Merge topic 'missing-template-arg-list' into release-2.0

8bd6ebac Fix clang compile issue with a missing tempolate arg list

Acked-by: Kitware Robot <kwrobot@kitware.com>
Acked-by: Vicente Bolea <vicente.bolea@kitware.com>
Merge-request: !3275

docs/changelog/missing-template-arg-list.md

+## Fix clang compile issue with a missing tempolate arg list
+
+Apparently, starting with LLVM clang version 20, if you use the `template`
+keyword to highlight a sub-element, you have to provide a template argument
+list. This is true even for a method where the template arguments can be
+completely determined by the types of the arguments. Fix this problem by
+providing an empty template arg list (so the compiler knows what is
+templated but still figures out its own types).
+
+Fixes #830

vtkm/internal/VariantImplDetail.h

@@ -548,7 +548,7 @@ struct VariantCases
         // just the one that it currently holds.
         return f(storage.V7, std::forward<Args>(args)...);
       default:
-        return VariantCases<NumCases - 8>::template CastAndCall(
+        return VariantCases<NumCases - 8>::template CastAndCall<>(
           index - 8, std::forward<Functor>(f), storage.Remaining, std::forward<Args>(args)...);
     }
   }

vtkm/internal/VariantImplDetail.h.in

@@ -273,7 +273,7 @@ $for(param_index in range(max_expanded))\
         return f(storage.V$(param_index), std::forward<Args>(args)...);
 $endfor\
       default:
-        return VariantCases<NumCases - $(max_expanded)>::template CastAndCall(
+        return VariantCases<NumCases - $(max_expanded)>::template CastAndCall<>(
           index - $(max_expanded), std::forward<Functor>(f), storage.Remaining, std::forward<Args>(args)...);
     }
   }