On Wednesday, 14 June 2017 at 19:22:24 UTC, Steven Schveighoffer
wrote:
For example:
foreach(i, v; hashmap) => i is counter, v is value
Later hashmap adds support for iterating key and value. Now i
is key, v is value. Code means something completely different.
If we take a step back, I think we are discussing the
generalization of foreach. Let's assume we want to preserve the
current foreach behavior where associative types iterate with key
and value pairs. If the "hashmap" in your example was supposed to
be an associative type then `i` wasn't a counter, it was the key
already. If "hashmap" didn't define the iteration key (using a
new kind of opApply or whatever) then it wasn't an associative
type, and therefore your change wouldn't be valid.
So, we just have to be careful that when foreach(i, v; foo) is
introduced the relevant types in phobos also implement the new
behavior, so that this situation doesn't arise afterwards..
