type stability of left division

[araujoms]

Closes #930

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.90%. Comparing base (52c41f7) to head (86bc9c9).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1475      +/-   ##
==========================================
- Coverage   93.90%   93.90%   -0.01%     
==========================================
  Files          34       34              
  Lines       15930    15937       +7     
==========================================
+ Hits        14959    14965       +6     
- Misses        971      972       +1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[ViralBShah]

I assume that the _lucopy and copy_similar will not make copies in the cases where there is no need to promote the type. It appears to be the case on a quick look - but just want to make sure.

[araujoms]

Sorry, no, they always copy. I'm just reusing the implementations of lu and qr, so I'm not making any more copies than before, though.

[araujoms]

I've also fixed the specialized vector methods, because even though they were not type unstable they were returning an answer of the incorrect type. Luckily this involved less copying, not more.

[ViralBShah]

Good to merge?

[araujoms]

If you're asking me, yes, I think so.