On Saturday, 16 May 2015 at 02:08:09 UTC, weaselcat wrote:
On Saturday, 16 May 2015 at 02:06:45 UTC, weaselcat wrote:
very long standing compiler bug
https://issues.dlang.org/show_bug.cgi?id=3051
see also
https://issues.dlang.org/show_bug.cgi?id=5710
unsure if they're duplicate bugs, never really looked into it.
Yeah it looks like the bugs come from the same root cause.
http://wiki.dlang.org/DIP30
Also, this came up during the discussion of the latter bug. Its
still in "Draft" status. Haven't read it carefully enough yet to
tell whether or not it would be helpful.
GDC rejects this code as well. I dunno about LDC.
BUT!! I found a way to make this pattern, at least, work as
intended. I expected a symbol resolution error from the following
code but was very pleased to find that it compiles:
module ffunc;
struct F (T)
{
T a;
}
auto ref fmap (alias f, T)(auto ref F!T x)
{
return F!T (f(x.a));
}
---
module gfunc;
struct G (T)
{
T a;
}
auto ref fmap (alias f, T)(auto ref G!T x)
{
return G!T (f(x.a));
}
---
import ffunc;
import gfunc;
auto ref identity (T)(auto ref T a)
{
return a;
}
void main ()
{
F!int a;
G!int b;
a.fmap!identity;
b.fmap!identity;
static auto id (T)(T x)
{return x;}
a.fmap!id;
b.fmap!id;
a.fmap!((int x) => x);
b.fmap!((int x) => x);
a.fmap!(x => x);
b.fmap!(x => x);
}
Frankly this is even better than the original code, because now
fmap can be defined after the functor, as a UFCS extension.
Awesome!!
