[FIX #4196] Rails/RelativeDate constant complains on lambda and proc

[smakagon]

Fixes the following case for Rails/RelativeDate cop:

CONST = -> { 1.year.ago }

Before this fix it would show:

bug.rb:1:1: C: Rails/RelativeDateConstant: Do not assign ago to constants as it will be evaluated only once.
CONST = -> { 1.year.ago }

As reported here.

[bbatsov]

Please, use node destructuring here (e.g. something like _scope, const_name, value = *node) instead of accessing node.children directly. I don't like this, because it gives 0 indication what exactly are you checking when you flatten the nodes to an array.

[bbatsov]

Btw, it seems to me you can return quickly for anything but a send node on the right-hand side of the assignment. Obviously - if it's not a send it can't be what this cop is checking for.

Overall this cop is implemented in a rather odd manner and can benefit from using node patterns IMO.

[bbatsov]

I'll merge this because I want to cut a release and I'll fix it myself.

[bbatsov]

Looking more closely in the code - this part bad_node = node.descendants.find { |n| bad_method?(n) } makes no sense to me. We should simply be inspecting whatever's the rhs on this assignment. @smakagon I'd appreciate it if you can take a look at improving this code when you have some time.

[smakagon]

@bbatsov sure, I'll try to refactor that cop and add more specs.