[PATCH 2/3] variants: minor improvements

[Theophile Ranquet]

* data/variant.hh (swap): More asserts can't hurt.
(variant): Prohibit copy construction.

diff --git a/data/variant.hh b/data/variant.hh
index 1ebcfe8..afa825e 100644
--- a/data/variant.hh
+++ b/data/variant.hh
@@ -165,6 +165,8 @@ m4_define([b4_variant_define],
     inline void
     swap (variant<S>& other)
     {]b4_parse_assert_if([
+      YYASSERT (built);
+      YYASSERT (other.built);
       YYASSERT (tname == other.tname);])[
       std::swap (as<T>(), other.as<T>());]b4_parse_assert_if([
       std::swap (built, other.built);
@@ -208,6 +210,11 @@ m4_define([b4_variant_define],
       abort ();
     }
 
+    variant (const self_type&)
+    {
+      abort ();
+    }
+
   private:
     /// A buffer large enough to store any of the semantic values.
     /// Long double is chosen as it has the strongest alignment
-- 
1.8.1