shithub: mc

Info  •  Files  •  Log  •  Branches

Push down named unions types into union tags

	Currently, union tags are given the type of their
	enclosing union, by default:

		type u = union
			`Foo
		;;

		var x = `Foo

	will currently infer the variable 'x' as having type
	'union `Foo ;;'. To make the type of 'x' infer as 'foo',
	the code needs to force 'x' to unify with something that is
	explicitly declared as a 'u'.

	This change makes it so that union tags declared in the manner
	above will default to type 'u', instead. This is a special case,
	but it makes the behavior less surprising.

--- a/doc/lang.txt

+++ b/doc/lang.txt

@@ -1,6 +1,6 @@

                     The Myrddin Programming Language

                               Jul 2012

-                          Updated Feb 2017

+                          Updated Jul 2018

                             Ori Bernstein

 TABLE OF CONTENTS:

@@ -784,6 +784,16 @@

             with type $t :: numeric $t, integral $t is replaced with int. An

             unconstrained type with $t :: numeric $t, floating $t is replaced with

             flt64.

+

+	    As a special case, a union type declared with the form

+

+	        type u = union

+                    `Foo

+		;;

+

+            will have the default type set to the named type, and not the

+            union itself. This is slightly inconsistent, but it makes the

+            behavior less surprising.

     4.6. Built In Traits:

--- a/parse/gram.y

+++ b/parse/gram.y

@@ -36,6 +36,7 @@

 static void setwith(Type *ty, Traitspec **spec, size_t nspec);

 static void setupinit(Node *n);

 static void addinit(Node *blk, Node *dcl);

+static void setuname(Type *ty);

 %}

@@ -528,6 +529,7 @@

 			$$.type = mktyname($2.loc, mkname($2.loc, $2.name), $5);

 		else

 			$$.type = mktygeneric($2.loc, mkname($2.loc, $2.name), $2.params, $2.nparams, $5);

+		setuname($$.type);

 		setwith($$.type, $3.spec, $3.nspec);

 	}

 	;

@@ -1147,6 +1149,17 @@

 	n->decl.name->name.name = strdup(s);

 }

+static void

+setuname(Type *ty)

+{

+	size_t i;

+

+	if (ty->sub[0]->type != Tyunion)

+		return;

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

+		ty->sub[0]->udecls[i]->utype = ty;

+}

+

 static Node *

 mkpseudodecl(Srcloc l, Type *t)

 {

@@ -1231,7 +1244,8 @@

 		break;

 	case Tyunion:

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

-			b->udecls[i]->utype = b;

+			if (!b->udecls[i]->utype)

+				b->udecls[i]->utype = b;

 			b->udecls[i]->id = i;

 			putucon(st, b->udecls[i]);

 		}

--- a/parse/infer.c

+++ b/parse/infer.c

@@ -514,7 +514,7 @@

 	case Tyunion:

 		inaggr++;

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

-			t->udecls[i]->utype = t;

+			assert(t->udecls[i]->utype);

 			t->udecls[i]->utype = tf(t->udecls[i]->utype);

 			if (t->udecls[i]->etype) {

 				tyresolve(t->udecls[i]->etype);

@@ -1498,7 +1498,11 @@

 	 *

 	 * To make it compile, for now, we just bind the types in here.

 	 */

-	t = tysubst(tf(uc->utype), uc->utype);

+	t = uc->utype;

+	if (t->type != Tyunion)

+		t = t->sub[0];

+	assert(t->type == Tyunion);

+	t = tysubst(tf(t), t);

 	uc = tybase(t)->udecls[uc->id];

 	if (uc->etype) {

 		inferexpr(&n->expr.args[1], NULL, NULL);