Figure out the constructor story about subspace HOT 5 CLOSED

std::convertible_to still is used for templated function parameters in place of std::same_as.

We could provide our own version of the concept but it's not clear if that would add value, if it would check anything extra or the name could make things more clear.

It's only needed for templated function parameters since they don't convert automatically, and this makes them simply act like a normal function's parameter. I don't think we need to do a bunch of weird things just to make templated function parameters act differently, or act the same in a different way.

from subspace.

#164 addresses the points here.

1. Done: We have Default as a concept and it's just about default constructors. with_default() have all been removed.
2. Was already done. We have Copy and Move as concepts.
3. Was already done. We use constructor methods instead of constructors when there are any arguments to them (other than copy/move).
4. Done: We implemented SameOrSubclassOf to help with pointer upcast relationships, and we removed all is_convertible and is_constructible for that.

We are left with std::convertible_to concept which we use to make templated function parameters behave normally.

from subspace.

Lastly, to deal with the sad lack of CTAD with constructor methods (3), we are adding free function constructor shorthands that make a Marker type holding the arguments as references, and which can be used to construct the type.

Examples:

• sus::option::some(x) -> SomeMarker { x }
• sus::option::none() -> NoneMarker
• sus::result::ok(x) -> OkMarker { x }
• sus::result::err(x) -> ErrMarker { x }

We should also add some for other types like:

• sus::containers::array()
• sus::containers::vec()
• sus::tuple::tuple()
• sus::union_type::union... oh no. Maybe we should rename to choice if it will make this nicer. Let's see if this helper function can even exist and be useful, it should be able to... with a template param for the tag value.

Currently these are implemented by adding constructors to the types, but it should work to use operators that call the public constructors?

from subspace.

Ok, now we have the Marker types construct through the public APIs of the types instead of polluting those APIs with constructors from Markers.

Remaining to do here is add some more constructor functions + Marker types as per #125 (comment).

from subspace.

sus::union_type::union... oh no. Maybe we should #127 if it will make this nicer. Let's see if this helper function can even exist and be useful, it should be able to... with a template param for the tag value.

Ok well the function is writable and is useful: 090435e So I guess we should do the rename.

from subspace.