classes.maybe: Change the type of maybe's class slot. As a result, maybe: maybe: integer is valid now, so fix the unit tests and its prettyprinting.

basis/prettyprint/prettyprint-tests.factor

@@ -449,3 +449,9 @@ TUPLE: fo { a intersection{ fixnum integer } initial: 0 } ;
 ] [
     [ maybe: union{ float integer } . ] with-string-writer
 ] unit-test
+
+[
+"""maybe: maybe: integer\n"""
+] [
+    [ maybe: maybe: integer . ] with-string-writer
+] unit-test

core/classes/maybe/maybe-tests.factor

@@ -28,7 +28,9 @@ PREDICATE: natural < maybe: integer
 [ f ] [ 0 natural? ] unit-test
 [ t ] [ 1 natural? ] unit-test
 
-[ "USE: math maybe: maybe: integer" eval( -- obj ) ] [ error>> bad-slot-value? ] must-fail-with
+[ t ] [ f maybe: maybe: integer instance? ] unit-test
+[ t ] [ 3 maybe: maybe: integer instance? ] unit-test
+[ f ] [ 3.03 maybe: maybe: integer instance? ] unit-test
 
 INTERSECTION: only-f maybe: integer POSTPONE: f ;
 

core/classes/maybe/maybe.factor

@@ -5,7 +5,12 @@ classes.algebra.private classes.private classes.union.private
 effects kernel words ;
 IN: classes.maybe
 
-TUPLE: maybe { class classoid initial: object read-only } ;
+! The class slot has to be a union of a word and a classoid
+! for TUPLE: foo { a maybe: foo } ; and maybe: union{ integer float } to work.
+! In the first case, foo is not yet a tuple-class when maybe: is reached,
+! thus it's not a classoid yet. union{ is a classoid, so the second case works.
+! words are not generally classoids, so classoid alone is insufficient.
+TUPLE: maybe { class union{ word classoid } initial: object read-only } ;
 
 C: <maybe> maybe