cl: block + return-from — 13 new tests (140 eval, 312 total green)

Sentinel propagation in cl-eval-body; cl-eval-block catches matching
sentinels; BLOCK/RETURN-FROM/RETURN dispatch added to cl-eval-list.
Parser: CL strings now {:cl-type "string"} dicts for proper CL semantics.

lib/common-lisp/eval.sx

@@ -37,15 +37,19 @@
 
 ;; ── body evaluation ───────────────────────────────────────────────
 
+(define cl-block-return?
+  (fn (v) (and (dict? v) (= (get v "cl-type") "block-return"))))
+
 (define cl-eval-body
   (fn (forms env)
     (cond
       ((= (len forms) 0) nil)
       ((= (len forms) 1) (cl-eval (nth forms 0) env))
       (:else
-        (do
-          (cl-eval (nth forms 0) env)
-          (cl-eval-body (rest forms) env))))))
+        (let ((result (cl-eval (nth forms 0) env)))
+          (if (cl-block-return? result)
+            result
+            (cl-eval-body (rest forms) env)))))))
 
 ;; ── lambda-list binding helpers ───────────────────────────────────
 
@@ -266,6 +270,24 @@
       {:cl-type "function" :builtin-fn (get cl-builtins name)}))
   (keys cl-builtins))
 
+;; ── BLOCK / RETURN-FROM ───────────────────────────────────────────
+
+(define cl-eval-block
+  (fn (args env)
+    (let ((name (nth args 0))
+          (body (rest args)))
+      (let ((result (cl-eval-body body env)))
+        (if (and (cl-block-return? result)
+                 (= (get result "name") name))
+          (get result "value")
+          result)))))
+
+(define cl-eval-return-from
+  (fn (args env)
+    (let ((name (nth args 0))
+          (val  (if (> (len args) 1) (cl-eval (nth args 1) env) nil)))
+      {:cl-type "block-return" :name name :value val})))
+
 ;; ── special form evaluators ───────────────────────────────────────
 
 (define cl-eval-if
@@ -541,6 +563,11 @@
           ((= head "LOCALLY")      (cl-eval-body args env))
           ((= head "EVAL-WHEN")    (cl-eval-eval-when args env))
           ((= head "DEFUN")        (cl-eval-defun args env))
+          ((= head "BLOCK")        (cl-eval-block args env))
+          ((= head "RETURN-FROM")  (cl-eval-return-from args env))
+          ((= head "RETURN")
+            (let ((val (if (> (len args) 0) (cl-eval (nth args 0) env) nil)))
+              {:cl-type "block-return" :name nil :value val}))
           ((= head "DEFVAR")       (cl-eval-defvar args env false))
           ((= head "DEFPARAMETER") (cl-eval-defvar args env true))
           ((= head "DEFCONSTANT")  (cl-eval-defvar args env true))