+1 - this is a useful feature in C-like languages. I'd prefer adding #error as
well - you can have a file that depends on the OS features and may want to have
a branch of the #if statements ending in
#if os(OSX)
/// ...
#if os(Linux)
/// ...
#else
#error("This OS isn't supported yet.").
#endif
> On May 29, 2016, at 6:36 AM, Robert Widmann via swift-evolution
> <swift-evolution@swift.org> wrote:
>
> #warning isn't exclusively used for FIXMEs. Languages that include these
> kinds of features do things like flag old modules or unsupported OSes and
> older Swift versions by combining it with #if - a feature Swift implements
> far richer conditionals for than other languages I might add. The kinds of
> developers that are reaching for these features, in addition to TODOs, are
> the ones that aren't letting their own warnings sit and get stale.
>
> ~Robert Widmann
>
> 2016/05/28 20:26、Jon Shier via swift-evolution <swift-evolution@swift.org
> <mailto:swift-evolution@swift.org>> のメッセージ:
>
>> I appreciate the sentiment, but I think we should reserve warnings for
>> actual compiler diagnostics. If you wish to add another, user definable
>> diagnostic type, like official compiler support for a #todo or #fixme flag,
>> then go ahead. But adding #warning because the IDE (read Xcode) doesn’t
>> automatically pick up FIXMEs or TODOs isn’t a compelling enough reason. In
>> addition, enabling developers to add their own warnings which can then just
>> be ignored just encourages the very bad habit of ignoring warnings in
>> general. Perhaps this could be something for libIDE, rather than the core
>> language?
>>
>>
>>
>> Jon Shier
>>
>>> On May 28, 2016, at 7:58 PM, Harlan Haskins via swift-evolution
>>> <swift-evolution@swift.org <mailto:swift-evolution@swift.org>> wrote:
>>>
>>> Hey everyone,
>>>
>>> I’m working on a draft for #warning in Swift. I’ve implemented the draft as
>>> it stands, and it’s pretty nice to work with.
>>>
>>> I’ve pasted it below, and I’d love some feedback! Thanks!
>>>
>>> — Harlan Haskins
>>>
>>>
>>>
>>> #warning
>>>
>>> Proposal: SE-NNNN
>>> <https://github.com/apple/swift-evolution/blob/master/proposals/NNNN-name.md>
>>> Author: Harlan Haskins <https://github.com/harlanhaskins>
>>> Status: Awaiting review
>>> <https://gist.github.com/harlanhaskins/bfe2d56d7655c5bfdb1855eaf00addb4#rationale>
>>> Review manager: TBD
>>>
>>> <https://gist.github.com/harlanhaskins/bfe2d56d7655c5bfdb1855eaf00addb4#introduction>Introduction
>>>
>>> It's really common for developers to add TODO/FIXME comments in their
>>> source code, but there currently isn't a supported facility to make these
>>> visible. People have implemented special workarounds
>>> <https://bendodson.com/weblog/2014/10/02/showing-todo-as-warning-in-swift-xcode-project/>
>>> to coax Xcode into emitting TODOs and FIXMEs as warnings, but there isn't
>>> an accessible way to provide arbitrary warnings, and does not work in a
>>> non-Xcode environment.
>>>
>>>
>>> <https://gist.github.com/harlanhaskins/bfe2d56d7655c5bfdb1855eaf00addb4#motivation>Motivation
>>>
>>> A #warning is for something you intend to fix before submitting your code
>>> or for writing future tasks that you or your teammates intend to complete
>>> later. Because this is such a common programming pattern, Swift should have
>>> a similar facility.
>>>
>>>
>>> <https://gist.github.com/harlanhaskins/bfe2d56d7655c5bfdb1855eaf00addb4#proposed-solution>Proposed
>>> solution
>>>
>>> Add #warning(_:) as a new compiler directive that emits a warning
>>> diagnostic with the contents, pointing to the start of the message.
>>>
>>> func configPath() -> String {
>>> #warning("TODO: load this more safely") // expected-warning {{TODO: load
>>> this more safely}}
>>> return Bundle.main().path(forResource: "Config", ofType: "plist")!
>>> }
>>>
>>> <https://gist.github.com/harlanhaskins/bfe2d56d7655c5bfdb1855eaf00addb4#detailed-design>Detailed
>>> design
>>>
>>> This will add two new productions to the Swift grammar:
>>>
>>> compiler-control-statement → warning-directive
>>> warning-directive → #warning( static-string-literal )
>>> Upon parsing this statement, the Swift compiler will immediately emit a
>>> warning and discard the statement.
>>>
>>> If a #warning exists inside a branch of a #if statement that is not taken,
>>> then no warning is emitted.
>>>
>>> #if false
>>> #warning(“This won’t exist”)
>>> #endif
>>>
>>> <https://gist.github.com/harlanhaskins/bfe2d56d7655c5bfdb1855eaf00addb4#impact-on-existing-code>Impact
>>> on existing code
>>>
>>> This change is purely additive; no migration will be required.
>>>
>>>
>>> <https://gist.github.com/harlanhaskins/bfe2d56d7655c5bfdb1855eaf00addb4#alternatives-considered>Alternatives
>>> considered
>>>
>>> We could do some kind of comment-parsing based approach to surface TODOs
>>> and FIXMEs, but #warning serves as a general-purpose facility for reporting
>>> at compile time. Plus, not all TODO or FIXME comments should surface as
>>> warnings in the source.
>>>
>>> _______________________________________________
>>> swift-evolution mailing list
>>> swift-evolution@swift.org <mailto:swift-evolution@swift.org>
>>> https://lists.swift.org/mailman/listinfo/swift-evolution
>>> <https://lists.swift.org/mailman/listinfo/swift-evolution>
>>
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