writef, compile-checked format, pointer

[Patrick Schluter]

On Monday, 9 August 2021 at 19:38:28 UTC, novice2 wrote:
> format!"fmt"() and writef!"fmt"() templates
> with compile-time checked format string
> not accept %X for pointers,
>
> but format() and writef() accept it
>
> https://run.dlang.io/is/aQ05Ux
> ```
> void main() {
>     import std.stdio: writefln;
>     int x;
>     writefln("%X", &x);  //ok
>     writefln!"%s"(&x);  //ok
>     //writefln!"%X"(&x);  //compile error
> }
> ```
>
> is this intentional?

Yes. %X is to format integers. Runtime evaluation of a format 
string does not allow for type checking. When using the template, 
the evaluation can be thorough and the types can be checked 
properly. You have 2 solutions for your problem, either a type 
cast

     writefln!"%X"(cast(size_t)&x);

or using the generic format specifier that will deduce itself the 
format to using depending in the passed type.

     writefln!"%s"(&x);