Permission revocation
[hcoop/domtool2.git] / src / tycheck.sml
index 5eca71e..007a0fe 100644 (file)
  * You should have received a copy of the GNU General Public License
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
-*)
+ *)
 
 (* Domtool configuration language type checking *)
 
 structure Tycheck :> TYCHECK = struct
 
-open Ast Print
+open Ast Print Env
 
 structure SM = StringMap
 
-type env = typ SM.map
-val empty = SM.empty
+val externFlag = ref false
+fun allowExterns () = externFlag := true
+fun disallowExterns () = externFlag := false
 
 local
     val unifCount = ref 0
@@ -90,6 +91,9 @@ fun eqTy (t1All as (t1, _), t2All as (t2, _)) =
        eqPred (p1, p2) andalso eqRecord eqTy (d1, d2)
        andalso eqRecord eqTy (r1, r2)
 
+      | (TNested (p1, q1), TNested (p2, q2)) =>
+       eqPred (p1, p2) andalso eqTy (q1, q2)
+
       | (TUnif (_, ref (SOME t1)), _) => eqTy (t1, t2All)
       | (_, TUnif (_, ref (SOME t2))) => eqTy (t1All, t2)
 
@@ -110,14 +114,12 @@ datatype type_error =
         WrongType of string * exp * typ * typ * unification_error option
        | WrongForm of string * string * exp * typ * unification_error option
        | UnboundVariable of string
-
-fun preface (s, d) = printd (PD.hovBox (PD.PPS.Rel 0,
-                                       [PD.string s, PD.space 1, d]))
+       | WrongPred of string * pred * pred
 
 fun describe_unification_error t ue =
     case ue of
        UnifyPred (p1, p2) =>
-       (print "Reason: Incompatible predicates.\n";
+       (print "Reason: Incompatible contexts.\n";
         preface ("Have:", p_pred p1);
         preface ("Need:", p_pred p2))
       | UnifyTyp (t1, t2) =>
@@ -151,32 +153,64 @@ fun describe_type_error loc te =
         Option.app (describe_unification_error t) ueo)
       | UnboundVariable name =>
        ErrorMsg.error (SOME loc) ("Unbound variable " ^ name ^ ".\n")
+      |        WrongPred (place, p1, p2) =>
+       (ErrorMsg.error (SOME loc) ("Context incompatibility for " ^ place ^ ".");
+        preface ("Have:", p_pred p1);
+        preface ("Need:", p_pred p2))
 
-fun unifyPred (p1All as (p1, _), p2All as (p2, _)) =
+fun predImplies (p1All as (p1, _), p2All as (p2, _)) =
     case (p1, p2) of
-       (CRoot, CRoot) => ()
-      | (CConst s1, CConst s2) =>
-       if s1 = s2 then
-           ()
-       else
-           raise (Unify (UnifyPred (p1All, p2All)))
-      | (CPrefix p1, CPrefix p2) => unifyPred (p1, p2)
-      | (CNot p1, CNot p2) => unifyPred (p1, p2)
-      | (CAnd (p1, q1), CAnd (p2, q2)) =>
-       (unifyPred (p1, p2);
-        unifyPred (q1, q2))
+       (_, CAnd (p1, p2)) => predImplies (p1All, p1) andalso predImplies (p1All, p2)
+      | (CAnd (p1, p2), _) => predImplies (p1, p2All) orelse predImplies (p2, p2All)
 
-      | _ => raise (Unify (UnifyPred (p1All, p2All)))
+      | (_, CPrefix (CRoot, _)) => true
+      | (CNot (CPrefix (CRoot, _), _), _) => true
 
