potential VariableView.shape fix

[kjohnsen]

I don't know if this behavior is desired, but if it is and tests pass, this seems to work.

closes #1555

[kjohnsen]

The only test that failed on my machine (WSL Ubuntu 22.04) was

E               AssertionError: Transformation for statement 'x = x + x' gave an unexpected result: RHS expressions '2.00000000000000' and '2' are not identical
E               assert 2.00000000000000 == 2

brian2/tests/test_codegen.py:488: AssertionError

[mstimberg]

Many thanks for the PR. Unfortunately, this fix would break standalone mode in some (corner-)cases. E.g. the following

>>> import brian2.only as b2
>>> b2.set_device('cpp_standalone')
>>> ng = b2.NeuronGroup(10, 'v : 1')
>>> ng.v = 'rand()'
>>> ng.v.shape
(10,)

would raise an error, since it tries to access the values of ng.v, which are not known in standalone mode before running the simulation. I will have a closer look, I am sure there is a reasonably simple solution.

[mstimberg]

@kjohnsen I committed a slight variant of the previous code (plus some tests to make sure that everything works). I am going to merge it now, but please let me know if you run into any issues.

[kjohnsen]

Groovy. Thank you!