Shopify
Add rule against memoizing possibly falsely values
This adds a rule elaborating on some of the pitfalls of ||=.
"Avoid using ||= to initialize boolean variables" provides a good explanation about false not being safe to use with ||=, but cases where the value can be nil (e.g. not found) should also be considered.
Follow up to discussion in https://github.com/Shopify/ruby-style-guide/pull/193/files#r490432383
Agreed with @rafaelfranca. Since this was inspired by the existing rule about using ||= to assign boolean values to variables, we may need to rephrase the existing rule better in order to avoid confusion. In any case I don't think we can (or should) put restrictions about using ||= with nil. I don't see any stylistic problems erupting from that use.