-fun unifyRecord f (r1, r2) =
-    (SM.appi (fn (k, v1) =>
-                case SM.find (r2, k) of
-                    NONE => raise UnequalDomains
-                  | SOME v2 => f (v1, v2)) r1;
-     SM.appi (fn (k, v2) =>
-                case SM.find (r1, k) of
-                    NONE => raise UnequalDomains
-                  | SOME v1 => f (v1, v2)) r2)
+      | (CRoot, CRoot) => true
+
+      | (CConst s1, CConst s2) => s1 = s2
+
+      | (CPrefix p1, CPrefix p2) => predImplies (p1, p2)
+      | (_, CPrefix p2) => predImplies (p1All, p2)
+
+      | (CNot p1, CNot p2) => predImplies (p2, p1)
+      | (CRoot, CNot (CConst _, _)) => true
+      | (CConst s1, CNot (CConst s2, _)) => s1 <> s2
+
+      | _ => false
+
+fun predSimpl (pAll as (p, loc)) =
+    case p of
+       CRoot => pAll
+      | CConst _ => pAll
+      | CPrefix p => (CPrefix (predSimpl p), loc)
+      | CNot p => (CNot (predSimpl p), loc)
+      | CAnd (p1, p2) =>
+       let
+           val p1' = predSimpl p1
+           val p2' = predSimpl p2
+       in
+           case p1' of
+               (CAnd (c1, c2), _) => predSimpl (CAnd (c1, (CAnd (c2, p2'), loc)), loc)
+             | _ => if predImplies (p2', p1') then
+                        p2'
+                    else if predImplies (p1', p2') then
+                        p1'
+                    else
+                        (CAnd (p1', p2'), loc)
+       end
+   
+fun subPred (p1, p2) =
+    if predImplies (p1, p2) then
+       ()
+    else
+       raise (Unify (UnifyPred (p1, p2)))
+
+fun subRecord f (r1, r2) =
+    SM.appi (fn (k, v2) =>
+               case SM.find (r1, k) of
+                   NONE => raise UnequalDomains
+                 | SOME v1 => f (v1, v2)) r2
 
 fun occurs u (t, _) =
     case t of
@@ -186,30 +220,36 @@ fun occurs u (t, _) =
       | TAction (_, d, r) =>
        List.exists (occurs u) (SM.listItems d)
        orelse List.exists (occurs u) (SM.listItems r)
+      | TNested (_, t) => occurs u t
       | TError => false
       | TUnif (_, ref (SOME t)) => occurs u t
       | TUnif (_, u') => u = u'
 
-fun unify (t1All as (t1, _), t2All as (t2, _)) =
+fun subTyp (t1All as (t1, _), t2All as (t2, _)) =
     case (t1, t2) of
        (TBase s1, TBase s2) =>
        if s1 = s2 then
            ()
        else
            raise Unify (UnifyTyp (t1All, t2All))
-      | (TList t1, TList t2) => unify (t1, t2)
+      | (TList t1, TList t2) => subTyp (t1, t2)
       | (TArrow (d1, r1), TArrow (d2, r2)) =>
-       (unify (d1, d2);
-        unify (r1, r2))
+       (subTyp (d2, d1);
+        subTyp (r1, r2))
 
       | (TAction (p1, d1, r1), TAction (p2, d2, r2)) =>
-       ((unifyPred (p1, p2);
-         unifyRecord unify (d1, d2);
-         unifyRecord unify (r1, r2))
+       ((subPred (p2, p1);
+         subRecord subTyp (d2, d1);
+         subRecord subTyp (r1, r2);
+         subRecord subTyp (r2, r1))
         handle UnequalDomains => raise Unify (UnifyTyp (t1All, t2All)))
 
-      | (TUnif (_, ref (SOME t1)), _) => unify (t1, t2All)
-      | (_, TUnif (_, ref (SOME t2))) => unify (t1All, t2)
+      | (TNested (d1, r1), TNested (d2, r2)) =>
+       (subPred (d2, d1);
+        subTyp (r1, r2))
+
+      | (TUnif (_, ref (SOME t1)), _) => subTyp (t1, t2All)
+      | (_, TUnif (_, ref (SOME t2))) => subTyp (t1All, t2)
 
       | (TUnif (_, r1), TUnif (_, r2)) =>
        if r1 = r2 then
@@ -239,6 +279,84 @@ fun isError t =
        (TError, _) => true
       | _ => false
 
