fix(cpp1): account for initializers of members lowered as bases

[JohelEGP]

Resolves #422.

Testing summary.

100% tests passed, 0 tests failed out of 704

Total Test time (real) = 104.69 sec

Acknowledgements.

• Tested thanks to https://github.com/modern-cmake/cppfront.
• The commit message uses Conventional Commits 1.0.0.

[JohelEGP]

With commit 379ae03,
a @struct lowers to an aggregate.
If an @struct type also has members lowered as bases,
it's necessary to continue emitting those SMFs.
-- #422 (comment)

[JohelEGP]

I suppose the only reasonable option is to queue an error if emitting SMFs is suppressed.

I can't reliably lower an initializer to the *_as_base's data member's initializer,
as it could only be valid in the derived type's scope
(e.g., uses the type's template parameter or a previous data member).

I thought about also emitting actual bases to *_as_struct_base,
but besides being equally problematic to move the lowered initializer,
the change from a direct base class to an indirect one should come with its own set of problems.

I wonder if the error falls under the banner of "(temporary alpha limitation)".

[hsutter]

Hi! Sorry it took me so long to get to this one... this one looks like it might be out of date, should I close it for now and you can reopen this or create a new PR when it's ready? Again, my apologies for not keeping up.