Step 18 (part 3): Expand parser — expressions, commands, features

Tokenizer:
  * and % now emit as operators (were silently swallowed)
  Added keywords: install, measure, behavior, called
  5 new arithmetic operator tests

Parser — expression layer:
  Arithmetic (+, -, *, /, %) via parse-arith
  Unary not, no, unary minus
  the X of Y possessive (parse-the-expr)
  as Type conversion, X in Y membership, array literals [...]
  fetch URL parsing fixed — no longer consumes "as" meant for fetch

Parser — 8 new commands:
  return, throw, append...to, tell...end, for...in...end,
  make a Type, install Behavior, measure

Parser — 2 new features:
  def name(params)...end, behavior Name(params)...end

Parser — enhanced:
  wait for event [from target], on every event modifier

33 new parser tests (16 suites), 5 tokenizer tests.
3043/3043 full build, zero regressions.

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

spec/tests/test-hyperscript-parser.sx

@@ -375,6 +375,291 @@
       (assert= "hello" (nth ast 2)))))
 
 ;; ── Full expressions (matching tokenizer conformance) ─────────────
+(defsuite
+  "hs-parse-arithmetic"
+  (deftest
+    "addition"
+    (let
+      ((ast (hs-compile "set x to 1 + 2")))
+      (let
+        ((val (nth ast 2)))
+        (assert= (quote +) (first val))
+        (assert= 1 (nth val 1))
+        (assert= 2 (nth val 2)))))
+  (deftest
+    "subtraction"
+    (let
+      ((ast (hs-compile "set x to 10 - 3")))
+      (let
+        ((val (nth ast 2)))
+        (assert= (quote -) (first val))
+        (assert= 10 (nth val 1))
+        (assert= 3 (nth val 2)))))
+  (deftest
+    "multiplication"
+    (let
+      ((ast (hs-compile "set x to 4 * 5")))
+      (let
+        ((val (nth ast 2)))
+        (assert= (quote *) (first val))
+        (assert= 4 (nth val 1))
+        (assert= 5 (nth val 2)))))
+  (deftest
+    "division"
+    (let
+      ((ast (hs-compile "set x to 10 / 2")))
+      (let
+        ((val (nth ast 2)))
+        (assert= (quote /) (first val))
+        (assert= 10 (nth val 1))
+        (assert= 2 (nth val 2)))))
+  (deftest
+    "chained arithmetic"
+    (let
+      ((ast (hs-compile "set x to 1 + 2 + 3")))
+      (let
+        ((val (nth ast 2)))
+        (assert= (quote +) (first val))
+        (assert= 3 (nth val 2))))))
+
+(defsuite
+  "hs-parse-unary"
+  (deftest
+    "not expr"
+    (let
+      ((ast (hs-compile "if not x end")))
+      (let ((cnd (nth ast 1))) (assert= (quote not) (first cnd)))))
+  (deftest
+    "no expr"
+    (let
+      ((ast (hs-compile "if no x end")))
+      (let ((cnd (nth ast 1))) (assert= (quote no) (first cnd)))))
+  (deftest
+    "unary minus"
+    (let
+      ((ast (hs-compile "set x to -5")))
+      (let
+        ((val (nth ast 2)))
+        (assert= (quote -) (first val))
+        (assert= 0 (nth val 1))
+        (assert= 5 (nth val 2))))))
+
+(defsuite
+  "hs-parse-the-of"
+  (deftest
+    "the innerHTML of me"
+    (let
+      ((ast (hs-compile "set the innerHTML of me to 'hi'")))
+      (let
+        ((tgt (nth ast 1)))
+        (assert= (make-symbol ".") (first tgt))
+        (assert= "innerHTML" (nth tgt 2)))))
+  (deftest
+    "the as article skip"
+    (let
+      ((ast (hs-compile "set the result to 5")))
+      (let ((tgt (nth ast 1))) (assert= (quote it) (first tgt))))))
+
+(defsuite
+  "hs-parse-as-conversion"
+  (deftest
+    "expr as Int"
+    (let
+      ((ast (hs-compile "set x to y as Int")))
+      (let
+        ((val (nth ast 2)))
+        (assert= (quote as) (first val))
+        (assert= "Int" (nth val 2)))))
+  (deftest
+    "expr as String"
+    (let
+      ((ast (hs-compile "set x to count as String")))
+      (let
+        ((val (nth ast 2)))
+        (assert= (quote as) (first val))
+        (assert= "String" (nth val 2))))))
+
+(defsuite
+  "hs-parse-in-operator"
+  (deftest
+    "x in collection"
+    (let
+      ((ast (hs-compile "if x in items end")))
+      (let ((cnd (nth ast 1))) (assert= (quote in?) (first cnd))))))
+
+(defsuite
+  "hs-parse-array-literals"
+  (deftest
+    "empty array"
+    (let
+      ((ast (hs-compile "set x to []")))
+      (let
+        ((val (nth ast 2)))
+        (assert= (quote array) (first val))
+        (assert= 1 (len val)))))
+  (deftest
+    "array with elements"
+    (let
+      ((ast (hs-compile "set x to [1, 2, 3]")))
+      (let
+        ((val (nth ast 2)))
+        (assert= (quote array) (first val))
