[swift-dev] Implementing New Syntax in Swift

Seth Friedman sethfri at gmail.com
Mon Jan 18 11:10:55 CST 2016

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.

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*
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