shithub: mc

Info  •  Files  •  Log  •  Branches

Give better errors on infinite types.

	We used to miss some of them, and we used to givea
	a confusing error about incompatibility.

--- a/parse/infer.c

+++ b/parse/infer.c

@@ -262,7 +262,7 @@

  * Recursive types that contain themselves through

  * pointers or slices are fine, but any other self-inclusion

  * would lead to a value of infinite size */

-static int tyinfinite(Inferstate *st, Type *t, Type *sub)

+static int occurs(Inferstate *st, Type *t, Type *sub)

 {

 	size_t i;

@@ -278,20 +278,21 @@

 	switch (sub->type) {

 	case Tystruct:

 		for (i = 0; i < sub->nmemb; i++)

-			if (tyinfinite(st, t, decltype(sub->sdecls[i])))

+			if (occurs(st, t, decltype(sub->sdecls[i])))

 				return 1;

 		break;

 	case Tyunion:

 		for (i = 0; i < sub->nmemb; i++) {

-			if (sub->udecls[i]->etype && tyinfinite(st, t, sub->udecls[i]->etype))

+			if (sub->udecls[i]->etype && occurs(st, t, sub->udecls[i]->etype))

 				return 1;

 		}

 		break;

 	case Typtr:

-	case Tyslice: return 0;

+	case Tyslice: 

+		return 0;

 	default:

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

-			if (tyinfinite(st, t, sub->sub[i]))

+			if (occurs(st, t, sub->sub[i]))

 				return 1;

 		break;

 	}

@@ -426,7 +427,7 @@

 		bsunion(t->traits, base->traits);

 	else if (base->traits)

 		t->traits = bsdup(base->traits);

-	if (tyinfinite(st, t, NULL))

+	if (occurs(st, t, NULL))

 		lfatal(t->loc, "type %s includes itself", tystr(t));

 	st->ingeneric--;

 	if (t->type == Tyname || t->type == Tygeneric) {

@@ -784,21 +785,6 @@

 	}

 }

-/* Tells us if we have an index hack on the type */

-/* prevents types that contain themselves in the unification;

- * eg @a U (@a -> foo) */

-static int occurs(Type *a, Type *b)

-{

-	size_t i;

-

-	if (a == b)

-		return 1;

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

-		if (occurs(a, b->sub[i]))

-			return 1;

-	return 0;

-}

-

 /* Computes the 'rank' of the type; ie, in which

  * direction should we unify. A lower ranked type

  * should be mapped to the higher ranked (ie, more

@@ -954,6 +940,13 @@

 		free(to);

 	}

+	/* Disallow recursive types */

+	if (a->type == Tyvar && b->type != Tyvar) {

+		if (occurs(st, a, b))

+			fatal(ctx, "%s occurs within %s, leading to infinite type near %s\n",

+				tystr(a), tystr(b), ctxstr(st, ctx));

+	}

+

 	r = NULL;

 	if (a->type == Tyvar) {

 		tytab[a->tid] = b;

@@ -962,12 +955,6 @@

 		if (ea && eb)

 			unify(st, ctx, ea, eb);

 		r = b;

-	}

-

-	/* Disallow recursive types */

-	if (a->type == Tyvar && b->type != Tyvar) {

-		if (occurs(a, b))

-			typeerror(st, a, b, ctx, "Infinite type\n");

 	}

 	if (a->type == Tyarray && b->type == Tyarray) {

--- a/parse/type.c

+++ b/parse/type.c

@@ -515,7 +515,8 @@

 	char *end;

 	char *sep;

-	t = tysearch(t);

+	if (t)

+		t = tysearch(t);

 	sep = "";

 	p = buf;

 	end = p + len;