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Generics now bind variables.

    Correctness is not certain.

--- a/parse/gram.y

+++ b/parse/gram.y

@@ -178,6 +178,7 @@

              $$ = $2;}

         | Tgeneric declbody Tendln

             {$2->decl.isconst = 1;

+             $2->decl.isgeneric = 1;

              $$ = $2;}

         | Textern Tvar declbody Tendln

             {$3->decl.isextern = 1;

--- a/parse/htab.c

+++ b/parse/htab.c

@@ -25,6 +25,14 @@

     return ht;

 }

+void htfree(Htab *ht)

+{

+    free(ht->keys);

+    free(ht->vals);

+    free(ht->hashes);

+    free(ht);

+}

+

 static ulong hash(Htab *ht, void *k)

 {

     ulong h;

--- a/parse/infer.c

+++ b/parse/infer.c

@@ -14,6 +14,8 @@

 static Node **postcheck;

 static size_t npostcheck;

+static Htab **tybindings;

+static size_t ntybindings;

 static void infernode(Node *n, Type *ret, int *sawret);

 static void inferexpr(Node *n, Type *ret, int *sawret);

@@ -30,6 +32,19 @@

     st->super = super;

 }

+static int bound(Type *t)

+{

+    ssize_t i;

+    Type *p;

+

+    for (i = ntybindings - 1; i >= 0; i--) {

+        p = htget(tybindings[i], t->pname);

+        if (p == t)

+            return 1;

+    }

+    return 0;

+}

+

 static void tyresolve(Type *t)

 {

     size_t i, nn;

@@ -280,6 +295,13 @@

     *ret = var;

 }

+static Type *freshen(Type *t)

+{

+    if (t->type != Typaram || bound(t))

+        return t;

+    return mktyvar(t->line);

+}

+

 static void inferexpr(Node *n, Type *ret, int *sawret)

 {

     Node **args;

@@ -410,7 +432,7 @@

             if (!s)

                 fatal(n->line, "Undeclared var %s", ctxstr(args[0]));

             else

-                settype(n, s->decl.type);

+                settype(n, freshen(s->decl.type));

             n->expr.did = s->decl.did;

             break;

         case Olit:      /* <lit>:@a::tyclass -> @a */

@@ -475,6 +497,50 @@

     free(k);

 }

+static void tybind(Htab *bt, Type *t)

+{

+    size_t i;

+

+    if (!t)

+        return;

+    if (t->type != Typaram)

+        return;

+

+    if (hthas(bt, t->pname))

+        unify(NULL, htget(bt, t->pname), t);

+    else if (bound(t))

+        return;

+

+    htput(bt, t->pname, t);

+    for (i = 0; i < t->nsub; i++)

+        tybind(bt, t->sub[i]);

+    printf("Bound @%s\n", t->pname);

+}

+

+static void bind(Node *n)

+{

+    Htab *bt;

+

+    if (!n->decl.isgeneric)

+        return;

+    if (!n->decl.init)

+        fatal(n->line, "generic %s has no initializer", n->decl);

+

+    bt = mkht(strhash, streq);

+    lappend(&tybindings, &ntybindings, bt);

+

+    tybind(bt, n->decl.type);

+    tybind(bt, n->decl.init->expr.type);

+}

+

+static void unbind(Node *n)

+{

+    if (!n->decl.isgeneric)

+        return;

+    htfree(tybindings[ntybindings - 1]);

+    lpop(&tybindings, &ntybindings);

+}

+

 static void infernode(Node *n, Type *ret, int *sawret)

 {

     size_t i;

@@ -502,7 +568,9 @@

             popstab();

             break;

         case Ndecl:

+            bind(n);

             inferdecl(n);

+            unbind(n);

             break;

         case Nblock:

             setsuper(n->block.scope, curstab());

@@ -532,6 +600,8 @@

             break;

         case Nfunc:

             setsuper(n->func.scope, curstab());

+            for (i = 0; i < n->func.nargs; i++)

+                tybind(tybindings[ntybindings - 1], n->func.args[i]->decl.type);

             pushstab(n->func.scope);

             inferstab(n->block.scope);

             inferfunc(n);

--- a/parse/parse.h

+++ b/parse/parse.h

@@ -239,6 +239,7 @@

 size_t bscount(Bitset *bs);

 Htab *mkht(ulong (*hash)(void *key), int (*cmp)(void *k1, void *k2));

+void htfree(Htab *ht);

 int htput(Htab *ht, void *k, void *v);

 void *htget(Htab *ht, void *k);

 int hthas(Htab *ht, void *k);