Style/RedundantSelf creates false positive with parallel assignment

[daniel-rikowski]

When using parallel assignment involving self Style/RedundantSelf thinks self is redundant.
Expanding the parallel assignment works, i.e. self is recognized as non-redundant:

With parallel assignment:

old_log_level, self.log_level = log_level, :fatal  # Redundant `self` detected

Serial assignment:

old_log_level = log_level
self.log_level = :fatal # No redundant `self` detected

---

Expected behavior

Rubocop should notice that self is not redundant.

Actual behavior

Rubocop thinks that self is redundant.

Steps to reproduce the problem

Check this code with Style/RedundantSelf enabled:

def parallel
  old_log_level, self.log_level = log_level, :fatal
end

def serial
  old_log_level = log_level
  self.log_level = :fatal
end

RuboCop version

$ rubocop -V
0.48.0 (using Parser 2.4.0.0, running on ruby 2.3.3 i386-mingw32)

[bbatsov]

Looks like a bug indeed.