Robuuster returns in javascript.

main.rkt

@@ -1439,32 +1439,13 @@ if (~a !== false) return ~a;" tmp (compile-expr arg) tmp tmp)))
       [(list f args ...) (compile-call f args)]
       [_ (literal->js d)]))
 
-  (define (top-tail-returnable? d)
-    (match d
-      [(list 'define _ ...) #f]
-      [(list 'define-values _ ...) #f]
-      [(list 'define-class _ ...) #f]
-      [(list 'set! _ ...) #f]
-      [(list 'vector-set! _ ...) #f]
-      [(list 'set-prop! _ ...) #f]
-      [(list 'delete-prop! _ ...) #f]
-      [(list 'while _ ...) #f]
-      [(list 'for _ ...) #f]
-      ;; Top-level js is statement/program output.  with-handlers may contain
-      ;; a handler used only for side effects; compiling it as an implicit
-      ;; tail return would emit return statements inside the generated
-      ;; try/catch and prematurely leave the caller's wrapper.  Use
-      ;; js/expression when the value of with-handlers is needed.
-      [(list 'with-handlers _ ...) #f]
-      [_ #t]))
-
   (define (compile-top forms)
-    (cond
-      [(null? forms) ""]
-      [(top-tail-returnable? (last forms))
-       (compile-body forms #:return-last? #t)]
-      [else
-       (compile-body forms #:return-last? #f)])))
+    ;; A js form produces JavaScript program/statement text.  It must be valid
+    ;; when handed directly to a WebView run/evaluateJavaScript entry point, so
+    ;; it may not invent top-level return statements.  Return insertion still
+    ;; happens in expression contexts and function bodies, where JavaScript
+    ;; return is syntactically valid.
+    (compile-body forms #:return-last? #f)))
 
 (define-syntax (js stx)
   (syntax-case stx ()