[swift-evolution] End of source-breaking changes for Swift 3

Brian Gesiak modocache at gmail.com
Thu Jul 28 10:30:08 CDT 2016

Apologies if this was announced elsewhere: is commit access to master

I noticed I couldn't merge some documentation improvements in
https://github.com/apple/swift/pull/3815, and just wanted to make sure this
was due to Swift 3 finalization.

If commit access is restricted, is it safe to assume that restriction will
be lifted on or around July 29?

- Brian Gesiak

On Thu, Jul 28, 2016 at 7:15 AM, Anton Zhilin via swift-evolution <
swift-evolution at swift.org> wrote:

> https://github.com/apple/swift/commit/c8c41b385c0312e562abe4952fa2d6794dec2e0f
> Is SE-0077 going to be implemented for Swift 3?
> https://github.com/apple/swift/blob/master/stdlib/internal/SwiftExperimental/SwiftExperimental.swift
> Does this code actually run?
> If so, I will add "implemented" to the proposal, plus I still haven't
> added latest naming changes. ¯\_(ツ)_/¯
> 2016-07-28 1:17 GMT+03:00 Tony Allevato via swift-evolution <
> swift-evolution at swift.org>:
>> I noticed that while SE-0091 appears to be implemented (from a cursory
>> glance at some of the affected types like Equatable and String), it looks
>> like the named methods are still part of the FloatingPoint protocol and
>> they still use global operators.
>> Is anyone tracking the migration of that protocol (and possibly also the
>> new Integer protocols) to use the new operator technique? (I have to
>> apologize for not being able to update the proposal with another PR that
>> listed all those changes—my free time outside my day job has been
>> significantly reduced lately.)
>> On Wed, Jul 27, 2016 at 12:38 PM Ted Kremenek via swift-evolution <
>> swift-evolution at swift.org> wrote:
>>> Dear friends,
>>> Today is July 27 — and the last planned day to take source-breaking
>>> changes for Swift 3. It has been an incredible ride to this point, so let's
>>> take stock of where we are. Here are the list of currently accepted — but
>>> not yet (fully) implemented — evolution proposals (this is drawn from the
>>> "accepted" but not marked "implemented" proposals from the
>>> swift-evolution <https://github.com/apple/swift-evolution> repository):
>>>    - SE-0025 - Scoped Access Level
>>>    <https://github.com/apple/swift-evolution/blob/master/proposals/0025-scoped-access-level.md>
>>>    - SE-0042 - Flattening the function type of unapplied method
>>>    references
>>>    <https://github.com/apple/swift-evolution/blob/master/proposals/0042-flatten-method-types.md>
>>>    - SE-0045 - Add scan, prefix(while:), drop(while:), and iterate to
>>>    the stdlib
>>>    <https://github.com/apple/swift-evolution/blob/master/proposals/0045-scan-takewhile-dropwhile.md>
>>>    - SE-0068 - Expanding Swift Self to class members and value types
>>>    <https://github.com/apple/swift-evolution/blob/master/proposals/0068-universal-self.md>
>>>    - SE-0075 - Adding a Build Configuration Import Test
>>>    <https://github.com/apple/swift-evolution/blob/master/proposals/0075-import-test.md>
>>>    - SE-0077 - Improved operator declarations
>>>    <https://github.com/apple/swift-evolution/blob/master/proposals/0077-operator-precedence.md>
>>>    - SE-0080 - Failable Numeric Conversion Initializers
>>>    <https://github.com/apple/swift-evolution/blob/master/proposals/0080-failable-numeric-initializers.md>
>>>    - SE-0081 - Move where clause to end of declaration
>>>    <https://github.com/apple/swift-evolution/blob/master/proposals/0081-move-where-expression.md>
>>>    - SE-0082 - Package Manager Editable Packages
>>>    <https://github.com/apple/swift-evolution/blob/master/proposals/0082-swiftpm-package-edit.md>
>>>    - SE-0088 - Modernize libdispatch for Swift 3 naming conventions
>>>    <https://github.com/apple/swift-evolution/blob/master/proposals/0088-libdispatch-for-swift3.md>
>>>    - SE-0089 - Renaming String.init<T>(_: T)
>>>    <https://github.com/apple/swift-evolution/blob/master/proposals/0089-rename-string-reflection-init.md>
>>>    - SE-0092 - Typealiases in protocols and protocol extensions
>>>    <https://github.com/apple/swift-evolution/blob/master/proposals/0092-typealiases-in-protocols.md>
>>>    - SE-0096 - Converting dynamicType from a property to an operator
>>>    <https://github.com/apple/swift-evolution/blob/master/proposals/0096-dynamictype.md>
>>>    - SE-0099 - Restructuring Condition Clauses
>>>    <https://github.com/apple/swift-evolution/blob/master/proposals/0099-conditionclauses.md>
>>>    - SE-0101 - Reconfiguring sizeof and related functions into a
>>>    unified MemoryLayout struct
>>>    <https://github.com/apple/swift-evolution/blob/master/proposals/0101-standardizing-sizeof-naming.md>
>>>    - SE-0102 - Remove @noreturn attribute and introduce an empty Never
>>>     type
>>>    <https://github.com/apple/swift-evolution/blob/master/proposals/0102-noreturn-bottom-type.md>
>>>    - SE-0103 - Make non-escaping closures the default
>>>    <https://github.com/apple/swift-evolution/blob/master/proposals/0103-make-noescape-default.md>
>>>    - SE-0104 - Protocol-oriented integers
>>>    <https://github.com/apple/swift-evolution/blob/master/proposals/0104-improved-integers.md>
>>>    - SE-0107 - UnsafeRawPointer API
>>>    <https://github.com/apple/swift-evolution/blob/master/proposals/0107-unsaferawpointer.md>
>>>    - SE-0110 - Distinguish between single-tuple and multiple-argument
>>>    function types
