From 0f2277e0138f15eaaa646f654523270bf536b4e9 Mon Sep 17 00:00:00 2001
From: "Alejandro R. Mosteo" <amosteo@unizar.es>
Date: Fri, 17 Aug 2018 18:26:11 +0200
Subject: [PATCH] fix iterate on empty tree

---
 src/alire-conditional_trees.adb | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/alire-conditional_trees.adb b/src/alire-conditional_trees.adb
index 0204c52e..ffb43f7e 100644
--- a/src/alire-conditional_trees.adb
+++ b/src/alire-conditional_trees.adb
@@ -417,7 +417,9 @@ package body Alire.Conditional_Trees is
    -----------
 
    overriding function First (Object : Forward_Iterator) return Cursor is
-     (Cursor (Object.Children.First));
+     (if Object.Children.Is_Empty
+      then Cursor (Vectors.No_Element)
+      else Cursor (Object.Children.First));
 
    ----------
    -- Next --
@@ -448,6 +450,10 @@ package body Alire.Conditional_Trees is
    function Iterate (Container : Tree)
                      return Iterators.Forward_Iterator'Class is
    begin
+      if Container.Is_Empty then
+         return Forward_Iterator'(others => <>);
+      end if;
+
       if Container.Kind /= Vector then
          raise Constraint_Error
            with "Cannot iterate over non-vector conditional value";