• Andre Pany (12/12) Jan 31 2019 Hi,
• Steven Schveighoffer (3/18) Jan 31 2019 Most likely it's a direct translation from a C preprocessor macro.
• Seb (5/17) Jan 31 2019 Have you tried changing it to alias and check whether the
• Adam D. Ruppe (15/18) Jan 31 2019 If my memory is correct, it is actually for old D compatibility.
• Kagamin (14/14) Jan 31 2019 It's a strong typed handle, in C it's declared as
• Andre Pany (8/22) Feb 01 2019 Thanks for all answers.
• Andre Pany (3/26) Feb 26 2019 Issue created

Andre Pany <andre s-e-a-p.de> writes:

Hi,

I noticed in druntime this template is used often:

package template DECLARE_HANDLE(string name, base = HANDLE) {
     mixin ("alias " ~ base.stringof ~ " " ~ name ~ ";");

The disadvantage is, IDEs like IntelliJ are not able to find the 
symbols using this template e.g.
mixin DECLARE_HANDLE!("SC_HANDLE");

What is the benefit of this template?
Why can't we just use
alias HANDLE SC_HANDLE;

Kind regards
Andre

Steven Schveighoffer <schveiguy gmail.com> writes:

On 1/31/19 3:51 PM, Andre Pany wrote:
 Hi,
 
 I noticed in druntime this template is used often:
 
 package template DECLARE_HANDLE(string name, base = HANDLE) {
      mixin ("alias " ~ base.stringof ~ " " ~ name ~ ";");
 
 The disadvantage is, IDEs like IntelliJ are not able to find the symbols 
 using this template e.g.
 mixin DECLARE_HANDLE!("SC_HANDLE");
 
 What is the benefit of this template?
 Why can't we just use
 alias HANDLE SC_HANDLE;
 

Most likely it's a direct translation from a C preprocessor macro.

-Steve

Seb <seb wilzba.ch> writes:

On Thursday, 31 January 2019 at 20:51:37 UTC, Andre Pany wrote:
 Hi,

 I noticed in druntime this template is used often:

 package template DECLARE_HANDLE(string name, base = HANDLE) {
     mixin ("alias " ~ base.stringof ~ " " ~ name ~ ";");

 The disadvantage is, IDEs like IntelliJ are not able to find 
 the symbols using this template e.g.
 mixin DECLARE_HANDLE!("SC_HANDLE");

 What is the benefit of this template?
 Why can't we just use
 alias HANDLE SC_HANDLE;

 Kind regards
 Andre

Have you tried changing it to alias and check whether the 
testsuite still passes?
Druntime is a bit old, so I wouldn't be too surprised if this is 
an old relict.

Adam D. Ruppe <destructionator gmail.com> writes:

On Thursday, 31 January 2019 at 20:51:37 UTC, Andre Pany wrote:
 I noticed in druntime this template is used often:

 package template DECLARE_HANDLE(string name, base = HANDLE) {
     mixin ("alias " ~ base.stringof ~ " " ~ name ~ ";");

If my memory is correct, it is actually for old D compatibility. 
It used to do `version(D1) typedef, else alias`.

You can see in the code right above it that there is a commented 
struct and a usage of library Typedef too. A little bit further 
up is a comment about Typedef being because of new versions of D 
deprecating the keyword.

Old typedef fit the bill quite nicely, but it got deprecated and 
removed from the language. These headers used to be usable for 
various versions of D, and the mixin string lets you use keywords 
that no longer exist and centralize it a bit.


I don't think it tries to support old D any more, but I just 
don't believe anyone has wanted to change it. Programmers don't 
like to remove clever indirection tricks after writing them... 
what if you think of some better way to do it later?!

Kagamin <spam here.lot> writes:

It's a strong typed handle, in C it's declared as

#ifdef STRICT
typedef void *HANDLE;
#if 0 && (_MSC_VER > 1000)
#define

#else
#define

#endif
#else
typedef PVOID HANDLE;
#define DECLARE_HANDLE(name) typedef HANDLE name
#endif

Andre Pany <andre s-e-a-p.de> writes:

On Friday, 1 February 2019 at 07:35:34 UTC, Kagamin wrote:
 It's a strong typed handle, in C it's declared as

 #ifdef STRICT
 typedef void *HANDLE;
 #if 0 && (_MSC_VER > 1000)
 #define

 #else
 #define

 #endif
 #else
 typedef PVOID HANDLE;
 #define DECLARE_HANDLE(name) typedef HANDLE name
 #endif

Thanks for all answers.
I understand, there was a reason in the past, but now
it is a superfluous construct.
I will create an issue and after that checks whether I can
create a pull request.

Kind regards
André

Andre Pany <andre s-e-a-p.de> writes:

On Friday, 1 February 2019 at 08:12:23 UTC, Andre Pany wrote:
 On Friday, 1 February 2019 at 07:35:34 UTC, Kagamin wrote:
 It's a strong typed handle, in C it's declared as

 #ifdef STRICT
 typedef void *HANDLE;
 #if 0 && (_MSC_VER > 1000)
 #define

 #else
 #define

 #endif
 #else
 typedef PVOID HANDLE;
 #define DECLARE_HANDLE(name) typedef HANDLE name
 #endif

 Thanks for all answers.
 I understand, there was a reason in the past, but now
 it is a superfluous construct.
 I will create an issue and after that checks whether I can
 create a pull request.

 Kind regards
 André

Issue created
https://issues.dlang.org/show_bug.cgi?id=19702