From 67b36b32e19e17db9b1e5c72deb8db7202a0f41b Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Thu, 9 Aug 2018 09:36:23 +0200
Subject: Add support for returning optional<T> from (buildfile) function
 implementations

---
 build2/variable.ixx | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

(limited to 'build2/variable.ixx')

diff --git a/build2/variable.ixx b/build2/variable.ixx
index 8c16559..bf5fb92 100644
--- a/build2/variable.ixx
+++ b/build2/variable.ixx
@@ -24,6 +24,14 @@ namespace build2
     new (&data_) names (move (ns));
   }
 
+  inline value::
+  value (optional<names> ns)
+      : type (nullptr), null (!ns), extra (0)
+  {
+    if (!null)
+      new (&data_) names (move (*ns));
+  }
+
   template <typename T>
   inline value::
   value (T v)
@@ -33,6 +41,18 @@ namespace build2
     null = false;
   }
 
+  template <typename T>
+  inline value::
+  value (optional<T> v)
+      : type (&value_traits<T>::value_type), null (true), extra (0)
+  {
+    if (v)
+    {
+      value_traits<T>::assign (*this, move (*v));
+      null = false;
+    }
+  }
+
   inline value& value::
   operator= (reference_wrapper<value> v)
   {
-- 
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