On 11/13/16 11:29 AM, Jonathan Marler wrote:
It looks like an Appender field of a struct doesn't work when its
element type is the containing struct, i.e.
struct Foo
{
Appender!(Foo[]) fooAppender;
}
My guess is the problem is that the Appender needs to know how big "Foo"
is since it would be storing each element by value, but since Foo's size
depends on the size of the appender, we have a circular dependency on
knowing the storage size.
This theory is reinforced because modifying the element type of
fooAppender to "Foo*" fixes the problem.
struct Foo
{
Appender!(Foo*[]) fooAppender; // Works fine
}
One odd thing is that this error doesn't manifest until the appender is
used. It compiles just fine so long as you don't actually use the
appender, but once you put something in it or access the data, you will
get a compiler error at the location where it was used, and not at the
place where the appender was defined. I'm not sure how it does this,
but from the error messages I've seen, it looks like the appender may be
setting the element type to "void" and silently continuing on as if this
isn't a problem.
This is probably because Appender's functions are all templates.
A Foo[] can be stored in a Foo, because it doesn't need the size. But
yes, as soon as you start needing Appender functions, then the compiler
chokes.
It is a forward reference bug, but still a bug IMO. If you can store the
appender, then the compiler knows how big it has to be. So it should be
fine at that point.
Paging Timon, I'm betting your front end handles this just fine ;)
-Steve
