Can someone please explain why the following assertion fails?

[Ali Çehreli via Digitalmars-d-learn]

On 10/31/2016 12:08 PM, Gary Willoughby wrote:
> Can someone please explain why the following assertion fails?
>
> import std.stdio;
> import std.conv;
>
> void main(string[] args)
> {
>     auto x = 1;
>
>     assert(hashOf(x.to!(string)) == hashOf(x.to!(string)));
> }
>
> Thanks.

Because it considers the .ptr property of arrays as well:

 
https://github.com/dlang/druntime/blob/master/src/core/internal/hash.d#L61

//dynamic array hash
size_t hashOf(T)(auto ref T val, size_t seed = 0)
if (!is(T == enum) && !is(T : typeof(null)) && is(T S: S[]) && 
!__traits(isStaticArray, T)
     && !is(T == struct) && !is(T == class) && !is(T == union))
{
     alias ElementType = typeof(val[0]);
     static if (is(ElementType == interface) || is(ElementType == class) ||
                    ((is(ElementType == struct) || is(ElementType == union))
                        && is(typeof(val[0].toHash()) == size_t)))
     //class or interface array or struct array with toHash(); CTFE 
depend on toHash() method
     {
         size_t hash = seed;
         foreach (o; val)
         {
             hash = hashOf(o, hash);
         }
         return hash;
     }
     else static if (is(typeof(toUbyte(val)) == const(ubyte)[]))
     //ubyteble array (arithmetic types and structs without toHash) CTFE 
ready for arithmetic types and structs without reference fields
     {
         auto bytes = toUbyte(val);
         return bytesHash(bytes.ptr, bytes.length, seed);    // <-- HERE
     }
     else //Other types. CTFE unsupported
     {
         assert(!__ctfe, "unable to compute hash of "~T.stringof);
         return bytesHash(val.ptr, ElementType.sizeof*val.length, seed);
     }
}

Ali