Tune NCVariant.hh fix so it still works with gcc

mctools · May 16, 2024 · 15c2618 · 15c2618
1 parent d1d2963
commit 15c2618
Showing 1 changed file with 4 additions and 3 deletions.
diff --git a/ncrystal_core/include/NCrystal/NCVariant.hh b/ncrystal_core/include/NCrystal/NCVariant.hh
@@ -38,11 +38,12 @@ namespace NCRYSTAL_NAMESPACE {
     //Todo: some of the methods below could be noexcept depending on methods of T1 and T2
   public:
 
-    //conditionally enable default constructor if ALLOW_EMPTY is Yes:
-    template<typename = typename std::enable_if_t<ALLOW_EMPTY==VariantAllowEmpty::Yes>>
+    //Conditionally enable default constructor only if ALLOW_EMPTY is Yes. This
+    //is done using std::enable_if SFINAE magic, which requires a dummy
+    //dependent method template variable U:
+    template<VariantAllowEmpty U = ALLOW_EMPTY, typename = typename std::enable_if<(U==VariantAllowEmpty::Yes)>::type >
     constexpr Variant() noexcept {}
 
-
     //NB: If ALLOW_EMPTY
     Variant( const T1& );
     Variant( T1&& );