.forbids pragma: defining forbidden tags #20050

Lancer11211 · 2022-07-17T12:39:29Z

Hi,
I've made this to handle my use case we've discussed under this forum post. My tests are located at tests/effects/teffects1(1-7).nim. Let me know if you're willing to accept this PR and if anything needs to be done before merging. Thank you!

Araq · 2022-07-17T13:01:49Z

Excellent work. But we need to bikeshed about the name. "notTags"? How about "prevents"? "avoids"? "forbids"?

Lancer11211 · 2022-07-17T13:06:42Z

Thank you! forbids sounds good to me. Let me know if it's final and I'll update the code.

Lancer11211 · 2022-07-17T13:18:17Z

Meanwhile, I've added another test: tests/effects/teffects12.nim - this is the one I mentioned in the forum post. It's a simple code which enables safe locking for a resource while disabling recurrent locks.

This patch intends to define the opposite of the .tags pragma: a way to define effects which are not allowed in a proc.

Lancer11211 · 2022-07-17T13:54:55Z

I've renamed the pragma to forbids and truncated the commits.

Araq · 2022-07-17T14:45:23Z

We also need a manual update, a changelog entry and an RFC. Maybe the RFC got already written though. And I don't say this to demotivate you, I'll help you push it through.

We need to focus especially on the subtyping relation between type T = proc () {.forbids: [E].} and type T = proc () < no forbids specified>.

Lancer11211 · 2022-07-17T15:01:22Z

Of course, I'll update the doc/manual.md and the changelog.md. I'll let you know when it's ready. I think this RFC is relevant: nim-lang/RFCs#302

the forbids pragma didn't handle simple restrictions properly and it also had issues with subtyping

Lancer11211 · 2022-07-17T16:22:26Z

While I was writing the documentation, I've found 2 bugs in the patch so I fixed them(and added 2 tests as coverage) before pushing this documentation/changelog update - let me know if you need anything added.

Araq · 2022-07-17T21:54:04Z

The type relation must be documented and justified.

Lancer11211 · 2022-07-17T22:30:01Z

Do you mean like this?

arnetheduck · 2022-07-18T06:23:54Z

Excellent work. But we need to bikeshed about the name. "notTags"? How about "prevents"? "avoids"? "forbids"?

At the core of this need for a new pragma lies a semantic difference: tags are additive while raises are not, ergo tags needs two pragmas - if we treat tags like exceptions (more or less), the alternative design here is that we have a pragma that works like raises which explicitly lists all tags that a function can propagate instead of "adding" and "forbidding".

wrong, per commend below

doc/manual.md

Araq · 2022-07-18T11:02:32Z

tags are additive while raises are not

I don't know why you keep phrasing it this way. Raises are additive too, except that try except can undo a raises effect. A general "undo tag" feature can be currently approximated via {.cast(tags: []).}. With the possible extension .cast(onlyAllows: [E])

arnetheduck · 2022-07-18T13:25:12Z

I don't know why you keep phrasing it this way.

my bad, got confused by some test code

Lancer11211 · 2022-07-18T14:32:25Z

I've corrected the patch to properly support proc type subtyping and I've updated the manual too.

Araq · 2022-07-18T19:20:32Z

doc/manual.md

+  caller2(toBeCalled2)
+
+`ProcType2` is a subtype of `ProcType1`. Unlike with tags, the parent context
+doesn't inherit the forbidden list of effects.


What does that mean "the parent context doesn't inherit"? What is the "parent context"?

Let's say function1 calls function2 - then function1 is the "parent context". I'm calling it a context because it's a context of effects in terms of the effect system. I can't really articulate it, but I wanted to refer to a hierarchy of function calls and statements.

I've added a little clarification to that line.

Araq · 2022-07-20T06:58:09Z

The CI is red because you need to update the docgen tests too.

Please run:

nim c -r -d:nimTestsNimdocFixup nimdoc/tester.nim

Lancer11211 · 2022-07-20T16:53:14Z

Thanks! I updated the docs and pull from devel.

Lancer11211 · 2022-07-20T23:35:08Z

It seems like I'm still missing something:

FAILURE: files differ: nimdoc/testproject/htmldocs/testproject.html
diff --git a/nimdoc/testproject/expected/testproject.html b/nimdoc/testproject/htmldocs/testproject.html

I tried nim c -r -d:nimTestsNimdocFixup nimdoc/testproject/testproject.nim but it didn't change anything.

