From 4137eb9e73d7e4b6d1aa2fe5cff52e81c9ba10da Mon Sep 17 00:00:00 2001
From: Vincent St-Amour <stamourv@racket-lang.org>
Date: Mon, 31 Dec 2012 17:26:44 -0500
Subject: [PATCH] Make let: annotations optional.

---
 .../succeed/let:-partial-annotations.rkt      |  9 ++++++
 collects/typed-racket/base-env/prims.rkt      | 28 +++++++++++++++----
 2 files changed, 31 insertions(+), 6 deletions(-)
 create mode 100644 collects/tests/typed-racket/succeed/let:-partial-annotations.rkt

diff --git a/collects/tests/typed-racket/succeed/let:-partial-annotations.rkt b/collects/tests/typed-racket/succeed/let:-partial-annotations.rkt
new file mode 100644
index 0000000000..8b402854ff
--- /dev/null
+++ b/collects/tests/typed-racket/succeed/let:-partial-annotations.rkt
@@ -0,0 +1,9 @@
+#lang typed/racket/base
+
+(: f : Integer -> (Listof Any))
+(define (f x)
+  (let: loop ([i : Integer 0] [l '()])
+        (if (> i x)
+            l
+            (loop (add1 i) (cons i l)))))
+(f 10)
diff --git a/collects/typed-racket/base-env/prims.rkt b/collects/typed-racket/base-env/prims.rkt
index 57c0a767e2..3a61b1f571 100644
--- a/collects/typed-racket/base-env/prims.rkt
+++ b/collects/typed-racket/base-env/prims.rkt
@@ -416,13 +416,29 @@ This file defines two sorts of primitives. All of them are provided into any mod
 
 (define-syntax (let: stx)
   (syntax-parse stx #:literals (:)
-    [(let: nm:id ~! : ret-ty (bs:annotated-binding ...) . body)
+    [(let: nm:id ~! ; named let:
+           (~and (~seq rest ...)
+                 (~seq (~optional (~seq : ret-ty))
+                       (bs:optionally-annotated-binding ...) body ...)))
      (quasisyntax/loc stx
-       (#,(quasisyntax/loc stx
-            (letrec: ([nm : (bs.ty ... -> ret-ty)
-                          #,(quasisyntax/loc stx
-                              (lambda (bs.ann-name ...) . #,(syntax/loc stx body)))])
-                     #,(quasisyntax/loc stx nm)))
+       (#,(syntax-parse #'(rest ...)
+            #:literals (:)
+            [(: ret-ty (bs:annotated-binding ...) . body)
+             (quasisyntax/loc stx
+               (letrec: ([nm : (bs.ty ... -> ret-ty)
+                             #,(quasisyntax/loc stx
+                                 (lambda (bs.ann-name ...) . #,(syntax/loc stx body)))])
+                        #,(quasisyntax/loc stx nm)))]
+            [(: ret-ty (bs:optionally-annotated-binding ...) . body)
+             (quasisyntax/loc stx
+               (letrec ([nm #,(quasisyntax/loc stx
+                                (lambda (bs.ann-name ...) . (ann #,(syntax/loc stx body) ret-ty)))])
+                 #,(quasisyntax/loc stx nm)))]
+            [((bs:optionally-annotated-binding ...) . body)
+             (quasisyntax/loc stx
+               (letrec ([nm #,(quasisyntax/loc stx
+                                (lambda (bs.ann-name ...) . #,(syntax/loc stx body)))])
+                 #,(quasisyntax/loc stx nm)))])
         bs.rhs ...))]
     [(let: . rest)
      (syntax/loc stx (let-internal: . rest))]))