Bug 8473 – Guaranteed relative key-values with byKey and byValue

This is a spinoff of Issue 5466 There is a common need to have a (lazy) range of keys and their corresponding values of an associative array. Sometimes iterating them in parallel with a foreach is not enough, and performing a lookup for each key generated by byKeys is not efficient. So I suggest to state in the D docs that if the associative array is not modified in the iteration, its byKey and byValue yield corresponding key-values (this is currently true, but not guaranteed to be true in all D implementations). This means that this will always be true in all future D implementations: zip(aa.byKey, aa.byValue) === aa.byPair

There is now a byKeyValue: https://github.com/D-Programming-Language/druntime/pull/1070