From 5c369faa461ec4416d2d4b231a5b36963a7315ce Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Mon, 4 Apr 2016 13:06:50 +0200
Subject: Implement value typing, null support via value attributes

For example:

v = [null]
v = [string] abc
v += ABC # abcABC
---
 build2/variable | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

(limited to 'build2/variable')

diff --git a/build2/variable b/build2/variable
index 48acfea..10a0f59 100644
--- a/build2/variable
+++ b/build2/variable
@@ -120,14 +120,16 @@ namespace build2
     //
     //
   public:
-    ~value () {if (!null ()) *this = nullptr;}
+    ~value () {*this = nullptr;}
 
     explicit
     value (const value_type* t = nullptr)
         : type (t), state (value_state::null) {}
 
+    // Note: preserves type.
+    //
     value&
-    operator= (nullptr_t);
+    operator= (nullptr_t) {if (!null ()) reset (); return *this;}
 
     value (value&&);
     explicit value (const value&);
@@ -185,6 +187,10 @@ namespace build2
     // Make sure we have sufficient storage for untyped values.
     //
     static_assert (sizeof (names) <= size_, "insufficient space");
+
+  private:
+    void
+    reset ();
   };
 
   // The values should be of the same type (or both be untyped). NULL values
-- 
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