src/describe.sml

   1 (* HCoop Domtool (http://hcoop.sourceforge.net/)
   2  * Copyright (c) 2006-2007, Adam Chlipala
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public License
   6  * as published by the Free Software Foundation; either version 2
   7  * of the License, or (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write to the Free Software
  16  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
  17  *)
  18
  19 (* Error message generation *)
  20
  21 structure Describe :> DESCRIBE = struct
  22
  23 open Ast Print
  24
  25 structure SM = StringMap
  26
  27 exception UnequalDomains
  28
  29 fun eqRecord f (r1, r2) =
  30     (SM.appi (fn (k, v1) =>
  31                  case SM.find (r2, k) of
  32                      NONE => raise UnequalDomains
  33                    | SOME v2 =>
  34                      if f (v1, v2) then
  35                          ()
  36                      else
  37                          raise UnequalDomains) r1;
  38      SM.appi (fn (k, v2) =>
  39                  case SM.find (r1, k) of
  40                      NONE => raise UnequalDomains
  41                    | SOME v1 =>
  42                      if f (v1, v2) then
  43                          ()
  44                      else
  45                          raise UnequalDomains) r2;
  46      true)
  47     handle UnequalDomains => false
  48
  49 fun eqPred ((p1, _), (p2, _)) =
  50     case (p1, p2) of
  51         (CRoot, CRoot) => true
  52       | (CConst s1, CConst s2) => s1 = s2
  53       | (CPrefix p1, CPrefix p2) => eqPred (p1, p2)
  54       | (CNot p1, CNot p2) => eqPred (p1, p2)
  55       | (CAnd (p1, q1), CAnd (p2, q2)) =>
  56         eqPred (p1, p2) andalso eqPred (q1, q2)
  57
  58       | _ => false
  59
  60 fun eqTy (t1All as (t1, _), t2All as (t2, _)) =
  61     case (t1, t2) of
  62         (TBase s1, TBase s2) => s1 = s2
  63       | (TList t1, TList t2) => eqTy (t1, t2)
  64       | (TArrow (d1, r1), TArrow (d2, r2)) =>
  65         eqTy (d1, d2) andalso eqTy (r1, r2)
  66
  67       | (TAction (p1, d1, r1), TAction (p2, d2, r2)) =>
  68         eqPred (p1, p2) andalso eqRecord eqTy (d1, d2)
  69         andalso eqRecord eqTy (r1, r2)
  70
  71       | (TNested (p1, q1), TNested (p2, q2)) =>
  72         eqPred (p1, p2) andalso eqTy (q1, q2)
  73
  74       | (TUnif (_, ref (SOME t1)), _) => eqTy (t1, t2All)
  75       | (_, TUnif (_, ref (SOME t2))) => eqTy (t1All, t2)
  76
  77       | (TUnif (_, r1), TUnif (_, r2)) => r1 = r2
  78
  79       | (TError, TError) => true
  80
  81       | _ => false
  82
  83 fun describe_unification_error t ue =
  84     case ue of
  85         UnifyPred (p1, p2) =>
  86         (print "Reason: Incompatible contexts.\n";
  87          preface ("Have:", p_pred p1);
  88          preface ("Need:", p_pred p2))
  89       | UnifyTyp (t1, t2) =>
  90         if eqTy (t, t1) then
  91             ()
  92         else
  93             (print "Reason: Incompatible types.\n";
  94              preface ("Have:", p_typ t1);
  95              preface ("Need:", p_typ t2))
  96       | UnifyOccurs (name, t') =>
  97         if eqTy (t, t') then
  98             ()
  99         else
 100             (print "Reason: Occurs check failed for ";
 101              print name;
 102              print " in:\n";
 103              output (p_typ t))
 104
 105 fun will_be_action (t, _) =
 106     case t of
 107         TArrow (_, t') => will_be_action t'
 108       | TAction _ => true
 109       | TNested _ => true
 110       | TUnif (_, ref (SOME t')) => will_be_action t'
 111       | _ => false
 112
 113 fun get_first_arg (t, _) =
 114     case t of
 115         TArrow (t', _) => t'
 116       | TUnif (_, ref (SOME t')) => get_first_arg t'
 117       | _ => raise Fail "get_first_arg failed!"
 118
 119 fun describe_type_error loc te =
 120     case te of
 121         WrongType (place, e, t1, t2, ueo) =>
 122         (ErrorMsg.error (SOME loc) (place ^ " has wrong type.");
 123          preface (" Expression:", p_exp e);
 124          preface ("Actual type:", p_typ t1);
 125          preface ("Needed type:", p_typ t2);
 126          Option.app (describe_unification_error t1) ueo)
 127       | WrongForm (place, form, e, t, ueo) =>
 128         if form = "action" andalso will_be_action t then
 129             (ErrorMsg.error (SOME loc) "Not enough arguments passed to configuration function.";
 130              preface (" Expression so far:", p_exp e);
 131              preface ("Next argument type:", p_typ (get_first_arg t)))
 132         else
 133             (ErrorMsg.error (SOME loc) (place ^ " has a non-" ^ form ^ " type.");
 134              preface ("Expression:", p_exp e);
 135              preface ("      Type:", p_typ t);
 136              Option.app (describe_unification_error t) ueo)
 137       | UnboundVariable name =>
 138         ErrorMsg.error (SOME loc) ("Unbound variable " ^ name ^ ".\n")
 139       | WrongPred (place, p1, p2) =>
 140         (ErrorMsg.error (SOME loc) ("Context incompatibility for " ^ place ^ ".");
 141          preface ("Have:", p_pred p1);
 142          preface ("Need:", p_pred p2))
 143
 144 end