Simple as that, suppose
uint[uint] aa;
Any range supports carrying an index. Not so does the Range
returned by byKey and byValue.
foreach (i, k; aa.byKey) { }
and
foreach (i, v; aa.byValue) { }
both don't compile.
Reason (I found out by chance):
If the key or value type is a std.typecons.Tuple, iteration over
aa.by* decomposes the Tuple if there is the right number of
arguments. For 2-Tuples, there cannot be both possible.
alias Tup = Tuple!(int, int);
int[Tup] it;
Tup[int] ti;
foreach (x, y; it.byKey) { }
foreach (x, y; ti.byValue) { }
Why is this undocumented? http://dlang.org/spec/hash-map.html
doesn't mention Tuples at all!
Why is this useful? Anyone can decompose the Tuple with .expand
if they like. I would prefer allowing an index.
If it does not meet the spec, is it a bug then?
