Why do some T.init evaluate to true while others to false?

[ArturG via Digitalmars-d-learn]

On Friday, 27 May 2016 at 14:48:59 UTC, Adam D. Ruppe wrote:
> On Friday, 27 May 2016 at 14:43:47 UTC, ArturG wrote:
>>>     if(value is typeof(value).init) ...
>>
>> that still requiers a special case for floating points, arrays 
>> and optionally empty string literals.
>
> Have you tried? That should work in all cases.

does this count?

struct Foo
{
     int x;
     float f;
}

void main()
{
     Foo foo;
     if(foo is typeof(foo).init) "A: does'nt work".writeln;
     foo = Foo();
     if(foo is typeof(foo).init) "B: works".writeln;
}


if you remove the float from the struct both cases work or if you 
define the float inside the struct like this:

struct Foo
{
     int x;
     // float f = float.init; // does'nt work
     float f = float.nan;
}