Add PromiseStatus enum

minor cleanup

Part of #4604

Author: coke

doc/Type/Promise.rakudoc

@@ -4,7 +4,6 @@
 
 =SUBTITLE Status/result of an asynchronous computation
 
-    my enum PromiseStatus (:Planned(0), :Kept(1), :Broken(2));
     class Promise {}
 
 A C<Promise> is used to handle the result of a computation that might not have
@@ -291,8 +290,9 @@ C<Planned>.
     method status(Promise:D --> PromiseStatus)
 
 Returns the current state of the promise: C<Kept>, C<Broken> or C<Planned>:
+See L<C<PromiseStatus>|/type/PromiseStatus>.
 
-=for code :skip-test<compile time error>
+=for code :preamble<my $promise>
 say "promise got Kept" if $promise.status ~~ Kept;
 
 =head2 method scheduler

doc/Type/PromiseStatus.rakudoc

@@ -0,0 +1,15 @@
+=begin pod :kind("Type") :subkind("enum") :category("basic")
+
+=TITLE enum PromiseStatus
+
+=SUBTITLE Indicate status of a promise
+
+    enum PromiseStatus <Planned Kept Broken>;
+
+X<|Reference,Planned>
+X<|Reference,Kept>
+X<|Reference,Broken>
+An enum for indicating the result of a L<C<Promise>|/type/Promise>.
+Consists of C<Planned>, C<Kept> and C<Broken>.
+
+=end pod