4 ms·

> Not necessarily, because you might consider it acceptable for the implicit conversion to change the memory layout in this sense. Does the actual data layout

• lmm 2y ago
  > If you have A, something that accepts B, and you consider it implicitly possible for an A to be a B with either no change or an implicit change... that seems to amount to considering As to be Bs when necessary. The fact that an A can be implicitly converted to a B in this context does not mean that an A should always be implicitly converted to B. (In this case B is effectively a pointer/reference to A; implicitly forming that reference is a useful convenience feature in some contexts, but I don't think treating A as a subtype of reference to A in the general case is a good idea)
  • dwattttt 2y ago
    But isn't it being implicit what makes it a subtype? It doesn't have to be a pointer; integer coercion should also be considered a form of subtyping. I don't know what to make of context here; if you're referring to whether you have a pointer to a type as context, I think it makes more sense to consider that part of the type (i.e. a pointer a A is a subtype of a pointer to B, while A is not a subtype of B)
    • lmm 2y ago
      My point is that allowing an A to implicitly convert to a pointer to A when calling a function that takes a pointer to A is reasonable, whereas always allowing that implicit conversion anywhere in your program is rather less so. The same applies to integer conversion; there are contexts in which it should maybe happen implicitly, but not everywhere.