This resolves a compiler ambiguity I hit during development.
In my case, I created an `ArrayHandleDecorator` with one of the arrays being
an `ArrayHandleTransform`. The ambiguity occurs in function
`DecoratorStorageTraits<...>::BuffersToArray`, here an `ArrayHandleTransform`
is constructed using buffers (`std::vector<vtkm::cont::internal::Buffer>`)
This constructor is not defined for `ArrayHandleTransform`, but it's defined for
its superclass (`vtkm::cont::ArrayHandle`). `ArrayHandleTransform` does have a
non-explicit constructor that takes the array to be transformed and the
transform-functor as parameters, where the later has a default value.
This produces the following ambiguous options for the compiler:
1. Create a "to-be-transformed" ArrayHandle instance using the buffers, call
the `ArrayHandleTransform` constructor with this array with the defaulted
functor parameter.
2. Create the superclass instance using the buffer and call the
`ArrayHandleTransform` constructor that takes the superclass.
In this situation, option 2 is the correct choice.
The ambiguity is resolved by marking the constructors that take
buffers as explicit. These constructors are also added for the
derived classess via the `VTK_M_ARRAY_HANDLE_SUBCLASS_IMPL` macro.
fc9077e0c5