[swift-users] Compiler fLag to activate SE-0143 (conditional conformance)?

[torquato]

SE-0143 has been accepted, but is not activated by default in the last 
builds. As per Snapshot 2017-12-06 I get the Error message: "Conditional 
conformance of 'Array<Element>' to 'Foo' depends on an experimental 
feature (SE-0143)".
Somewhere on the dev list archives I've read about a compiler flag that 
activates this feature. I can't find it anymore. Bad Google-Fu.

Questions:

1.)
What is this compiler flag?

2.)
Shouldn't this (flag) be mentioned in the proposal? Or the Generics 
Manifesto? Somewhere? At least for the meantime…?

3.)
What is the _real_ status of this proposal? Is it really accepted and 
going into a next release or is this just a tryout that can be dropped 
any time?