From 5470604b70b53010308d558299ba3668b7b8af17 Mon Sep 17 00:00:00 2001
From: Eric Dobson <eric.n.dobson@gmail.com>
Date: Wed, 21 May 2014 09:10:43 -0700
Subject: [PATCH] Make unfold use typecase instead of subst.

original commit: 42acb08399729acc20f6900b330bab9396f796d8
---
 .../typed-racket/types/substitute.rkt              | 14 +++++++-------
 .../typed-racket-lib/typed-racket/types/utils.rkt  |  8 +++++---
 2 files changed, 12 insertions(+), 10 deletions(-)

diff --git a/pkgs/typed-racket-pkgs/typed-racket-lib/typed-racket/types/substitute.rkt b/pkgs/typed-racket-pkgs/typed-racket-lib/typed-racket/types/substitute.rkt
index 7ab15034..49bfeb42 100644
--- a/pkgs/typed-racket-pkgs/typed-racket-lib/typed-racket/types/substitute.rkt
+++ b/pkgs/typed-racket-pkgs/typed-racket-lib/typed-racket/types/substitute.rkt
@@ -38,15 +38,15 @@
 ;; TODO: Figure out if free var checking/short circuiting is actually a performance improvement.
 
 ;; substitute-many : Hash[Name,Type] Type -> Type
-(define/cond-contract (substitute-many subst target #:Un [Un (lambda (args) (apply Un args))])
-  ((simple-substitution/c Type?) (#:Un procedure?) . ->* .  Type?)
-  (define (sb t) (substitute-many subst t #:Un Un))
+(define/cond-contract (substitute-many subst target)
+  (simple-substitution/c Type? . -> .  Type?)
+  (define (sb t) (substitute-many subst t))
   (define names (hash-keys subst))
   (define fvs (free-vars* target))
   (if (ormap (lambda (name) (free-vars-has-key? fvs name)) names)
       (type-case (#:Type sb #:Filter (sub-f sb) #:Object (sub-o sb))
                  target
-                 [#:Union tys (Un (map sb tys))]
+                 [#:Union tys (apply Un (map sb tys))]
                  [#:F name (hash-ref subst name target)]
                  [#:arr dom rng rest drest kws
                         (cond
@@ -81,9 +81,9 @@
 
 
 ;; substitute : Type Name Type -> Type
-(define/cond-contract (substitute image name target #:Un [Un (lambda (args) (apply Un args))])
-  ((Type/c symbol? Type?) (#:Un procedure?) . ->* . Type?)
-  (substitute-many (hash name image) target #:Un Un))
+(define/cond-contract (substitute image name target)
+  (Type/c symbol? Type? . -> . Type?)
+  (substitute-many (hash name image) target))
 
 ;; implements angle bracket substitution from the formalism
 ;; substitute-dots : Listof[Type] Option[type] Name Type -> Type
diff --git a/pkgs/typed-racket-pkgs/typed-racket-lib/typed-racket/types/utils.rkt b/pkgs/typed-racket-pkgs/typed-racket-lib/typed-racket/types/utils.rkt
index 875f035a..ce508eb0 100644
--- a/pkgs/typed-racket-pkgs/typed-racket-lib/typed-racket/types/utils.rkt
+++ b/pkgs/typed-racket-pkgs/typed-racket-lib/typed-racket/types/utils.rkt
@@ -19,9 +19,11 @@
 (define (unfold t)
   (match t
     [(Mu: name b)
-     (substitute t name b #:Un (lambda (tys)
-                                 (make-Union (sort tys < #:key Type-seq))))]
-    [_ (int-err "unfold: requires Mu type, got ~a" t)]))
+     (define (sb target)
+       (type-case (#:Type sb #:Filter (sub-f sb) #:Object (sub-o sb))
+         target
+         [#:F name* (if (eq? name name*) t target)]))
+     (sb b)]))
 
 (define (instantiate-poly t types)
   (match t