What other than a pointer can be converted implicitly to const(char)*?

[Steven Schveighoffer via Digitalmars-d-learn]

On 12/21/15 3:47 PM, anonymous wrote:
> On 21.12.2015 21:20, Steven Schveighoffer wrote:
>> This seems like an incorrect feature then. Why wouldn't I want S to be
>> treated like any other const(char)*? Seems like it's explicitly saying
>> "treat this like a const(char)*"
>
> To my understanding, `alias this` means "is implicitly convertible to
> X", and not "is the same thing as X".
>
> That is, `is(S == const(char)*)` is false, but `is(S : const(char)*)` is
> true. It makes sense to me that isPointer behaves like the `==` variant.
>
> And for sure, the `alias this` doesn't make S interchangeable with a
> pointer. S may have a different size, the pointer may not be at a zero
> offset in S, etc.

I'm not saying that isPointer should return true, I'm saying that it 
shouldn't be used here.

> For the phobos code in question it comes down to what's less surprising,
> I guess. Having such an `alias this` resolved before stringification, or
> not. I'm not sure.

I think the issue here is the way the code determines it should use 
std.format. My preference is:

1. if the struct defines toString, then use std.format which will call that.
2. else if the struct aliases itself to some other type handled here, 
use that branch
3. else, use std.format anyway, and whatever happens happens.

-Steve