map won't actually compute anything until you start asking for individual elements with front, back, or opIndex.
Personally I like to use something like
ref transform (alias action, R, T...)(ref R range, T addl_args)
{
range = action (range, addl_args);
return range;
}
to do mutation in the middle of UFCS chains. Its more flexible
and more obvious than an impure map.
range.callchain.array.transform!(x =>
x.map!whatever).filter.etc
