Mutable struct vs Ref in an immutable one?

[torrance]

@vchuravy

A downside is the layout when the A and B are contained in other structures. As an example inside an array A can be stored inline whereas for B a reference will be stored.

@vchuravy This touches on a question I asked some time ago about determining when a type is stored inline in an array versus as pointers.

I understood that only isbits types were stored inline, and that therefore in this case Struct A would not be stored inline.

Is this wrong? And if so (as I asked in the other thread), how can I determine when a type will be stored inline or not?