Annotating SortedRange.empty const: Best way to auto-deduce annotations?

[SimonN]

Hi,

About this issue in Phobos:
https://issues.dlang.org/show_bug.cgi?id=21216
SortedRange.empty should be const, .front should be inout

Just adding const/inout to SortedRange's methods won't be enough; 
if we add const/inout here, then many other Phobos ranges need to 
become const/inout-correct to keep the tests passing. Before I 
dive deeper into annotating their methods, I would like to verify 
my assumptions on how template function attribute deduction works:

1) I know that templated functions deduce their own attributes on 
instantiation. But front()/empty() are non-templated methods 
within the templated struct SortedRange. Will attribute deduction 
happen here?

2) Is it sensible/possible to force attribute deduction by 
declaring empty() in SortedRange as a zero-argument template? 
I.e.:
     @property bool empty()() { return this._input.empty; }

3) Should I rather annotate the non-templated 
SortedRange.empty/.front manually? But with what, then? empty() 
should probably be const, but it's never @nogc if annotated 
manually, even if the wrapped range offers empty() @nogc.

-- Simon