fixed_function is not that "fixed" sometimes

[Vuhdo]

Sometimes fixed_function actually allocates memory and that is quite unexpected and confusing.

The problem is due to alignment: when one of a captured lambda arguments has an alignment, instead of an in-place allocation it can allocate on the heap.

Here's more or less minimal example that I hope demonstrates the problem: https://godbolt.org/z/M6d4GrK3v
Here AlignedVec is aligned by 16 bytes, which makes the lambda capturing it also aligned and this does not pass the is_functor_inplace_allocatable check. And that one leads to a heap allocation.

My C++ template knowledge fails me here. Is there a way I could force fixed_function to use the inplace storage with aligned lambda captures? It would be really cool to make the class just work with any kind of aligned arguments.