Raise explicitly on Python methods that are incompatible with lazy variables

[ricardoV94]

Notably changes the behavior of __bool__ to always raise. Before there was a hack based on whether a variable had been compared to something before.

This should avoid surprising behavior such as:

import pytensor.tensor as pt
x = pt.zeros(())
if x:
  print("Variable is nonzero!")  # Always triggered
else:
  print("Variable is zero")  # Never triggered

After this PR it raises

TypeError: TensorVariable cannot be converted to Python boolean. Call `.astype(bool)` for the symbolic equivalent.

The correct behavior as per the API standard is to raise in these cases: https://data-apis.org/array-api/latest/design_topics/lazy_eager.html

There is still surprising behavior with (in)equality checks, but we can't do anything about those as they are needed for Python hashing behavior. The default is x == y: True if x is y else False

import pytensor.tensor as pt
x = pt.zeros(())
if x == 0:
  print("Variable is zero!")  # Only triggered when x == x
else:
  print("Variable is nonzero")  # Always triggered

Related to #1189

---

📚 Documentation preview 📚: https://pytensor--1190.org.readthedocs.build/en/1190/

[codecov]

Codecov Report

Attention: Patch coverage is 82.53968% with 11 lines in your changes missing coverage. Please review.

Project coverage is 81.99%. Comparing base (3cdcfde) to head (04a6785).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
pytensor/scalar/basic.py	50.00%	5 Missing ⚠️
pytensor/tensor/variable.py	78.57%	3 Missing ⚠️
pytensor/compile/nanguardmode.py	0.00%	0 Missing and 1 partial ⚠️
pytensor/tensor/rewriting/math.py	80.00%	0 Missing and 1 partial ⚠️
pytensor/tensor/rewriting/subtensor.py	0.00%	0 Missing and 1 partial ⚠️

❌ Your patch status has failed because the patch coverage (82.53%) is below the target coverage (100.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1190      +/-   ##
==========================================
- Coverage   82.01%   81.99%   -0.02%     
==========================================
  Files         188      188              
  Lines       48561    48566       +5     
  Branches     8679     8677       -2     
==========================================
- Hits        39826    39823       -3     
- Misses       6572     6580       +8     
  Partials     2163     2163              

Files with missing lines	Coverage Δ
pytensor/compile/function/pfunc.py	82.92% <100.00%> (ø)
pytensor/compile/function/types.py	80.66% <100.00%> (ø)
pytensor/scalar/loop.py	90.12% <100.00%> (ø)
pytensor/scalar/math.py	87.76% <100.00%> (ø)
pytensor/scan/basic.py	83.91% <100.00%> (ø)
pytensor/tensor/basic.py	91.36% <100.00%> (-0.02%)	⬇️
pytensor/tensor/conv/abstract_conv.py	76.07% <100.00%> (ø)
pytensor/tensor/math.py	92.01% <100.00%> (ø)
pytensor/tensor/rewriting/blas.py	89.64% <100.00%> (ø)
pytensor/tensor/rewriting/special.py	82.35% <100.00%> (ø)
... and 5 more

[Armavica]

I think you can remove lines 779:783 of pytensor/scalar/basic.py, otherwise that looks good to me

[ricardoV94]

I think you can remove lines 779:783 of pytensor/scalar/basic.py, otherwise that looks good to me

Thanks, removed them