[swift-dev] Implementing New Syntax in Swift

Svein Halvor Halvorsen svein.h at lvor.halvorsen.cc
Mon Jan 18 11:13:40 CST 2016

So you want a completely new kind of literal, that is neither a string,
integer, float, etc.
Kinda like the special array and dictionary literals?

2016-01-18 18:10 GMT+01:00 Seth Friedman <sethfri at gmail.com>:

> Sure, but this is a completely arbitrary, simple example designed to
> illustrate how to add new syntax to Swift. Conforming to
> IntegerLiteralConvertible would defeat the point of the exercise.
> Thanks,
> Seth
> On Mon, Jan 18, 2016 at 8:55 AM Svein Halvor Halvorsen <
> svein.h at lvor.halvorsen.cc> wrote:
>> Can't you just make your SuperInt conform to IntergerLiteralConvertible
>> and initialise it like so:
>> let superIntExample: SuperInt = 100
>> sv.
>> 2016-01-18 1:13 GMT+01:00 Seth Friedman via swift-dev <
>> swift-dev at swift.org>:
>>> Created SR-569 <https://bugs.swift.org/browse/SR-569> to track this
>>> Thanks!
>>> Seth
>>> On Sun, Jan 10, 2016 at 4:18 PM, Seth Friedman <sethfri at gmail.com>
>>> wrote:
>>>> Changing the subject of this thread since it's now an entirely
>>>> different question than what I originally asked. Hopefully this will result
>>>> in better visibility in getting an answer as well.
>>>> Thanks,
>>>> Seth
>>>> On Sun, Jan 10, 2016 at 4:16 PM Seth Friedman <sethfri at gmail.com>
>>>> wrote:
>>>>> Thanks Jordan!
>>>>> Here's a specific flow I'm interested in understanding. Note that this
>>>>> is just a wild example that would help me better understand parts of the
>>>>> compiler I'm interested in rather than any sort of proposal for the
>>>>> language.
>>>>> Let's say I have a type called SuperInt that has some cool integer
>>>>> operations that would be applicable and useful to everyone writing Swift.
>>>>> It's a given that this makes sense to be in the Swift language, and people
>>>>> are going to be using it so often that it makes sense to create a new
>>>>> literal syntax for this type. I'd like users to be able to instantiate a
>>>>> SuperInt with the following:
>>>>> let superIntExample = %^100^%
>>>>> Crazy syntax for a crazy example, but I wanted to make sure it's not
>>>>> something that's already in Swift. In this example, my SuperInt would be
>>>>> instantiated with a value of 100.
>>>>> I'd like to know the parts of the Swift compiler I would need to
>>>>> understand and change to implement this new type with its new syntax.
>>>>> I really this question requires a lengthy answer, but I think it would
>>>>> make a great start to a Swift internals manual (which I agree with you
>>>>> would be a fantastic idea).
>>>>> Anyone's help would be much appreciated!
>>>>> Thanks,
>>>>> Seth
>>>>> On Fri, Dec 18, 2015 at 5:25 PM Jordan Rose <jordan_rose at apple.com>
>>>>> wrote:
>>>>>> Hi, Seth. Sorry for not getting back to you sooner! I don't think we
>>>>>> have anything exactly like this, but there's *sort* of a sequence
>>>>>> diagram in Chris and Joe's talk at the LLVM conference, "Swift's
>>>>>> High-Level IR <https://youtu.be/Ntj8ab-5cvE>". I'd say it looks
>>>>>> something like this:
>>>>>> 1. Parsing
>>>>>> 2. Semantic analysis, including type-checking
>>>>>> 3. SIL generation
>>>>>> 4. Mandatory SIL passes
>>>>>> 5. SIL optimization
>>>>>> 6. LLVM IR generation
>>>>>> 7. LLVM optimization
>>>>>> 8. LLVM output (usually including machine code generation and writing
>>>>>> to a .o file)
>>>>>> …with the last two handled pretty much completely by LLVM
>>>>>> <http://llvm.org> itself, and not customized by Swift.
>>>>>> We probably ought to have something like Clang's "Internals
>>>>>> <http://clang.llvm.org/docs/InternalsManual.html>" manual (hopefully
>>>>>> better), which lays out the major concepts in each library. As it is we
>>>>>> have various concepts that are documented very well, either in docs/ or in
