From 889f1591037d26fa6557bb637b8590ba2dad0d49 Mon Sep 17 00:00:00 2001
From: "J. Ian Johnson" <ianj@ccs.neu.edu>
Date: Wed, 28 Nov 2012 13:05:17 -0500
Subject: [PATCH] Singleton optimization for sequences that would allocate.

---
 collects/racket/private/for.rkt | 6 ++++--
 collects/racket/set.rkt         | 3 ++-
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/collects/racket/private/for.rkt b/collects/racket/private/for.rkt
index c5578ce67f..fc61570f90 100644
--- a/collects/racket/private/for.rkt
+++ b/collects/racket/private/for.rkt
@@ -1725,7 +1725,8 @@
   (define-sequence-syntax *in-list
     (lambda () #'in-list)
     (lambda (stx)
-      (syntax-case stx ()
+      (syntax-case stx (list)
+        [[(id) (_ (list expr))] #'[(id) (:do-in ([(id) expr]) #t () #t () #t #f ())]]
         [[(id) (_ lst-expr)]
          (for-clause-syntax-protect
           #'[(id)
@@ -1751,7 +1752,8 @@
   (define-sequence-syntax *in-mlist
     (lambda () #'in-mlist)
     (lambda (stx)
-      (syntax-case stx ()
+      (syntax-case stx (mlist)
+        [[(id) (_ (mlist expr))] #'[(id) (:do-in ([(id) expr]) #t () #t () #t #f ())]]
         [[(id) (_ lst-expr)]
          (for-clause-syntax-protect
           #'[(id)
diff --git a/collects/racket/set.rkt b/collects/racket/set.rkt
index 68c6845ad7..f79c39c8fe 100644
--- a/collects/racket/set.rkt
+++ b/collects/racket/set.rkt
@@ -308,7 +308,8 @@
 (define-sequence-syntax *in-set
   (lambda () #'in-set)
   (lambda (stx)
-    (syntax-case stx ()
+    (syntax-case stx (set)
+      [[(id) (_ (set expr))] #'[(id) (:do-in ([(id) expr]) #t () #t () #t #f ())]]
       [[(id) (_ st)]
        #`[(id)
           (:do-in