toChars buffer access?

[Steven Schveighoffer]

I was about to reach for core.internal.string.signedToTempString [1] to 
convert a number into a temp string yet again. And I thought, maybe 
there's something in Phobos by now.

And lo and behold! There's std.conv.toChars [2]

But... it just gives me a range of char, and not an actual string. So my 
intended purpose (to use it as a string key for an associative array) 
means I have to copy it to a local buffer anyway.

No matter, right? It probably just stores the number and gives me access 
to each character as it parses. Oh wait, no. It actually stores it as a 
char[20], but doesn't give me access.

Which leaves me with the only option of doing:

auto s = someNumber.toChars;
char[20] buf;
import std.algorithm : copy;
copy(s.save, buf[0 .. s.length]);

auto v = aa[buf[0 .. s.length]];

But my goodness, it would just be so easy if it gave access to the buffer:

auto s = someNumber.toChars;
auto v = aa[s.data]; // @system access to buffer, unsafe!

And this is discounting the fact that I not only am copying the buffer 
*again*, but doing it one character at a time.

So would it be a problem to allow this accessor, even if it's @system? 
Or should I just keep importing core.internal?

-Steve

[1] 
https://github.com/dlang/druntime/blob/9f0f6e49fb379841c7934b6049f87dab0adfe53c/src/core/internal/string.d#L113

[2] https://dlang.org/phobos/std_conv.html#toChars