• Matej Nanut (22/22) Aug 23 2013 Hello!
• Jonathan M Davis (8/36) Aug 23 2013 Because without static it's a member variable, which means that you have...
• Matej Nanut (6/19) Aug 24 2013 But I declared the template static, not the variable.

"Matej Nanut" <matejnanut gmail.com> writes:

Hello!

I've run into this issue that I don't understand, maybe someone 
can enlighten me. :)

This code:
---
struct Thing
{
     int i;
}

void main()
{
     t!(Thing.i)();
}

void t(alias a)()
{
     return;
}
---

fails to compile with: ‘Error: need 'this' for 't' of type 'pure 
nothrow  safe void()'’.

If I declare ‘t’ as static, it works (and does what I want it to 
do).

"Jonathan M Davis" <jmdavisProg gmx.com> writes:

On Friday, August 23, 2013 23:28:46 Matej Nanut wrote:
 Hello!
 
 I've run into this issue that I don't understand, maybe someone
 can enlighten me. :)
 
 This code:
 ---
 struct Thing
 {
 int i;
 }
 
 void main()
 {
 t!(Thing.i)();
 }
 
 void t(alias a)()
 {
 return;
 }
 ---
 
 fails to compile with: ‘Error: need 'this' for 't' of type 'pure
 nothrow  safe void()'’.
 
 If I declare ‘t’ as static, it works (and does what I want it to
 do).

Because without static it's a member variable, which means that you have to 
have a constructed object to access it (since it's part of the object). When 
you declare a variable in a class or struct static, then there's only one for 
the entire class or struct, so it can be accessed without an object. And when 
you do StructName.var or ClassName.var your accessing the variable via the 
struct or class rather than an object, so the variable must be static.

- Jonathan M Davis

"Matej Nanut" <matejnanut gmail.com> writes:

On Friday, 23 August 2013 at 22:54:33 UTC, Jonathan M Davis wrote:
 Because without static it's a member variable, which means that 
 you have to
 have a constructed object to access it (since it's part of the 
 object). When
 you declare a variable in a class or struct static, then 
 there's only one for
 the entire class or struct, so it can be accessed without an 
 object. And when
 you do StructName.var or ClassName.var your accessing the 
 variable via the
 struct or class rather than an object, so the variable must be 
 static.

 - Jonathan M Davis

But I declared the template static, not the variable.

Is there a better way to pass a ‘member get’ expression to a 
template?

I need this for calling ‘.offsetof’ on it, and for checking if 
the member's parent is a certain struct type.