--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/sigcheck.sml	Sat Jun 15 08:18:47 2013 -0400
@@ -0,0 +1,97 @@
+(* Copyright (c) 2013, Adam Chlipala
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * - Redistributions of source code must retain the above copyright notice,
+ *   this list of conditions and the following disclaimer.
+ * - Redistributions in binary form must reproduce the above copyright notice,
+ *   this list of conditions and the following disclaimer in the documentation
+ *   and/or other materials provided with the distribution.
+ * - The names of contributors may not be used to endorse or promote products
+ *   derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ *)
+
+structure SigCheck :> SIG_CHECK = struct
+
+open Mono
+
+structure IS = IntBinarySet
+structure E = ErrorMsg
+
+fun check (ds, sl) =
+    let
+        fun isSiggy siggers =
+            MonoUtil.Decl.exists {typ = fn _ => false,
+                                  decl = fn _ => false,
+                                  exp = fn e =>
+                                        case e of
+                                            ERel n => IS.member (siggers, n)
+                                          | EFfiApp ("Basis", "sigString", _) => true
+                                          | _ => false}
+
+        fun sigify' sigdecs e =
+            case e of
+                ENamed n => if IS.member (sigdecs, n) then
+                                (EApp ((e, E.dummySpan),
+                                       (ERecord [], E.dummySpan)))
+                            else
+                                e
+              | _ => e
+
+        fun sigify sigdecs =
+            MonoUtil.Decl.map {typ = fn x => x,
+                               decl = fn d => d,
+                               exp = sigify' sigdecs}
+
+        fun sigifyE sigdecs =
+            MonoUtil.Exp.map {typ = fn x => x,
+                              exp = sigify' sigdecs}
+
+        fun isFun (e, _) =
+            case e of
+                EAbs _ => true
+              | _ => false
+
+        fun doDecl (d : decl, (siggers, sigdecs)) =
+            case #1 d of
+                DVal (x, n, t, e, s) =>
+                if isSiggy siggers d then
+                    if isFun e then
+                        (sigify sigdecs d, (IS.add (siggers, n), sigdecs))
+                    else
+                        ((DVal (x, n, (TFun ((TRecord [], #2 d), t), #2 d),
+                                (EAbs ("_", (TRecord [], #2 d), t, sigifyE sigdecs e), #2 d),
+                                s), #2 d),
+                         (IS.add (siggers, n),
+                          IS.add (sigdecs, n)))
+                else
+                    (sigify sigdecs d, (siggers, sigdecs))
+              | DValRec vis =>
+                if isSiggy siggers d then
+                    (sigify sigdecs d,
+                     (foldl IS.add' siggers (map #2 vis),
+                      sigdecs))
+                else
+                    (sigify sigdecs d, (siggers, sigdecs))
+              | _ => (sigify sigdecs d, (siggers, sigdecs))
+
+        val (ds, _) = ListUtil.foldlMap doDecl (IS.empty, IS.empty) ds
+    in
+        (ds, sl)
+    end
+
+end