Lancer11211 · 2022-07-22T21:36:03Z

Seems like the CI passed. Previously, I used nim c -r ... instead of ./bin/nim c -r ... which messed up the generated files.

Lancer11211 · 2022-07-25T12:07:14Z

Do we need anything else for the merge?

changelog.md

Co-authored-by: ringabout <[email protected]>

compiler/semcall.nim

github-actions · 2022-07-26T05:49:56Z

Thanks for your hard work on this PR!
The lines below are statistics of the Nim compiler built from efd5c57

Hint: mm: orc; threads: on; opt: speed; options: -d:release
163520 lines; 15.201s; 841.215MiB peakmem

Lancer11211 · 2022-07-26T06:34:06Z

Thanks for the review and the merge!

dom96 · 2022-07-26T14:16:34Z

This is beautiful, thank you for implementing it!

* .forbids pragma: defining illegal effects for proc types This patch intends to define the opposite of the .tags pragma: a way to define effects which are not allowed in a proc. * updated documentation and changelogs for the forbids pragma * renamed notTagEffects to forbiddenEffects * corrected issues of forbids pragma the forbids pragma didn't handle simple restrictions properly and it also had issues with subtyping * removed incorrect character from changelog * added test to cover the interaction of methods and the forbids pragma * covering the interaction of the tags and forbids pragmas * updated manual about the forbids pragma * removed useless statement * corrected the subtyping of proc types using the forbids pragma * updated manual for the forbids pragma * updated documentations for forbids pragma * updated nim docs * updated docs with rsttester.nim * regenerated documentation * updated rst docs * Update changelog.md Co-authored-by: ringabout <[email protected]> * updated changelog * corrected typo Co-authored-by: ringabout <[email protected]>

.forbids pragma: defining illegal effects for proc types

55f57cd

This patch intends to define the opposite of the .tags pragma: a way to define effects which are not allowed in a proc.

Lancer11211 changed the title ~~.notTags pragma: defining forbidden tags~~ .forbids pragma: defining forbidden tags Jul 17, 2022

Lancer added 3 commits July 17, 2022 17:24

updated documentation and changelogs for the forbids pragma

6961b55

renamed notTagEffects to forbiddenEffects

ee9cfae

corrected issues of forbids pragma

f89f019

the forbids pragma didn't handle simple restrictions properly and it also had issues with subtyping

Lancer added 3 commits July 17, 2022 18:26

removed incorrect character from changelog

1e9f08a

added test to cover the interaction of methods and the forbids pragma

4c321e1

covering the interaction of the tags and forbids pragmas

1f5f596

updated manual about the forbids pragma

139b4d7

Araq reviewed Jul 18, 2022

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Lancer added 3 commits July 18, 2022 16:21

removed useless statement

22d8df8

corrected the subtyping of proc types using the forbids pragma

5b5cfcf

updated manual for the forbids pragma

3fc7865

Araq reviewed Jul 18, 2022

View reviewed changes

updated documentations for forbids pragma

0fc3ccb

updated nim docs

288a208

Merge github.com:nim-lang/Nim into devel

9f21c8e

updated docs with rsttester.nim

0cba30e

Lancer added 2 commits July 22, 2022 17:42

regenerated documentation

c923af7

updated rst docs

4bbe4bd

Merge github.com:nim-lang/Nim into devel

db0b0a8

Lancer11211 mentioned this pull request Jul 25, 2022

Effect System: Tags that are disallowed by default, and blocking tag propagation nim-lang/RFCs#302

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ringabout reviewed Jul 25, 2022

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Lancer11211 and others added 2 commits July 25, 2022 14:55

Update changelog.md

49616c9

Co-authored-by: ringabout <[email protected]>

updated changelog

68c256e

linkmonitor reviewed Jul 25, 2022

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compiler/semcall.nim Outdated Show resolved Hide resolved

corrected typo

f9b8f4e

Araq merged commit efd5c57 into nim-lang:devel Jul 26, 2022

ringabout mentioned this pull request Oct 9, 2022

fixes #20524; add forbids pragmas to hideable lists #20525

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.forbids pragma: defining forbidden tags #20050

.forbids pragma: defining forbidden tags #20050

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.forbids pragma: defining forbidden tags #20050

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