[phobos] is*Range + Qualified Types

[David Simcha]

I'm looking to go on a major debugging spree and make std.range work 
with const ranges.  For example, the following should work:

import std.range, std.algorithm;

void main() {
     const foo = map!"a ^^ 2"([1,2,3,4,5]);
     auto myRetro = retro(foo);
}

Right now, I don't even get to the point of instantiating retro because 
I get the following encrypted Klingon related to its constraints:

test9.d(5): Error: template std.range.retro(R) if 
(isBidirectionalRange!(R)) does not match any function template declaration
test9.d(5): Error: template std.range.retro(R) if 
(isBidirectionalRange!(R)) cannot deduce template function from argument 
types !()(const(Map!(result,int[])))

This error occurs because front(), popFront(), et al. aren't callable on 
const(Map) objects.  This is pretty much a blocker for fixing the deeper 
issues.  Does it sound reasonable to everyone that is*Range, where * is 
forward, bidirectional, etc. should operate on the shallowly Unqual'd 
version of the type, or is there some good reason I'm missing why this 
shouldn't be the case?