>>>    <https://github.com/apple/swift-evolution/blob/master/proposals/0110-distingish-single-tuple-arg.md>
>>>    - SE-0111 - Remove type system significance of function argument
>>>    labels
>>>    <https://github.com/apple/swift-evolution/blob/master/proposals/0111-remove-arg-label-type-significance.md>
>>>    - SE-0120 - Revise partition Method Signature
>>>    <https://github.com/apple/swift-evolution/blob/master/proposals/0120-revise-partition-method.md>
>>>    - SE-0127 - Cleaning up stdlib Pointer and Buffer Routines
>>>    <https://github.com/apple/swift-evolution/blob/master/proposals/0127-cleaning-up-stdlib-ptr-buffer.md>
>>> These are all changes the community has approved for Swift but did not
>>> make today's cutoff. Some of these proposals have implementations actively
>>> underway. For those proposals already in active development — *and near
>>> completion* — I am okay with extending the deadline for those changes
>>> to *Friday, July 29*. Such changes need to be approved by the release
>>> manager (myself) and should be merged into master via a pull request.
>>> When creating the pull request, please assign it to me (tkremenek), and
>>> mention the pull request on the swift-dev mailing list as well with the
>>> SE number in the email title.
>>> The rest of the unimplemented proposals do not make Swift 3. This leaves
>>> us with the question of what to do with them. These proposals represent the
>>> known and reviewed changes we want to make to Swift, but inevitably there
>>> will *also* be changes that we don't even know about today that we will
>>> want to take into Swift that can impact core source stability. That said,
>>> we also have a very strong desire to maintain source compatibility with
>>> Swift 3 and Swift 4 as much as possible to provide some stability for which
>>> Swift users to build upon. The challenge of course is reconciling these
>>> diametrically opposing goals: maintaining source stability while having the
>>> ability to incorporate more core (and important) language changes that are
>>> possibly source-breaking.
>>> The Swift team at Apple has reflected on this and decided what it
>>> "means" for Swift 3 to be source compatible with Swift 4 and later releases
>>> going forward. Our goal is to allow app developers to combine a mix of
>>> Swift modules (e.g., SwiftPM packages), where each module is known to
>>> compile with a specific version of the language (module A works with Swift
>>> 3, module B works with Swift 3.1, etc.), then combine those modules into a
>>> single binary. The key feature is that a module can be migrated from Swift
>>> 3 to 3.1 to 4 (and beyond) independently of its dependencies.
>>> While the exact details of how we will accomplish this feat are still
>>> being discussed, here is a sketch of how this will likely work in the Swift
>>> 4 timeframe. The key enabler is a new compiler flag that indicates the
>>> language version to compile for (e.g., similar to the clang -std=c99 flag).
>>> The compiler flag will be provided by the build system you are using (e.g.,
>>> Xcode, SwiftPM, etc.) on a per-module basis:
>>>    -
>>>    For language syntax/semantics, the compiler can use the language
>>>    mode to properly implement the language version being used by a module.
>>>    -
>>>    For the Standard Library, additive and subtractive changes are
>>>    easily handled (the former by just adding them, the later by using
>>>    deprecation techniques). For semantics changes, things are much more
>>>    complicated, and will need further study.
>>> The great thing about this approach is that a single Swift 4 compiler is
>>> building all of the sources in an application. This allows us to roll out
>>> this approach before achieving full ABI stability — something that will be
>>> a goal for Swift 4, but is impractical to achieve for a Swift 3.x release.
>>> It also provides us a general framework in the future for handling source
>>> compatibility as Swift evolves.
>>> To make this more concrete, suppose an application is written to use
>>> Swift 4, but uses packages via SwiftPM that are written using Swift 3. A
>>> single compiler would build both the app and the packages — thus ensuring
>>> that all the compiled sources are binary compatible. It would not be the
>>> case that a framework built with the Swift 3 compiler could be used by an
>>> app built using the Swift 4 compiler. That kind of library binary stability
>>> (ABI) will be a key goal of the Swift 4 release.
>>> These constraints mentioned above will serve as scaffolding for Swift 4
>>> development. Discussion about Swift 4 commences on Monday. Ahead of that,
>>> Chris Lattner plans to send out thoughts from the Core team on some of the
>>> known key goals (and non-goals) for the release. In the meantime, the focus
>>> over the next couple days should be taking stock of what has landed for
>>> Swift 3 and to see if any of the proposals mentioned above are close to
>>> being completed or are truly out of scope.
>>> Thank you again to everyone for making Swift 3 such as fantastic release!
>>> Ted
>>> _______________________________________________
>>> swift-evolution mailing list
>>> swift-evolution at swift.org
>>> https://lists.swift.org/mailman/listinfo/swift-evolution
>> _______________________________________________
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>> https://lists.swift.org/mailman/listinfo/swift-evolution
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