D can also call C's printf, and checking that is magical indeed. It exactly follows the C99 Standard for printf. A major feature of D is being able to call C functions directly, and printf is one of them. (D doesn't recognize printf specifically, it has to have a special attribute for it `pragma(printf)` which the compiler recognizes. This is so the checking can be applied to user-defined functions that use conforming printf-style format strings.)
OK, thanks for clarifying. Reading back your original comment, I can see that its literal wording does say that. I was confused by you leading with printf handling, which is not really relevant to the original article (certainly not as much as writef()), so I inferred you were only mentioning it as context to writef() working similarly. Your use of the word "simply" also threw me off, it sounded like you thought compiler magic was a better solution that a language-level one.
I now see you were just making an unrelated point first. And having a specific compiler feature just for printf (and co.) is totally reasonable given how widespread it.
Your first link answers what would've been a follow up question: OK, writef() is a variadic template implemented with just normal language features, but does it do compile-time checking of the format? The docs says that it does:
> fmt: The format string. When passed as a compile-time argument, the string will be statically checked against the argument types passed.
https://dlang.org/phobos/std_stdio.html#.writef
D can also call C's printf, and checking that is magical indeed. It exactly follows the C99 Standard for printf. A major feature of D is being able to call C functions directly, and printf is one of them. (D doesn't recognize printf specifically, it has to have a special attribute for it `pragma(printf)` which the compiler recognizes. This is so the checking can be applied to user-defined functions that use conforming printf-style format strings.)
https://dlang.org/spec/pragma.html#printf
And the code to do it:
https://github.com/dlang/dmd/blob/master/src/dmd/chkformat.d