On Sunday, 7 April 2019 at 05:24:38 UTC, Alex wrote:
Error: template instance `Reflect!(type)` cannot use local
`type` as parameter to non-global template `Reflect(Ts...)()`
mixin(`import `~moduleName!(T)~`;`);
mixin(`alias X = T.`~name~`;`);
super.Reflect!(X);
I realize X is local but I'm trying to figure out why it can't
be passed to a "non-global" template.
- In DMD, objects may have at most one scope (which can be a
class, struct, or stack frame).
- Instantiating a template with a scoped object makes the
template have the same scope as the object.
- If a template is already scoped (non-global), then it thus
cannot have a second scope. Hence the error.
IIRC there is an experimental pull request which removes this
limitation.
Workarounds:
- Make either the template or the argument global (non-scoped)
- Instead of passing the object as a template parameter, pass it
as a runtime parameter with a type encapsulating the object. Each
runtime parameter may be scoped, thus bypassing the limitation.
I'm not sure this applies to your use case, if the Reflect
template needs to perform compile-time introspection on the
parameter.
- If you just need to pass the type, typeof(X) should work of
course.
