[swift-evolution] [Draft] Abolish IUO type

[Brent Royal-Gordon]

> Let me play devil’s advocate: why not just get rid of implicit unwrapping entirely?
> 
> Apple’s Objective-C APIs have had plenty of time to be audited by now.

Two reasons:

1. There are still a number of obscure Apple frameworks which have not been audited.

2. Not all imported code comes from Apple frameworks. In particular, Linux is a whole new world of unaudited—and frankly, probably never-going-to-be-audited in large part—code. Each time Swift moves to a new platform, it will need implicit unwrapping again for a few years while the major libraries get audited. Burning your ships is only a good motivational strategy if you don't need to go anywhere else.

-- 
Brent Royal-Gordon
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