ICTI and ISTI

[Lars T. Kyllingstad]

IFTI -- implicit function template instantiation -- is a pretty nifty 
feature in D, which allows code that calls templated functions to be 
written in a nice, clear way.

Would it be possible to extend it to also work for class/struct 
construction, so that the type of a templated class can be deduced from 
its constructor's arguments? Here's an example of what I mean:

   class Foo(T)
   {
       T bar;
       this(T t) { bar = t; }
   }

   auto foo = new Foo(1.0);  // The type of foo is now Foo!double

I've found myself wishing for this in several cases. Sometimes the 
template specification has been so involved that I've ended up writing 
factory methods instead of ordinary constructors. But then, the classes 
in question become inconsistent with the rest of my code, and I hate 
inconsistencies.

I've only seen this mentioned once before, in bug report 1856, but none 
of the comments in that report say anything more about it.

   http://d.puremagic.com/issues/show_bug.cgi?id=1856

Are there specific reasons why ICTI and ISTI wouldn't work?

-Lars