I would like to propose a change to the default access modifier within an
enclosing scope. The default for top level definitions would stay internal,
but anything within a scope would by default have the same visibility as it’s
enclosing scope.
The main reason for this is readability/maintainability, and having the
intention clearly stand out. It would also reduce a great amount of
boilerplate. It also matches the mental model of how scopes normally work
regarding inheritance of visibility/properties (which means less to teach
newbies).
Right now if I want to make a type and all of it’s vars/methods public, I have
to mark each individual var/method public, which leads to a lot of
boilerplate/noise and makes everything harder to read:
public struct MyStruct {
public var a:Int
public var b:Int
private var c:Int
public var d:Int
}
Notice that the private var doesn’t really stand out as such very well. Also,
it is exceedingly rare (at least in my own coding style) that I actually want
an internal variable unless the type itself is internal, and in those cases, I
would like that choice to stand out as deliberate the same way I want ‘private'
to stand out. As it stands, I wait until I think I am done modifying a type to
mark it public because of the extra noise generated. I also make a point to
write ‘internal' for things that I explicitly want to restrict to internal.
Consider the alternative:
public struct MyStruct {
var a:Int
var b:Int
private var c:Int
var d:Int
}
Now the fact that I have chosen to make ‘c’ private really stands out much
better. When revisiting the code in 6 months, the struct is much more
“glance-able” (as a friend of mine likes to say).
Note also the nuance that I didn’t say that those vars were marked public (or
had the same modifier), I said that they had the SAME VISIBILITY as the
enclosing scope (which in this case happens to be public). This is a concept
which is hard to express currently, and IIRC this is what we had to do to make
the edge cases of swift 3’s private modifier work properly.
Basically, it already works this way for ‘private’, ‘fileprivate’, &
‘internal’, just not for ‘public’ or ‘open’… which can be surprising,
especially since you don’t discover these differences until you are working
across modules. We should just extend that mental model up to include public
and open. Migration would just take internal variables of public/open types
and mark them explicitly with the word ‘internal'.
Thanks,
Jon
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