>>>>>> header comments, and others which are just arcane knowledge in the heads of
>>>>>> the implementers. This is not a good thing.
>>>>>> The "Contributing <https://swift.org/contributing/>" page on the
>>>>>> website lists a handful of ways to get involved; another one we're still
>>>>>> bringing up is issues with the "StarterBug" label in JIRA. These are
>>>>>> intended to be bugs that a newcomer could use as a goal-oriented way to
>>>>>> learn about one part of the project.
>>>>>> Of course, we're happy to answer any specific questions you might
>>>>>> have (and this list is probably the right place for them). It's the general
>>>>>> ones that are hard. :-)
>>>>>> Jordan
>>>>>> On Dec 16, 2015, at 2:36, Seth Friedman <sethfri at gmail.com> wrote:
>>>>>> Thanks Jordan!
>>>>>> Another question if anyone has some time: I'm really interested in
>>>>>> contributing to the project, but given that I don't have a ton of
>>>>>> experience with compilers, I'm having a really hard time following the flow
>>>>>> of the program. I understand that the high level flow is lexing, parsing,
>>>>>> sema, and building the AST. However, tracing through the actual functions
>>>>>> in the compiler prove much more difficult due to the amount of
>>>>>> indirection/metaprogramming.
>>>>>> Are there any sort of sequence diagrams that I haven't found yet? If
>>>>>> anyone could let me know of any good resources you know of, that would be
>>>>>> great. I'm sure this would also be of use to people in my boat that want to
>>>>>> help but don't know how to start.
>>>>>> Thanks,
>>>>>> Seth
>>>>>> On Tue, Dec 8, 2015 at 9:04 PM Jordan Rose <jordan_rose at apple.com>
>>>>>> wrote:
>>>>>>> Hi, Seth. I think you're getting Clang / swift-clang mixed up with
>>>>>>> swiftc / swift. Clang is not the Swift compiler; the Swift compiler lives
>>>>>>> in the "swift" repo. Swift depends on Clang for its interoperation with C
>>>>>>> and Objective-C.
>>>>>>> A *lot* of the compiler encodes information about Optional, but
>>>>>>> most of it stems from ASTContext.h and ASTContext.cpp, which has dedicated
>>>>>>> entrypoints for getting Optional, Optional.None, and Optional.Some.
>>>>>>> Hope this helps,
>>>>>>> Jordan
>>>>>>> On Dec 8, 2015, at 17:59 , Seth Friedman via swift-dev <
>>>>>>> swift-dev at swift.org> wrote:
>>>>>>> Hi all,
>>>>>>> In Optional.swift in the stdlib, there's a comment that says "The
>>>>>>> compiler has special knowledge of Optional<Wrapped>, including the fact
>>>>>>> that it is an enum with cases named 'None' and 'Some'."
>>>>>>> What I'm trying to understand is: If I wanted to implement the
>>>>>>> optional type from scratch, what would be the process I would go through?
>>>>>>> I've scoured the swift-clang project and can't seem to find any reference
>>>>>>> to optionals or even Swift explicitly. I discovered nullability attributes
>>>>>>> and am hypothesizing that an expression of something like "Type?" is
>>>>>>> somehow mapped to an attribute, but I'm really just stumbling around in the
>>>>>>> dark.
>>>>>>> In terms of what I've tried, I've gone through a lot of the source
>>>>>>> in the swift-clang lib/Basic and lib/AST directories, and I've read through
>>>>>>> the "Clang CFE Internals Manual" on the Clang website.
>>>>>>> Help is much appreciated!
>>>>>>> Thanks in advance,
>>>>>>> Seth
>>>>>>> _______________________________________________
>>>>>>> swift-dev mailing list
>>>>>>> swift-dev at swift.org
>>>>>>> https://lists.swift.org/mailman/listinfo/swift-dev
>>> --
>>> Seth Friedman
>>> *Software Development Engineer II*
>>> *Amazon.com*
>>> _______________________________________________
>>> swift-dev mailing list
>>> swift-dev at swift.org
>>> https://lists.swift.org/mailman/listinfo/swift-dev
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