shithub: mc

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Fix recursive types. Again.

	This code does 2 things:
		1) It compares on TID. This shouldn't matter much.
		2) It resolves the type in the substitution map. This
		   prevents us from returning the wrong type.

--- a/parse/infer.c

+++ b/parse/infer.c

@@ -934,7 +934,7 @@

 	/* a ==> b */

 	a = tf(st, u);

 	b = tf(st, v);

-	if (a == b)

+	if (a->tid == b->tid)

 		return a;

 	/* we unify from lower to higher ranked types */

@@ -955,16 +955,8 @@

 	}

 	r = NULL;

-	/*

-	 * unify eagerly here, solving the problem of comparing two specialized types

-	 * that don't have pointer equality.

-	 *

-	 * If the types *actually* conflict, we will error out later in this function,

-	 * and the bogus unification won't matter. If the types *are* the same, though,

-	 * then this short circuits a whole bunch of infinite recursion.

-	 */

-	tytab[a->tid] = b;

 	if (a->type == Tyvar) {

+		tytab[a->tid] = b;

 		ea = basetype(st, a);

 		eb = basetype(st, b);

 		if (ea && eb)

--- a/parse/specialize.c

+++ b/parse/specialize.c

@@ -90,7 +90,7 @@

 	t = tysearch(orig);

 	tmp = substget(tsmap, t);

 	if (tmp)

-		return tmp;

+		return tysearch(tmp);

 	arg = NULL;

 	narg = 0;

 	switch (t->type) {