Force variables to be different in @varnames_interface

[lgoettgens]

Resolves #1761.

Do we consider this a breaking change to AA?

cc @mgkurtz

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.15%. Comparing base (c8aec15) to head (3b8beb0).
Report is 4 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1850   +/-   ##
=======================================
  Coverage   88.15%   88.15%           
=======================================
  Files         119      119           
  Lines       30017    30052   +35     
=======================================
+ Hits        26460    26493   +33     
- Misses       3557     3559    +2     

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[fingolfin]

Of course it may break some existing code. But OscarCI is green. So personally I'd be fine declaring the use of multiple variables with identical names a "bug" and so this a fix.

We can talk about it during triage...

[lgoettgens]

@fingolfin and @wdecker will look at some intersection theory examples

[fingolfin]

(I deleted this comment here and instead reposted it on issue #1761 to keep the discussion there. But in a nutshell I don't think we should go with this as it is)

[fingolfin]

See discussion on issue #1761