+fun whnorm (tAll as (t, loc)) =
+    case t of
+       TUnif (_, ref (SOME tAll)) => whnorm tAll
+      | _ => tAll
+
+fun baseCondition t =
+    case whnorm t of
+       (TBase name, _) => typeRule name
+      | (TList t, _) =>
+       (case baseCondition t of
+            NONE => NONE
+          | SOME f => SOME (fn (EList ls, _) => List.all f ls
+                             | _ => false))
+      | _ => NONE
+
+fun hasTyp (e, t1, t2) =
+    if (case baseCondition t2 of
+           NONE => false
+         | SOME rule => rule e) then
+       ()
+    else
+       subTyp (t1, t2)
+
+fun checkPred G (p, loc) =
+    let
+       val err = ErrorMsg.error (SOME loc)
+    in
+       case p of
+           CRoot => ()
+         | CConst s =>
+           if lookupContext G s then
+               ()
+           else
+               err ("Unbound context " ^ s)
+         | CPrefix p => checkPred G p
+         | CNot p => checkPred G p
+         | CAnd (p1, p2) => (checkPred G p1; checkPred G p2)
+    end
+
+fun checkTyp G (tAll as (t, loc)) =
+    let
+       val err = ErrorMsg.error (SOME loc)
+    in
+       case t of
+           TBase name =>
+           if lookupType G name then
+               tAll
+           else
+               (err ("Unbound type name " ^ name);
+                (TError, loc))
+         | TList t => (TList (checkTyp G t), loc)
+         | TArrow (d, r) => (TArrow (checkTyp G d, checkTyp G r), loc)
+         | TAction (p, d, r) => (checkPred G p;
+                                 (TAction (p, SM.map (checkTyp G) d,
+                                           SM.map (checkTyp G) r), loc))
+         | TNested (p, t) => (checkPred G p;
+                              (TNested (p, checkTyp G t), loc))
+         | TError => raise Fail "TError in parser-generated type"
+         | TUnif _ => raise Fail "TUnif in parser-generated type"
+    end
+
+fun envVarSetFrom v (e, _) =
+    case e of
+       ESet (v', e) =>
+       if v = v' then
+           SOME e
+       else
+           NONE
+      | EGet (_, _, e) => envVarSetFrom v e
+      | ESeq es => foldr (fn (e, found) =>
+                            case found of
+                                SOME _ => found
+                              | NONE => envVarSetFrom v e)
+                        NONE es
+      | ELocal (_, e) => envVarSetFrom v e
+
+      | _ => NONE
+
 fun checkExp G (eAll as (e, loc)) =
     let
        val dte = describe_type_error loc
@@ -254,7 +372,7 @@ fun checkExp G (eAll as (e, loc)) =
                          let
                              val t' = checkExp G e'
                          in
-                             (unify (t', t);
+                             (hasTyp (eAll, t', t);
                               if isError t' then
                                   (TList (TError, loc), loc)
                               else
@@ -274,15 +392,15 @@ fun checkExp G (eAll as (e, loc)) =
                val t =
                    case to of
                        NONE => (newUnif (), loc)
-                     | SOME t => t
+                     | SOME t => checkTyp G t
 
