Bug 10571 – formattedWrite error with delegate and string

I can't format a string into a delegate taking a 'const char[]'. This seems wrong to me. ---------------------------------- import std.format; void main() { string buf; formattedWrite((in char[] s) { buf ~= s; }, "%s", "hello"); assert(buf == "hello"); } ---------------------------------- DMD v2.064 DEBUG F:\documents\desktop\d\sourcecode\phobos\std\range.d(611): Error: static assert "Cannot put a dchar into a void delegate(const(char[])) nothrow @safe" F:\documents\desktop\d\sourcecode\phobos\std\format.d(1752): instantiated from here: put!(void delegate(const(char[])) nothrow @safe, dchar) F:\documents\desktop\d\sourcecode\phobos\std\format.d(2146): instantiated from here: formatValue!(void delegate(const(char[])) nothrow @safe, dchar, char) F:\documents\desktop\d\sourcecode\phobos\std\format.d(1790): instantiated from here: formatRange!(void delegate(const(char[])) nothrow @safe, string, char) F:\documents\desktop\d\sourcecode\phobos\std\format.d(2996): ... (1 instantiations, -v to show) ... F:\documents\desktop\d\sourcecode\phobos\std\format.d(420): instantiatedfrom here: formatGeneric!(void delegate(const(char[])) nothrow @safe, string, char) testx.d(7): instantiated from here: formattedWrite!(void delegate(const(char[]) s) nothrow @safe, char, string)

*** This issue has been marked as a duplicate of issue 9823 ***

Ok, maybe not.

(In reply to comment #0) > I can't format a string into a delegate taking a 'const char[]'. This seems > wrong to me. > > ---------------------------------- > > import std.format; > > void main() > { > string buf; > formattedWrite((in char[] s) { buf ~= s; }, "%s", "hello"); > assert(buf == "hello"); > } > > ---------------------------------- Yup. The branches char/string don't work with a delegate sink that accepts a const(char)[]. Here is a somewhat reduced case. //---- import std.format; void main() { FormatSpec!char f; formatValue((const(char)[]){}, '本', f); formatValue((const(char)[]){}, "a", f); } //---- The root issue is that "formatValue" for wide characters doesn't actually work. It just calls "put" and hopes put will magically do the work :D formatValue for strings then also fails, because it has to compile the "%r" path (raw), which iterates over the string as a range (dchars), and then prints these raw with formatValue(dchar), which, again, doesn't work. The reason we haven't seen this failure in the testers yet, is that std.format is mostly unittest using Appender, and Appender *knows* how to transcode, making it a very poor choice for thorough testing. In any case, this gets fixed by my "put" fix: https://github.com/D-Programming-Language/phobos/pull/1439

Commit pushed to master at https://github.com/D-Programming-Language/phobos https://github.com/D-Programming-Language/phobos/commit/156962217c1e79ebfe02eb673e00cdff1685bd4f Issue 10571 - formattedWrite error with delegate and string

Yay!