Allow syntax extensions which modify and decorate #33738

dylanmckay · 2016-05-19T11:34:18Z

This adds a new SyntaxExtension type - Renovator.

A renovator is a syntax extension which can modify and decorate the items it is attached to - the union of MultiModifier and MultiDecorator.

This allows things such as syntax extensions which modify existing methods for types, and implement traits all in one.

This shouldn't break any existing code, and it only touches unstable compiler internals.

rust-highfive · 2016-05-19T11:34:31Z

r? @sfackler

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sfackler · 2016-05-19T16:18:06Z

This has been something I've been meaning to do for a while - I think the whole split into decorators and modifiers was a bad design decision on my part. To that end, I'd like to move towards removing the other variants and making this the only one.

cc @nrc

sfackler · 2016-05-19T16:19:01Z

src/libsyntax/ext/base.rs

+              meta_item: &ast::MetaItem,
+              item: Annotatable,
+              push: &mut FnMut(Annotatable))
+              -> Annotatable;


Seems like we can drop the return type and just have implementors push all of the things they're creating/preserving into push?

That is a good idea, I'm adding this in now.

bors · 2016-05-26T18:35:43Z

☔ The latest upstream changes (presumably #33766) made this pull request unmergeable. Please resolve the merge conflicts.

sfackler · 2016-05-26T18:38:53Z

Looks like travis is failing and it needs a rebase. Looks good to me otherwise though.

r? @nrc

nrc · 2016-05-27T00:58:33Z

cc @cswords
Looks fine to me too. Note that we are looking at revamping syntax extensions completely over the next few months, so this is all likely to disappear. However, it's probably worth landing this since new syntax extensions will be closer to these Renovators than to the existing flavours.

dylanmckay · 2016-05-27T09:47:27Z

Travis seems to be having unrelated issues. apt-get update is failing.

bors · 2016-05-28T03:53:54Z

☔ The latest upstream changes (presumably #33706) made this pull request unmergeable. Please resolve the merge conflicts.

dylanmckay · 2016-06-01T11:22:45Z

Am working on fixing this up.

dylanmckay · 2016-06-05T09:32:47Z

@nrc: Have rewritten the PR so that renovators must push all items which they want to preserve.

This is ready for review.

nrc · 2016-06-07T08:50:06Z

Why must users push the items themselves? That seems a bit counter-intuitive. At the least it needs to be documented somewhere.

Given that the renovator behaviour is a strict super-set of decorator and modifier, it would be cool to see their code refactored to just use the renovator code. Would that be possible?

dylanmckay · 2016-06-08T09:04:53Z

Why must users push the items themselves?

@nrc: @sfackler suggested this behaviour in this comment. I agree with it, and it gives the most flexibility to extensions.

Happy to document it more.

Given that the renovator behaviour is a strict super-set of decorator and modifier, it would be cool to see their code refactored to just use the renovator code. Would that be possible?

It's tricky to merge the three, as there is special handling for the new things that modifiers create. I can merge the Decorator and Renovator expansion code however.

This adds a new SyntaxExtension type - Renovator. A renovator is a syntax extension which can modify *and* decorate the items it is attached to - the union of `MultiModifier` and `MultiDecorator`. This allows things such as syntax extensions which modify existing methods for types, and implement traits all in one.

bors · 2016-06-08T12:02:00Z

☔ The latest upstream changes (presumably #34010) made this pull request unmergeable. Please resolve the merge conflicts.

nrc · 2016-06-08T12:50:33Z

@nrc: @sfackler suggested this behaviour in this comment. I agree with it, and it gives the most flexibility to extensions.

Happy to document it more.

Ok, that sounds good, more docs would be good though.

It's tricky to merge the three, as there is special handling for the new things that modifiers create. I can merge the Decorator and Renovator expansion code however.

What about the new things renovators create? Is this not the same handling?

dylanmckay · 2016-06-09T07:59:21Z

What about the new things renovators create? Is this not the same handling?

Modifiers have this special handling expand all the new stuff from the modifier. Decorators and renovators don't need it.

nrc · 2016-06-10T14:51:18Z

Why don't renovators need it, I'd have thought a renovator which doesn't create new items should behave exactly like a modifier?

dylanmckay · 2016-06-10T22:39:48Z

No idea, it's just what the current code does.

On Sat, Jun 11, 2016 at 2:51 AM, Nick Cameron [email protected]
wrote:

Why don't renovators need it, I'd have thought a renovator which doesn't
create new items should behave exactly like a modifier?

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nrc · 2016-06-23T04:12:56Z

This PR is superseded by #34253 which achieves a similar goal without adding a new class of macro. Sorry this PR didn't get to land and thanks for submitting it.

rust-highfive assigned sfackler May 19, 2016

dylanmckay force-pushed the more-flexible-syntax-extensions branch from afadda2 to 1eab42e Compare May 19, 2016 12:50

sfackler reviewed May 19, 2016
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dylanmckay mentioned this pull request May 23, 2016

More ergonomic class definition dylanmckay/rurust#1

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rust-highfive assigned nrc and unassigned sfackler May 26, 2016

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dylanmckay added 2 commits June 8, 2016 21:39

Make Renovators push all items they wish to preserve

dbd5017

dylanmckay force-pushed the more-flexible-syntax-extensions branch from 58d1ae6 to dbd5017 Compare June 8, 2016 09:40

nrc closed this Jun 23, 2016

dylanmckay deleted the more-flexible-syntax-extensions branch February 4, 2017 10:21

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Allow syntax extensions which modify and decorate #33738

Allow syntax extensions which modify and decorate #33738

dylanmckay commented May 19, 2016

rust-highfive commented May 19, 2016

sfackler commented May 19, 2016

sfackler May 19, 2016

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nrc commented Jun 23, 2016

Allow syntax extensions which modify and decorate #33738

Allow syntax extensions which modify and decorate #33738

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