Template type deduction and specialization

[Jonathan M Davis via Digitalmars-d-learn]

On Wednesday, May 20, 2015 07:36:21 Namespace via Digitalmars-d-learn wrote:
> What about:
> ----
> import std.stdio;
>
> void printVal(T)(T t) {
>      static if (is(T : U*, U))
>          printVal(*t);
>      else
>          writeln(t);
> }
>
> void main() {
>      int x = 100;
>      printVal(x);
>      int* px = &x;
>      printVal(px);
> }
> ----

That mostly works, but you it runs the classic risk of running into problems
with alias this (which is why checking for implicit conversions in static if
or template constraints is so incredibly dangerous if you're not _very_
careful). std.traits defines isPointer as follows:

enum bool isPointer(T) = is(T == U*, U) && !isAggregateType!T;

which avoids the alias this problem. Regardless, it's more idiomatic to just
use isPointer.

- Jonathan M Davis