Dealing with type information loss in Parameters Fields and Return type

[Jonathan M Davis via Digitalmars-d-learn]

On Sunday, April 17, 2016 10:12:29 Nicholas Wilson via Digitalmars-d-learn 
wrote:
> So currently there is a loss of information when Parameters
> Fields and Return type.
> i.e. assuming 64 bits
> size_t foo(ptrdiff_t) {};
>
> writeln(ReturnType!foo); // prints ulong
>
> Is there any way to get the types as (tuples of) strings of the
> the types as they are in the source file?
>
> auto foos = StringReturnType!foo;
> static assert(typeof(foos) == string);
> pramga(msg, foos); // available at CT, prints size_t

I'm actually surprised that you got the compiler to give you size_t in any
form. size_t is simply an alias to either ulong (on 64-bit systems) or uint
(on 32-bit systems), and for better or worse, aliases pretty much just
disappear. As far as the compiler is concerned, if it sees

alias size_t = ulong;

t's basically just replacing all instances of size_t with ulong, and size_t
doesn't even exist. The same goes with any other alias (like ptrdiff_t)
whether you declare it or whether it's in druntime or Phobos. You will never
see size_t in an error message except maybe when you mistype it, and the
compiler is providing a suggestion for what you meant to type. As far as
the compiler is concerned, there is no difference between an alias and what
it's an alias of.

- Jonathan M Davis