From 0d52aedbd9ecc04c0540ad7d7d7ff2b5051dcaa5 Mon Sep 17 00:00:00 2001
From: Adam Chlipala <adam@chlipala.net>
Date: Tue, 19 Oct 2010 10:13:24 -0400
Subject: Smarter handling of unification variables for 'kindof' on projections

---
 src/elab.sml      |  2 +-
 src/elaborate.sml | 19 +++++++++++++++++++
 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/src/elab.sml b/src/elab.sml
index 97acec31..c042d916 100644
--- a/src/elab.sml
+++ b/src/elab.sml
@@ -1,4 +1,4 @@
-(* Copyright (c) 2008, Adam Chlipala
+(* Copyright (c) 2008-2010, Adam Chlipala
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
diff --git a/src/elaborate.sml b/src/elaborate.sml
index dcae4650..3346fc37 100644
--- a/src/elaborate.sml
+++ b/src/elaborate.sml
@@ -583,6 +583,25 @@
        | L'.CProj (c, n) =>
          (case hnormKind (kindof env c) of
               (L'.KTuple ks, _) => List.nth (ks, n - 1)
+            | (L'.KUnif (_, _, r), _) =>
+              let
+                  val ku = kunif loc
+                  val k = (L'.KTupleUnif (loc, [(n, ku)], ref NONE), loc)
+              in
+                  r := SOME k;
+                  k
+              end
+            | (L'.KTupleUnif (_, nks, r), _) =>
+              (case ListUtil.search (fn (n', k) => if n' = n then SOME k else NONE) nks of
+                   SOME k => k
+                 | NONE =>
+                   let
+                       val ku = kunif loc
+                       val k = (L'.KTupleUnif (loc, ((n, ku) :: nks), ref NONE), loc)
+                   in
+                       r := SOME k;
+                       k
+                   end)
             | k => raise CUnify' (CKindof (k, c, "tuple")))
 
        | L'.CError => kerror
-- 
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