+        (assert= 4 (len val))
+        (assert= 1 (nth val 1))
+        (assert= 2 (nth val 2))
+        (assert= 3 (nth val 3))))))
+
+(defsuite
+  "hs-parse-return-throw"
+  (deftest
+    "return expr"
+    (let
+      ((ast (hs-compile "return 42")))
+      (assert= (quote return) (first ast))
+      (assert= 42 (nth ast 1))))
+  (deftest
+    "return bare"
+    (let
+      ((ast (hs-compile "return")))
+      (assert= (quote return) (first ast))
+      (assert= nil (nth ast 1))))
+  (deftest
+    "throw expr"
+    (let
+      ((ast (hs-compile "throw 'error'")))
+      (assert= (quote throw) (first ast))
+      (assert= "error" (nth ast 1)))))
+
+(defsuite
+  "hs-parse-append"
+  (deftest
+    "append to target"
+    (let
+      ((ast (hs-compile "append 'hello' to me")))
+      (assert= (quote append!) (first ast))
+      (assert= "hello" (nth ast 1))
+      (assert= (quote me) (first (nth ast 2))))))
+
+(defsuite
+  "hs-parse-tell"
+  (deftest
+    "tell target commands end"
+    (let
+      ((ast (hs-compile "tell <div/> add .active end")))
+      (assert= (quote tell) (first ast))
+      (assert= (quote query) (first (nth ast 1)))
+      (assert= (quote add-class) (first (nth ast 2))))))
+
+(defsuite
+  "hs-parse-for"
+  (deftest
+    "for x in items end"
+    (let
+      ((ast (hs-compile "for item in items log item end")))
+      (assert= (quote for) (first ast))
+      (assert= "item" (nth ast 1))
+      (assert= (quote ref) (first (nth ast 2)))
+      (assert= (quote log) (first (nth ast 3)))))
+  (deftest
+    "for with index"
+    (let
+      ((ast (hs-compile "for item in items index i log item end")))
+      (assert= (quote for) (first ast))
+      (assert= "item" (nth ast 1)))))
+
+(defsuite
+  "hs-parse-make"
+  (deftest
+    "make a Object"
+    (let
+      ((ast (hs-compile "make a Object")))
+      (assert= (quote make) (first ast))
+      (assert= "Object" (nth ast 1))))
+  (deftest
+    "make a Set called s"
+    (let
+      ((ast (hs-compile "make a Set called s")))
+      (assert= (quote make) (first ast))
+      (assert= "Set" (nth ast 1))
+      (assert= "s" (nth ast 2)))))
+
+(defsuite
+  "hs-parse-install"
+  (deftest
+    "install behavior"
+    (let
+      ((ast (hs-compile "install Draggable")))
+      (assert= (quote install) (first ast))
+      (assert= "Draggable" (nth ast 1))))
+  (deftest
+    "install with args"
+    (let
+      ((ast (hs-compile "install Sortable(true)")))
+      (assert= (quote install) (first ast))
+      (assert= "Sortable" (nth ast 1))
+      (assert= true (nth ast 2)))))
+
+(defsuite
+  "hs-parse-measure"
+  (deftest
+    "measure target"
+    (let
+      ((ast (hs-compile "measure me")))
+      (assert= (quote measure) (first ast))
+      (assert= (quote me) (first (nth ast 1))))))
+
+(defsuite
+  "hs-parse-wait-for"
+  (deftest
+    "wait for transitionend"
+    (let
+      ((ast (hs-compile "wait for transitionend")))
+      (assert= (quote wait-for) (first ast))
+      (assert= "transitionend" (nth ast 1))))
+  (deftest
+    "wait for click from target"
+    (let
+      ((ast (hs-compile "wait for click from #btn")))
+      (assert= (quote wait-for) (first ast))
+      (assert= "click" (nth ast 1))
+      (assert= :from (nth ast 2)))))
+
+(defsuite
+  "hs-parse-def-behavior"
+  (deftest
+    "def function"
+    (let
+      ((ast (hs-compile "def greet(name) log name end")))
+      (assert= (quote def) (first ast))
+      (assert= "greet" (nth ast 1))
+      (assert= 1 (len (nth ast 2)))
+      (assert= (quote log) (first (nth ast 3)))))
+  (deftest
+    "behavior with on handler"
+    (let
+      ((ast (hs-compile "behavior Clickable on click add .clicked end end")))
+      (assert= (quote behavior) (first ast))
+      (assert= "Clickable" (nth ast 1))
+      (assert= 1 (len (nth ast 3)))))
+  (deftest
+    "def no params"
+    (let
+      ((ast (hs-compile "def reset() set x to 0 end")))
+      (assert= (quote def) (first ast))
+      (assert= "reset" (nth ast 1))
+      (assert= 0 (len (nth ast 2))))))
+
+(defsuite
+  "hs-parse-every-modifier"
+  (deftest
+    "on every click"
+    (let
+      ((ast (hs-compile "on every click add .pulse end")))
+      (assert= (quote on) (first ast))
+      (assert= "click" (nth ast 1))
+      (assert= :every (nth ast 2))
+      (assert= true (nth ast 3)))))
+
 (defsuite
   "hs-parse-conformance"
   (deftest