The capability you're interested in could also be achieved by simply making assignment an expression, rather than a statement, such that the value of the assignment expression is the value that was assigned. This is how C and some other C-derived languages treat it, which is why you can say things in those languages like
int x, y, z;
x = y = z = 0;
Given that Swift is syntactically like C in many ways, sometimes I've wondered why the core team opted to leave this out—maybe they feel that it's along the same lines as ++, --, and C-style for loops which were later removed, as features that aren't truly necessary and don't strictly improve the legibility of code.
It doesn't look like there's been much discussion about this on the forums that I can find, but @jrose has some interesting insight in this post about how it's not immediately obvious what the correct thing is to do when properties with possible side effects to assignment are involved.