VertexBuffer x;

  Error: struct VertexBuffer(VertexDataType = void) is used as a type

auto y = VertexBuffer();

  Error: struct VertexBuffer(VertexDataType = void) cannot deduce template function from argument types !()()

But this works:

VertexBuffer!() z;

Why should I need to supply an empty argument list? This defeats the purpose of the default arg, and obscures my code in the common case.

Untyped vertex buffers are the default, and it would be nice to be able to declare them trivially.

Also, those error messages are quite unhelpful.