http://www.d-programming-language.org/phobos/std_format.html#format-string %s should describe these.
https://github.com/D-Programming-Language/phobos/pull/2108
Commits pushed to master at https://github.com/D-Programming-Language/phobos https://github.com/D-Programming-Language/phobos/commit/83b9b44f461278e296a8df6f470eb460830ce8af Fix Issue 7289 - Document how std.format handles structs, unions, and hashes. https://github.com/D-Programming-Language/phobos/commit/bdb16b18b13e29f760ece2ab56b330dade63a92b Merge pull request #2108 from AndrejMitrovic/Fix7289 Issue 7289 - Document how std.format handles structs, unions, and hashes.