source
  Compiler: sx-parse at compile time, inlines AST directly
  Result: SX runs in handler scope — hyperscript variables visible!
  Also supports string form: eval '(+ 1 2)' for backward compat

  set name to "Giles"
  set greeting to eval (str "Hello " name)  -- name is visible!

16 new tests (parser + compiler + integration).
3127/3127 full build, zero regressions.

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

lib/hyperscript/parser.sx

@@ -7,7 +7,7 @@
 (define
   hs-parse
   (fn
-    (tokens)
+    (tokens src)
     (let
       ((p 0) (tok-len (len tokens)))
       (define tp (fn () (if (< p tok-len) (nth tokens p) nil)))
@@ -116,6 +116,13 @@
                 (do (adv!) (list (quote not) (parse-expr))))
               ((and (= typ "keyword") (= val "no"))
                 (do (adv!) (list (quote no) (parse-expr))))
+              ((and (= typ "keyword") (= val "eval"))
+                (do
+                  (adv!)
+                  (if
+                    (= (tp-type) "paren-open")
+                    (list (quote sx-eval) (collect-sx-source))
+                    (list (quote sx-eval) (parse-expr)))))
               ((and (= typ "keyword") (= val "the"))
                 (do (adv!) (parse-the-expr)))
               ((and (= typ "keyword") (= val "me"))
@@ -170,6 +177,8 @@
                   (let
                     ((operand (parse-atom)))
                     (list (quote -) 0 operand))))
+              ((= typ "component")
+                (do (adv!) (list (quote component) val)))
               (true nil)))))
       (define
         parse-poss
@@ -702,7 +711,68 @@
                 (let
                   ((body (parse-feat-body)))
                   (match-kw "end")
-                  (list (quote behavior) name params body)))))))
+                  (list (quote behavior) name params body))))))
+        (define
+          parse-render-kwargs
+          (fn
+            ()
+            (define
+              collect-kw
+              (fn
+                (acc)
+                (if
+                  (= (tp-type) "local")
+                  (let
+                    ((key (tp-val)))
+                    (adv!)
+                    (let
+                      ((val (parse-expr)))
+                      (collect-kw (append acc (list key val)))))
+                  acc)))
+            (collect-kw (list))))
+        (define
+          parse-render-cmd
+          (fn
+            ()
+            (let
+              ((comp (cond ((= (tp-type) "component") (let ((name (tp-val))) (adv!) name)) ((= (tp-type) "paren-open") (do (adv!) (let ((expr (parse-expr))) (if (= (tp-type) "paren-close") (adv!) nil) expr))) (true (let ((name (tp-val))) (adv!) name)))))
+              (let
+                ((kwargs (parse-render-kwargs)))
+                (let
+                  ((pos (cond ((match-kw "into") "into") ((match-kw "before") "before") ((match-kw "after") "after") (true nil))))
+                  (let
+                    ((target (if pos (parse-expr) nil)))
+                    (if
+                      pos
+                      (list (quote render) comp kwargs pos target)
+                      (list (quote render) comp kwargs))))))))
+        (define
+          collect-sx-source
+          (fn
+            ()
+            (let
+              ((start-pos (get (tp) "pos")))
+              (adv!)
+              (define
+                skip-to-close
+                (fn
+                  (depth)
+                  (cond
+                    ((at-end?) start-pos)
+                    ((= (tp-type) "paren-open")
+                      (do (adv!) (skip-to-close (+ depth 1))))
+                    ((= (tp-type) "paren-close")
+                      (if
+                        (= depth 0)
+                        (let
+                          ((end-pos (+ (get (tp) "pos") 1)))
+                          (adv!)
+                          end-pos)
+                        (do (adv!) (skip-to-close (- depth 1)))))
+                    (true (do (adv!) (skip-to-close depth))))))
+              (let
+                ((end-pos (skip-to-close 0)))
+                (substring src start-pos end-pos))))))
       (define
         parse-cmd
         (fn
@@ -768,6 +838,8 @@
                 (do (adv!) (parse-install-cmd)))
               ((and (= typ "keyword") (= val "measure"))
                 (do (adv!) (parse-measure-cmd)))
+              ((and (= typ "keyword") (= val "render"))
+                (do (adv!) (parse-render-cmd)))
               (true (parse-expr))))))
       (define
         parse-cmd-list
@@ -853,4 +925,4 @@
           (cons (quote do) features))))))
 
 ;; ── Convenience: source string → AST ─────────────────────────────
-(define hs-compile (fn (src) (hs-parse (hs-tokenize src))))
+(define hs-compile (fn (src) (hs-parse (hs-tokenize src) src)))