shithub: mc

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Fix unification of sequence types.

    We shoudl be unifying them with an index hack, which is the only
    way to guarantee that t->sub[0] will be present.

--- a/parse/infer.c

+++ b/parse/infer.c

@@ -1264,6 +1264,7 @@

     Node *s;

     size_t nbound;

     Node **bound;

+    Type *t;

     if (!n)

         return;

@@ -1328,8 +1329,10 @@

             infernode(st, n->iterstmt.seq, NULL, sawret);

             infernode(st, n->iterstmt.body, ret, sawret);

+            t = mktyidxhack(n->line, mktyvar(n->line));

             constrain(st, n, type(st, n->iterstmt.seq), cstrtab[Tcidx]);

-            unify(st, n, type(st, n->iterstmt.elt), type(st, n->iterstmt.seq)->sub[0]);

+            unify(st, n, type(st, n->iterstmt.seq), t);

+            unify(st, n, type(st, n->iterstmt.elt), t->sub[0]);

             break;

         case Nmatchstmt:

             infernode(st, n->matchstmt.val, NULL, sawret);