(feature suggestion) tuple destructuring and ellipsis: `(a, b...) = function()`

[plut]

All is in the title. Currently this syntax is not understood:

julia> (head, tail...) = (1,2,3,4,)

ERROR: syntax: invalid assignment location "b..." around REPL[1]:1

This would probably be quite easy to implement (just replace rvalue[2] by rvalue[2:end] whenever there is an ellipsis), very natural to understand, and does not overwrite any existing syntax. It also provides a nice way of dealing with lists (LISP-style).

Also, while I'm writing about tuples, this is a bit surprising:

julia> (head, tail) = (1,2,3,4,)
(1,2,3,4)
julia> (head, tail)
(1,2)

I would argue that there is at least a missed warning here (in the first line, while I understand that this is lowered as head=(1,2,3,4)[1]; tail=(1,2,3,4)[2], it should warn that the lvalue tuple is too short), and some strange behavior of the assignment operator (it is very weird that an expression of the form A=B does not return the value of A).

[fredrikekre]

Implemented in #37410 on master (edit: actually in 1.6 too!):

julia> (head, tail...) = (1, 2, 3, 4)
(1, 2, 3, 4)

julia> head
1

julia> tail
(2, 3, 4)