On 2/21/20 5:15 AM, drug wrote:
Currently this code does not compiles:
```
unittest
{
class MyClass
{
T opCall(T)(T p)
{
return p;
}
}
import std.container.array : Array;
Array!MyClass arr;
}
```
but if you comment out `opCall` in MyClass this code compiles. This is
caused by this in std.conv(4434):
```
static if (is(typeof(chunk = T(args))))
chunk = T(args);
```
The reason is that `is(typeof(chunk = T(args)))` returns true but does
not compiles becase MyClass has `opCall`, compiler calls `opCall` but it
needs `this` pointer that is unavailable. I replaced it by
```
static if (__traits(compiles, chunk = T(args)))
chunk = T(args);
```
it works but I'm not sure this good solution. The question is -
shouldn't `typeof` return false in this case? if so then the right fix
would be fix typeof.
This is a bug for is(typeof). It should indeed reject that call.
My understanding about __traits(compiles) is that it does some funky
things in terms of allowing compilation that isn't normally allowed,
which is a reason to prefer is(typeof). There are probably bugzilla
issues on this. I remember compiler gurus (maybe Timon?) talking about
this at one point.
I would say file an issue with a minimal test case. Any time you have:
static if(is(typeof(expr))) expr;
It should not error (excepting that there are some cases, such as
expressions which can't technically be statements).
-Steve
