From cc3ed94bd6dd5407f27c39502838df1558bdb583 Mon Sep 17 00:00:00 2001
From: Vadim Belman <vrurg@lflat.org>
Date: Tue, 8 Feb 2022 20:31:22 -0500
Subject: [PATCH] Turn junctions into value objects

This may serve many purposes like classification/categorization over
junctions; or ensuring a junction we have is the one we expect.
---
 src/Perl6/bootstrap.c/BOOTSTRAP.nqp |  1 +
 src/core.c/Junction.pm6             | 16 ++++++++++++++++
 2 files changed, 17 insertions(+)

diff --git a/src/Perl6/bootstrap.c/BOOTSTRAP.nqp b/src/Perl6/bootstrap.c/BOOTSTRAP.nqp
index 7f6ca85dcfe..02a86055e18 100644
--- a/src/Perl6/bootstrap.c/BOOTSTRAP.nqp
+++ b/src/Perl6/bootstrap.c/BOOTSTRAP.nqp
@@ -3780,6 +3780,7 @@ BEGIN {
     Junction.HOW.add_parent(Junction, Mu);
     Junction.HOW.add_attribute(Junction, scalar_attr('$!eigenstates', Mu, Junction));
     Junction.HOW.add_attribute(Junction, scalar_attr('$!type', str, Junction));
+    Junction.HOW.add_attribute(Junction, Attribute.new(:name<$!WHICH>, :type(ValueObjAt), :package(Junction)));
     Junction.HOW.compose_repr(Junction);
 
     # class Bool is Int {
diff --git a/src/core.c/Junction.pm6 b/src/core.c/Junction.pm6
index 6243a8a1f78..c0ed7e5b57e 100644
--- a/src/core.c/Junction.pm6
+++ b/src/core.c/Junction.pm6
@@ -176,6 +176,22 @@ my class Junction { # declared in BOOTSTRAP
         )
     }
 
+    multi method WHICH(Junction:D: --> ValueObjAt:D) {
+        nqp::if(
+            nqp::defined($!WHICH),
+            $!WHICH,
+            ($!WHICH := nqp::box_s(
+                nqp::concat(
+                    nqp::if(
+                        nqp::eqaddr(self.WHAT, Junction),
+                        'Junction|',
+                        nqp::concat(nqp::unbox_s(self.^name), '|')
+                    ),
+                    nqp::sha1(self.gist)
+                ),
+                ValueObjAt )));
+    }
+
     multi method ACCEPTS(Junction:U: Junction:D --> True) { }
     multi method ACCEPTS(Junction:D \SELF: Junction:D \topic) {
         topic.BOOLIFY-ACCEPTS(self)