On Tuesday, 15 May 2018 at 15:02:36 UTC, jmh530 wrote:
On Tuesday, 15 May 2018 at 14:52:46 UTC, Steven Schveighoffer
wrote:
[snip]
It seems opDispatch isn't being used in the with statement.
That seems like a bug, or maybe a limitation. I'm not sure how
"with" works, but I assumed it would try calling as a member,
and then if it doesn't work, try the call normally. Probably
it's checking to see if it has that member first.
Annoying...
-Steve
Looks like with statements ignore opDispatch.
struct Foo(int x)
{
auto opDispatch(string s)()
if (s == "bar")
{
return x++;
}
}
void main()
{
int y = 0;
with(Foo!1)
{
y = bar; //error: undefined identifier bar
}
assert(y == 2);
}
You've got bugs in your code: ++x has to fail for the template
case, since you're trying to increment a compile-time value. This
is what the call to bar is lowered to:
Foo!1.opDispatch!"bar"()
When you try and compile that, you get these error messages:
Error: cannot modify constant 1
Error: template instance `foo.Foo!1.Foo.opDispatch!"bar"` error
instantiating
In addition, the with-statement in your code refers to the type
Foo!1, not an instance of it. Fixed code:
struct Foo(int x)
{
int n = x;
auto opDispatch(string s)()
if (s == "bar")
{
n++;
return n;
}
}
unittest
{
int y = 0;
with(Foo!1())
{
y = bar; // Works!
}
assert(y == 2);
}
--
Simen
