How can I update all Dictionary entries in place?

[Karl]

I tried to find the relevant posts, but this is the only one I could find:

In-place map for MutableCollection

It's worth noting that, with more of the ownership model fleshed out, map itself could get most of the in-place-modification optimization benefit from consuming its self argument and having the map closure consume its argument as well. This would allow a map of a uniquely-referenced value to reuse the value's buffer, possibly even while changing the type, as long as the buffer is large enough to hold the resulting array.

I'm pretty sure I've heard this from others, too, though - that we're trying to move away from having copying/mutating variants of every collection algorithm (can you imagine, like for all the String transformations? formUppercased/formLowercased/formCapitalized/etc).

I do think making the index subscript settable is a worthwhile change, though.