-               val G' = SM.insert (G, x, t)
+               val G' = bindVal G (x, t, NONE)
                val t' = checkExp G' e
            in
                (TArrow (t, t'), loc)
            end
          | EVar x =>
-           (case SM.find (G, x) of
+           (case lookupVal G x of
                 NONE => (dte (UnboundVariable x);
                          (TError, loc))
               | SOME t => t)
@@ -294,8 +412,8 @@ fun checkExp G (eAll as (e, loc)) =
                val tf = checkExp G func
                val ta = checkExp G arg
            in
-               (unify (tf, (TArrow (dom, ran), loc));
-                unify (ta, dom)
+               (hasTyp (func, tf, (TArrow (dom, ran), loc));
+                hasTyp (arg, ta, dom)
                 handle Unify ue =>
                        dte (WrongType ("Function argument",
                                        arg,
@@ -311,8 +429,238 @@ fun checkExp G (eAll as (e, loc)) =
                                        SOME ue));
                        (TError, loc))
            end
-                    
-         | _ => raise Fail "Not ready for that expression yet!"
+
+         | EALam (x, p, e) =>
+           let
+               val p' = checkPred G p
+
+               val G' = bindVal G (x, (TAction (p, SM.empty, SM.empty), loc), NONE)
+               val t' = whnorm (checkExp G' e)
+           in
+               case t' of
+                   (TAction _, _) => (TNested (p, t'), loc)
+                 | _ => (dte (WrongForm ("Body of nested configuration 'fn'",
+                                         "action",
+                                         e,
+                                         t',
+                                         NONE));
+                         (TError, loc))
+           end
+
+         | ESet (evar, e) =>
+           let
+               val t = checkExp G e
+           in
+               (TAction ((CPrefix (CRoot, loc), loc),
+                         SM.empty,
+                         SM.insert (SM.empty, evar, t)),
+                loc)
+           end
+         | EGet (x, evar, rest) =>
+           let
+               val xt = (newUnif (), loc)
+               val G' = bindVal G (x, xt, NONE)
+
+               val rt = whnorm (checkExp G' rest)
+           in
+               case rt of
+                   (TAction (p, d, r), _) =>
+                   (case SM.find (d, evar) of
+                        NONE => (TAction (p, SM.insert (d, evar, xt), r), loc)
+                      | SOME xt' =>
+                        (subTyp (xt', xt)
+                               handle Unify ue =>
+                                      dte (WrongType ("Retrieved environment variable",
+                                                      (EVar x, loc),
+                                                      xt',
+                                                      xt,
+                                                      SOME ue));
+                         rt))
+                 | (TError, _) => rt
+                 | _ => (dte (WrongForm ("Body of environment variable read",
+                                         "action",
+                                         rest,
+                                         rt,
+                                         NONE));
+                         (TError, loc))
+           end
+
+         | ESeq [] => raise Fail "Empty ESeq"
+         | ESeq [e1] => checkExp G e1
+         | ESeq (e1 :: rest) =>
+           let
+               val e2 = (ESeq rest, loc)
+
+               val t1 = whnorm (checkExp G e1)
+               val t2 = whnorm (checkExp G e2)
+           in
+               case t1 of
+                   (TAction (p1, d1, r1), _) =>
+                   (case t2 of
+                        (TAction (p2, d2, r2), _) =>
+                        let
+                            val p' = predSimpl (CAnd (p1, p2), loc)
+
+                            val d' = SM.foldli (fn (name, t, d') =>
+                                                   case SM.find (r1, name) of
+                                                       NONE =>
+                                                       (case SM.find (d', name) of
+                                                            NONE => SM.insert (d', name, t)
+                                                          | SOME t' =>
+                                                            ((case envVarSetFrom name e1 of
+                                                                  NONE => subTyp (t, t')
+                                                                | SOME e => hasTyp (e, t, t'))
+                                                             handle Unify ue =>
+                                                                    dte (WrongType ("Shared environment variable",
+                                                                                    (EVar name, loc),
+                                                                                    t',
+                                                                                    t,
+                                                                                    SOME ue));
+                                                             d'))
+                                                     | SOME t' =>
+                                                       ((case envVarSetFrom name e1 of
+                                                                  NONE => subTyp (t, t')
+                                                                | SOME e => hasTyp (e, t, t'))
+                                                        handle Unify ue =>
+                                                               dte (WrongType ("Shared environment variable",
+                                                                               (EVar name, loc),
+                                                                               t',
+                                                                               t,
+                                                                               SOME ue));
+                                                        d'))
+                                               d1 d2
+
+                            val r' = SM.foldli (fn (name, t, r') => SM.insert (r', name, t))
+                                               r1 r2
+                        in
+                            (TAction (p', d', r'), loc)
+                        end
+                      | (TError, _) => t2
+                      | _ => (dte (WrongForm ("Action to be sequenced",
+                                              "action",
+                                              e2,
+                                              t2,
+                                              NONE));
+                              (TError, loc)))
+                 | (TError, _) => t1
+                 | _ => (dte (WrongForm ("Action to be sequenced",
+                                         "action",
+                                         e1,
+                                         t1,
+                                         NONE));
+                         (TError, loc))
+           end
+
+         | ELocal (e1, e2) =>
+           let
+               val t1 = whnorm (checkExp G e1)
+               val t2 = whnorm (checkExp G e2)
+           in
+               case t1 of
+                   (TAction (p1, d1, r1), _) =>
+                   (case t2 of
+                        (TAction (p2, d2, r2), _) =>
+                        let
+                            val p' = predSimpl (CAnd (p1, p2), loc)
+
+                            val d' = SM.foldli (fn (name, t, d') =>
+                                                   case SM.find (r1, name) of
+                                                       NONE =>
+                                                       (case SM.find (d', name) of
+                                                            NONE => SM.insert (d', name, t)
+                                                          | SOME t' =>
+                                                            ((case envVarSetFrom name e1 of
+                                                                  NONE => subTyp (t', t)
+                                                                | SOME e => hasTyp (e, t', t))
+                                                             handle Unify ue =>
+                                                                    dte (WrongType ("Shared environment variable",
+                                                                                    (EVar name, loc),
+                                                                                    t',
+                                                                                    t,
+                                                                                    SOME ue));
+                                                             d'))
+                                                     | SOME t' =>
+                                                       ((case envVarSetFrom name e1 of
+                                                                  NONE => subTyp (t', t)
+                                                                | SOME e => hasTyp (e, t', t))
+                                                        handle Unify ue =>
+                                                               dte (WrongType ("Shared environment variable",
+                                                                               (EVar name, loc),
+                                                                               t',
+                                                                               t,
+                                                                               SOME ue));
+                                                        d'))
+                                               d1 d2
+                        in
+                            (TAction (p', d', r2), loc)
+                        end
+                      | (TError, _) => t2
+                      | _ => (dte (WrongForm ("Action to be sequenced",
+                                              "action",
+                                              e2,
+                                              t2,
+                                              NONE));
+                              (TError, loc)))
+                 | (TError, _) => t1
+                 | _ => (dte (WrongForm ("Action to be sequenced",
+                                         "action",
+                                         e1,
+                                         t1,
+                                         NONE));
+                         (TError, loc))
+           end
+
+
+         | EWith (e1, e2) =>
+           let
+               val t1 = whnorm (checkExp G e1)
+               val t2 = whnorm (checkExp G e2)
+           in
+               case t1 of
+                   (TNested (pd, (TAction (pr, d1, r1), _)), _) =>
+                   (case t2 of
+                        (TAction (p, d, r), _) =>
+                        if predImplies (pd, p) then
+                            let
+                                val combineRecs =
+                                    SM.unionWithi (fn (name, t1, t2) =>
+                                                      (subTyp (t1, t2)
+                                                       handle Unify ue =>
+                                                              dte (WrongType ("Environment variable",
+                                                                              (EVar name, loc),
+                                                                              t1,
+                                                                              t2,
+                                                                              SOME ue));
+                                                       t2))
+                            in
+                                (TAction (pr, combineRecs (d, d1),
+                                          combineRecs (r, r1)), loc)
+                            end
+                        else
+                            (dte (WrongPred ("nested action",
+                                             pd,
+                                             p));
+                             (TError, loc))
+                      | (TError, _) => t2
+                      | _ =>
+                        (dte (WrongForm ("Body of nested action",
+                                         "action",
+                                         e2,
+                                         t2,
+                                         NONE));
+                         (TError, loc)))
+                 | (TError, _) => t1
+                 | _ =>
+                   (dte (WrongForm ("Container of nested action",
+                                    "action",
+                                    e1,
+                                    t1,
+                                    NONE));
+                    (TError, loc))
+           end
+
+         | ESkip => (TAction ((CPrefix (CRoot, loc), loc),
+                              SM.empty, SM.empty), loc)
     end
 
