[swift-evolution] Enhanced existential types proposal discussion

[Jan E. Schotsman]

On May 26, 2016, at 3:44 PM, Austin Zheng wrote:

> The inimitable Joe Groff provided me with an outline as to how the  
> design
> could be improved. I've taken the liberty of rewriting parts of the
> proposal to account for his advice.

Looks like great progress!

A few remarks:

1.I don't see the need for AllOf. A nested existential also acts as a  
constraint bundle, so you would have to write

Any<ProtocolA, AllOf< ProtocolB, ProtocolC>>

for consistency.

In a "is subclass of" constraint the superclass also acts as a  
constraint bundle, in a sense.

2.If openas never fails why do we need to use optional binding with it?

3. You have a typo in the "where clause" section:  where  
Collection.Element == Streamable