shithub: mc

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Be better about unifying instead of just overwriting.

	In rare conditions we were clobbering the shifting up of
	the delayed type, which would lead to a spurious type error.

--- a/parse/infer.c

+++ b/parse/infer.c

@@ -1391,9 +1391,7 @@

 			isconst = isconst && args[i]->expr.isconst;

 		}

 	}

-	if (exprop(n) == Ovar)

-		n->expr.isconst = decls[n->expr.did]->decl.isconst;

-	else if (opispure[exprop(n)])

+	if (opispure[exprop(n)])

 		n->expr.isconst = isconst;

 	*exprconst = n->expr.isconst;

 }

@@ -1930,11 +1928,14 @@

 	base = htget(st->seqbase, orig);

 	if (orig->type == Tyvar && hthas(st->delayed, orig)) {

 		delayed = htget(st->delayed, orig);

-		if (t->type == Tyvar)

-			t = delayed;

-		else if (tybase(t)->type != delayed->type && !noerr)

+		if (t->type == Tyvar) {

+			/* tyvar is guaranteed to unify error-free */

+			unify(st, ctx, t, delayed);

+			t = tf(st, t);

+		} else if (tybase(t)->type != delayed->type && !noerr) {

 			fatal(ctx, "type %s not compatible with %s near %s\n", tystr(t),

 					tystr(delayed), ctxstr(st, ctx));

+		}

 	}

 	if (t->type == Tyvar) {

 		if (hastrait(t, traittab[Tcint]) && checktraits(t, tyint))