From fc1e4124a533b7f628dc00d343b9061367634b27 Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Tue, 28 Apr 2015 16:14:30 +0200
Subject: Second iteration over import/export support

---
 build/variable | 10 ++++++++++
 1 file changed, 10 insertions(+)

(limited to 'build/variable')

diff --git a/build/variable b/build/variable
index 59db060..0ccd242 100644
--- a/build/variable
+++ b/build/variable
@@ -67,6 +67,8 @@ namespace build
   struct list_value: value, names
   {
   public:
+    using names::names;
+
     list_value () = default;
     list_value (names d): names (std::move (d)) {}
     list_value (std::string d) {emplace_back (std::move (d));}
@@ -87,6 +89,10 @@ namespace build
   // value_proxy
   //
   // A variable can be undefined, null, or contain some actual value.
+  // Note that once value_proxy is bound to a value, the only way to
+  // rebind it to a different value is by using explicit rebind(). In
+  // particular, assigning one value proxy to another will assing the
+  // values.
   //
   struct variable_map;
 
@@ -148,8 +154,12 @@ namespace build
     //
     const variable_map* map; // Variable map to which this value belongs.
 
+    value_proxy (): map (nullptr), p (nullptr) {}
     value_proxy (value_ptr* p, const variable_map* m): map (m), p (p) {}
 
+    void
+    rebind (const value_proxy& x) {map = x.map; p = x.p;}
+
   private:
     value_ptr* p;
   };
-- 
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