From 0430f3e693ae5ea84c54fb30ef19ce0c8ff77bfc Mon Sep 17 00:00:00 2001
From: Dan Kortschak <dan@kortschak.io>
Date: Wed, 25 Nov 2020 13:47:53 +1030
Subject: [PATCH] graph: make state of empty less contradictory and provide
 debugging strings

---
 graph/nodes_edges.go | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/graph/nodes_edges.go b/graph/nodes_edges.go
index 35b420b2..57551d7b 100644
--- a/graph/nodes_edges.go
+++ b/graph/nodes_edges.go
@@ -286,9 +286,9 @@ var (
 	_ WeightedLineSlicer = Empty
 )
 
-const nothing = empty(true)
+const nothing = empty(0)
 
-type empty bool
+type empty int
 
 func (empty) Next() bool                        { return false }
 func (empty) Len() int                          { return 0 }
@@ -303,3 +303,6 @@ func (empty) Line() Line                        { return nil }
 func (empty) LineSlice() []Line                 { return nil }
 func (empty) WeightedLine() WeightedLine        { return nil }
 func (empty) WeightedLineSlice() []WeightedLine { return nil }
+
+func (empty) String() string   { return "<empty>" }
+func (empty) GoString() string { return "graph.Empty" }