 exception Ununif
@@ -324,6 +672,7 @@ fun ununif (tAll as (t, loc)) =
       | TArrow (d, r) => (TArrow (ununif d, ununif r), loc)
       | TAction (p, d, r) => (TAction (p, SM.map ununif d, SM.map ununif r), loc)
       | TUnif (_, ref (SOME t)) => ununif t
+      | TNested _ => tAll
       | TError => tAll
 
       | TUnif (_, ref NONE) => raise Ununif
@@ -335,6 +684,7 @@ fun hasError (t, _) =
       | TArrow (d, r) => hasError d orelse hasError r
       | TAction (p, d, r) => List.exists hasError (SM.listItems d)
                             orelse List.exists hasError (SM.listItems r)
+      | TNested _ => false
       | TError => false
       | TUnif (_, ref (SOME t)) => hasError t
       | TUnif (_, ref NONE) => false
@@ -355,4 +705,58 @@ fun checkUnit G (eAll as (_, loc)) =
                    t)
     end
 
+fun checkDecl G (d, _, loc) =
+    case d of
+       DExternType name =>
+       if !externFlag then
+           bindType G name
+       else
+           (ErrorMsg.error (SOME loc) "'extern type' not allowed in untrusted code";
+            G)
+      | DExternVal (name, t) =>
+       if !externFlag then
+           bindVal G (name, checkTyp G t, NONE)
+       else
+           (ErrorMsg.error (SOME loc) "'extern val' not allowed in untrusted code";
+            G)
+      | DVal (name, to, e) =>
+       let
+           val to =
+               case to of
+                   NONE => (newUnif (), loc)
+                 | SOME to => checkTyp G to
+
+           val t = checkExp G e
+       in
+           hasTyp (e, t, to)
+           handle Unify ue =>
+                  describe_type_error loc
+                                      (WrongType ("Bound value",
+                                                  e,
+                                                  t,
+                                                  to,
+                                                  SOME ue));
+           bindVal G (name, to, SOME e)
+       end
+      | DContext name => bindContext G name
+
+fun checkFile G tInit (_, ds, eo) =
+    let
+       val G' = foldl (fn (d, G) => checkDecl G d) G ds
+    in
+       case eo of
+           NONE => ()
+         | SOME (e as (_, loc)) =>
+           let
+               val t = checkExp G' e
+           in
+               hasTyp (e, t, tInit)
+               handle Unify ue =>
+                      (ErrorMsg.error (SOME loc) "Bad type for final expression of source file.";
+                       preface ("Actual:", p_typ t);
+                       preface ("Needed:", p_typ tInit))
+           end;
+       G'
+    end
+
 end