[FIX] Variable: Fix cases when equal variables had different hashes

[janezd]

Issue

May fix #4766 (comment) from #4766.

Description of changes

__hash__ did not follow the same logic as __eq__. __eq__ backtracked through identities while __hash__ (kind of) made a single step.

I replaced the recursion in __eq__ with a loop. I believe the new version to be equivalent to the old one. The old one exited earlier if compute_value's matched, but with the same result as the new one.

__hash__ then uses the same pieces of data as __eq__.

Includes

• Code changes
• Tests

[codecov]

Codecov Report

Merging #4843 into master will decrease coverage by 0.02%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #4843      +/-   ##
==========================================
- Coverage   84.12%   84.10%   -0.03%     
==========================================
  Files         282      277       -5     
  Lines       57327    56498     -829     
==========================================
- Hits        48229    47520     -709     
+ Misses       9098     8978     -120