shithub: mc

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Fix up type index hacks a bit.

    We rank and order types by their unifiability.

--- a/parse/infer.c

+++ b/parse/infer.c

@@ -335,18 +335,8 @@

     }

 }

-static int idxhacked(Type **pa, Type **pb)

+static int idxhacked(Type *a, Type *b)

 {

-    Type *a, *b;

-

-    a = *pa;

-    b = *pb;

-    /* we want to unify Tyidxhack => concrete indexable. Flip 

-     * to make this happen, if needed */

-    if (b->type == Tyvar && b->nsub > 0) {

-        *pb = a;

-        *pa = b;

-    }

     return (a->type == Tyvar && a->nsub > 0) || a->type == Tyarray || a->type == Tyslice;

 }

@@ -364,6 +354,16 @@

     return 0;

 }

+static int tyrank(Type *t)

+{

+    if (t->type == Tyvar && t->nsub == 0)

+        return 0;

+    if (t->type == Tyvar && t->nsub > 0)

+        return 1;

+    else

+        return 2;

+}

+

 static Type *unify(Inferstate *st, Node *ctx, Type *a, Type *b)

 {

     Type *t;

@@ -375,7 +375,7 @@

     b = tf(st, b);

     if (a == b)

         return a;

-    if (b->type == Tyvar) {

+    if (tyrank(b) < tyrank(a)) {

         t = a;

         a = b;

         b = t;

@@ -391,7 +391,7 @@

         if (occurs(a, b))

             fatal(ctx->line, "Infinite type %s in %s near %s", tystr(a), tystr(b), ctxstr(st, ctx));

-    if (a->type == b->type || idxhacked(&a, &b)) {

+    if ((a->type == b->type || idxhacked(a, b)) && tyrank(a) != 0) {

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

             /* types must have same arity */

             if (i >= a->nsub)

--- a/parse/type.c

+++ b/parse/type.c

@@ -403,7 +403,7 @@

             p += snprintf(p, end - p, "@$%d", t->tid);

             if (t->nsub) {

                 p += snprintf(p, end - p, "(");

-                for (i = 1; i < t->nsub; i++) {

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

                     p += snprintf(p, end - p, "%s", sep);

                     p += tybfmt(p, end - p, t->sub[i]);

                     sep = ", ";

-- 

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