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

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

to

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

```
?

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

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

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.