• Ilya (11/11) Nov 20 2015 Can DMD frontend optimize
• Justin Whear (10/25) Nov 20 2015 Yes this occurs as part of the constant folding I believe.
• Tofu Ninja (7/18) Nov 21 2015 If you really want to make sure it is concatenated at compile
• Marc =?UTF-8?B?U2Now7x0eg==?= (5/16) Nov 21 2015 At least for string (and array?) literals, it's now guaranteed to

Ilya <ilyayaroshenko gmail.com> writes:

Can DMD frontend optimize
  string concatenation
```
enum Double(S) = S ~ S;

assert(condition, "Text " ~ Double!"+" ~ ___FUNCTION__);
```

to

```
assert(condition, "Text ++_function_name_");

```
?

Justin Whear <justin economicmodeling.com> writes:

On Fri, 20 Nov 2015 20:39:57 +0000, Ilya wrote:

 Can DMD frontend optimize
   string concatenation
 ```
 enum Double(S) = S ~ S;
 
 assert(condition, "Text " ~ Double!"+" ~ ___FUNCTION__);
 ```
 
 to
 
 ```
 assert(condition, "Text ++_function_name_");
 
 ```
 ?

Yes this occurs as part of the constant folding I believe.

$ cat test.d
enum Double(string S) = S ~ S;
void main(string[] args){
	assert(args.length, "Text " ~ Double!"+" ~ __FUNCTION__);
}

$ dmd test.d
$ strings test | grep Text
Text ++test.main

Tofu Ninja <emmons0 purdue.edu> writes:

On Friday, 20 November 2015 at 20:39:58 UTC, Ilya wrote:
 Can DMD frontend optimize
  string concatenation
 ```
 enum Double(S) = S ~ S;

 assert(condition, "Text " ~ Double!"+" ~ ___FUNCTION__);
 ```

 to

 ```
 assert(condition, "Text ++_function_name_");

 ```
 ?

If you really want to make sure it is concatenated at compile 
time, just do this:

...

enum CT(alias S) = S;
assert(condition, CT!("Text " ~ Double!"+" ~ ___FUNCTION__)); // 
Must be evaluated at CT no matter what

Marc =?UTF-8?B?U2Now7x0eg==?= <schuetzm gmx.net> writes:

On Friday, 20 November 2015 at 20:39:58 UTC, Ilya wrote:
 Can DMD frontend optimize
  string concatenation
 ```
 enum Double(S) = S ~ S;

 assert(condition, "Text " ~ Double!"+" ~ ___FUNCTION__);
 ```

 to

 ```
 assert(condition, "Text ++_function_name_");

 ```
 ?

At least for string (and array?) literals, it's now guaranteed to 
happen at compile time. It was changed in order to get rid of the 
error-prone "concatenation by juxtaposition" feature inherited 
from C. I'm not sure it also applies to non-literals, though.