Make comparison of polynomials error if parent check fails

[joschmitt]

One way to resolve oscar-system/Oscar.jl#4107 . Let's see what CI says.

[codecov]

Codecov Report

Attention: Patch coverage is 66.66667% with 4 lines in your changes missing coverage. Please review.

Project coverage is 88.13%. Comparing base (63d54c2) to head (58323e7).
Report is 7 commits behind head on master.

Files with missing lines	Patch %	Lines
src/MPoly.jl	0.00%	2 Missing ⚠️
src/generic/MPoly.jl	66.66%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1800      +/-   ##
==========================================
- Coverage   88.14%   88.13%   -0.01%     
==========================================
  Files         119      119              
  Lines       29986    29981       -5     
==========================================
- Hits        26430    26424       -6     
- Misses       3556     3557       +1     

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[fingolfin]

I am fine with this in principle, although I am not sure how useful it is in general. But there definitely is no harm.

[joschmitt]

I am not sure how useful it is in general

To me, it sounds reasonable to throw an error if a comparison does (mathematically) not make sense instead of just saying false. I probably don't see all the consequences of this statement and we certainly couldn't enforce this consistently in OSCAR though.

[lgoettgens]

I am just artificially blocking this in favor of concluding in triage how to proceed with oscar-system/Oscar.jl#4107 first.

[lgoettgens]

I would prefer to just implement ==(::AbstractAlgebra.SetElem, ::AbstractAlgebra.SetElem) = error("== is not implemented for the given types") if we wanna have this

[lgoettgens]

I would prefer to just implement ==(::AbstractAlgebra.SetElem, ::AbstractAlgebra.SetElem) = error("== is not implemented for the given types") if we wanna have this

Triage agreed with this idea