Christopher Wright wrote:
Andrei Alexandrescu wrote:
Christopher Wright wrote:
What information did you find that you needed but is not available in
TypeInfo?
To have constant-type dispatching without limitations you need the
static type information.
What do you mean by this? At first I thought you meant that TypeInfo
does not contain sufficient information to determine whether something
is const or immutable, but that is not the case. If you wish to convert
a Variant of a mutable thing to a const version of it, then you can
check whether the type you get is convertible, and without any trouble
-- the template instantiation to get the appropriate type will provide
the TypeInfo you need.
So what's the issue?
You may want to peruse the std.variant implementation. Variant is a
struct containing a buffer for the data and a pointer to function. The
function is a dispatcher for a handful of primitive operations.
The pointer to function is assigned from the address of a function
template. To get that address, you need the static type. That's the
necessity.
It's a very fast and very flexible design, but it does need the static
type during initialization.
Andrei
