<commit_before># Abolish `ImplicitlyUnwrappedOptional` type

* Proposal: [SE-0054](0054-abolish-iuo.md)
* Author: [<NAME>](http://github.com/cwillmor)
* Review Manager: [<NAME>](https://github.com/lattner)
* Status: **Implemented (Swift 3)**
* Decision Notes: [Rationale](https://lists.swift.org/pipermail/swift-evolution-announce/2016-March/000084.html)
* Implementation: [apple/swift#2322](https://github.com/apple/swift/pull/2322)

## Introduction

This proposal seeks to remove the `ImplicitlyUnwrappedOptional` type from the
Swift type system and replace it with an IUO attribute on declarations.
Appending `!` to the type of a Swift declaration will give it optional type and
annotate the declaration with an attribute stating that it may be implicitly
unwrapped when used.<commit_msg>Update SE-0054 to indicate when it was fully implemented. (#835)<commit_after># Abolish `ImplicitlyUnwrappedOptional` type

* Proposal: [SE-0054](0054-abolish-iuo.md)
* Author: [<NAME>](http://github.com/cwillmor)
* Review Manager: [<NAME>](https://github.com/lattner)
* Status: **Implemented (Swift 4.2)**
* Decision Notes: [Rationale](https://lists.swift.org/pipermail/swift-evolution-announce/2016-March/000084.html)
* Implementation: [apple/swift#14299](https://github.com/apple/swift/pull/14299)

## Introduction

This proposal seeks to remove the `ImplicitlyUnwrappedOptional` type from the
Swift type system and replace it with an IUO attribute on declarations.
Appending `!` to the type of a Swift declaration will give it optional type and
annotate the declaration with an attribute stating that it may be implicitly
unwrapped when used.
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