Hello!
This code fails:
-------------------------
void main(){
class A
{ int b; private this(int a){b=a;} }
//{ int b; this(int a){b=a;} }
import std.conv:emplace;
import std.experimental.allocator.mallocator:Mallocator;
import std.experimental.allocator:make;
{
auto ptr = make!A(Mallocator.instance, 42);
assert (ptr.b == 42);
}
}
---------------------------
with error message:
"/usr/include/dmd/phobos/std/conv.d(4115): Error: static assert
"Don't know how to initialize an object of type A with arguments
(int)"
/usr/include/dmd/phobos/std/experimental/allocator/package.d(456):
instantiated from here: emplace!(A, int)
./helloworld.d(25): instantiated from here: make!(A,
shared(Mallocator), int)"
If I make the constructor public, no problem.
It seems that emplace (specialized for classes) doesn't work if
the class has a private constructor.
I added the following snippet to confirm:
----------------------
{
auto ptr =
Mallocator.instance.allocate(__traits(classInstanceSize, A));
auto aPtr = emplace(ptr,34);
assert( aPtr.b == 34 );
}
----------------------
And I get the same error message.
Google gave me:
http://forum.dlang.org/post/kot0t1$uls$1...@digitalmars.com
That guy's ultimate fix was explicitly calling the class's __ctor
method, instead of emplace. The __ctor method is undocumented, as
far as I can tell.
Is there a better solution now? More widespread use of allocators
will likely result in more of this problem.
