Bug 18101 – allow Tuple for BetterC

=============== code =============== import std.typecons : Tuple; alias BOMSeq = Tuple!(int, "schema"); extern(C) int main(){ return 0; } ========================= ../src/phobos/std/range/primitives.d(405): Error: static assert "Cannot put a const(char)[] into a Appender!string." ../../src/phobos/std/format.d(1172): instantiated from here: put!(Appender!string, const(char)[]) ./../src/phobos/std/format.d(473): instantiated from here: writeUpToNextSpec!(Appender!string) ../../src/phobos/std/format.d(5831): instantiated from here: formattedWrite!(Appender!string, char, ulong, ulong) ../../src/phobos/std/typecons.d(542): instantiated from here: format!(char, ulong, ulong) test.d(4): instantiated from here: Tuple!(int, "schema")

The error has been fixed in I opened a PR to add a betterC testsuite to Phobos https://github.com/dlang/phobos/pull/5952, but it still doesn't look like it can work.

Works for current HEAD