Throw error for add_to_expression with GenericNonlinearExpr

[odow]

Closes #3505

We can always revisit this in future if more people ask for it.

[codecov]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (beb1826) 98.14% compared to head (24675c0) 98.14%.
Report is 2 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #3506   +/-   ##
=======================================
  Coverage   98.14%   98.14%           
=======================================
  Files          37       37           
  Lines        5545     5547    +2     
=======================================
+ Hits         5442     5444    +2     
  Misses        103      103           

Files Changed	Coverage Δ
src/nlp_expr.jl	99.52% <100.00%> (+<0.01%)	⬆️

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[blegat]

Maybe redirect to MA.add_mul!! ?

[odow]

I don't think we can redirect to add_mul!! because add_to_expression! is in-place only.

[hdavid16]

That works. add_mul!! is behind the internal _MA in JuMP. So would the user need to load MA separately from JuMP?

[odow]

So would the user need to load MA separately from JuMP?

Yes

[blegat]

I meant redirecting in the error message

[odow]

Done