Introducing role keywords to reduce hard-to-find bugs

[Tino]

@QuinceyMorris

Has there been any discussion of enhancing the language to explicitly recognize a “consumption protocol” (i.e. a set of behaviors that clients of the protocol can assume to exist) and “production protocol” (i.e. a set of requirements on what conformers to the protocol must bring to the party).

I'm not aware of such discussion — but people not being aware of important other posts is one major problem here ;-)
Pure "consumption protocols" are imho an odd thing, so I can't think of any benefit a split would have.

But to refine that classification, I see two motivations for default implementations:
Making methods optional, and functions build on top of other parts of the protocol.

@QuinceyMorris

Firstly, I’m a bit horrified by the snowdrifts of modifiers that are building up at the start of declarations

Looks like we have similar feelings ;-)

Default implementations in protocol declarations

Self-fullfilling prophecy: Why do server side projects seem to reinvent everything? - #8 by Tino ;-) My perspective is that role keywords are quite a big change which pushes Swift into the direction of "public final static void main", whereas the alternatives are not only more powerful, but also simpler ¯\(ツ)/¯