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Generics: Set associated constants using where constraints #1013

Merged
merged 11 commits into from
Jan 27, 2022
Merged

Generics: Set associated constants using where constraints #1013

merged 11 commits into from
Jan 27, 2022

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josh11b
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@josh11b josh11b commented Jan 7, 2022

Change the syntax for setting the associated constants and types in an interface implementation for a type from using let declarations as in:

class Vector(T:! Type) {
  impl as Iterable {
    let ElementType:! Type = T;
    ...
  }
}

to using where clauses as in:

class Vector(T:! Type) {
  impl as Iterable where .ElementType = T {
    ...
  }
}

This is an attempt to simplify by removing redundancy, improve consistency by removing a use of let that was different than other examples, and better support forward declaration that a type implements an interface while retaining the information needed for type checking.

@josh11b josh11b added the proposal A proposal label Jan 7, 2022
@josh11b josh11b requested a review from a team January 7, 2022 23:32
@josh11b josh11b added this to Draft in Proposals via automation Jan 7, 2022
@josh11b josh11b marked this pull request as ready for review January 12, 2022 01:29
@josh11b josh11b requested a review from a team as a code owner January 12, 2022 01:29
@josh11b josh11b moved this from Draft to RFC in Proposals Jan 12, 2022
@josh11b josh11b requested a review from zygoloid January 12, 2022 01:29
@github-actions github-actions bot added the proposal rfc Proposal with request-for-comment sent out label Jan 12, 2022
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@zygoloid zygoloid left a comment

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Looks good to me; soliciting broader input before approval.

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Co-authored-by: Richard Smith <richard@metafoo.co.uk>
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@chandlerc chandlerc left a comment

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Some somewhat random thoughts here, but generally I really like this. I think its a great simplification & fix of a nagging issue. Super happy.

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LGTM, approving mostly on @zygoloid 's review, but I also am really happy here. =]

@josh11b josh11b merged commit b1b9d98 into carbon-language:trunk Jan 27, 2022
Proposals automation moved this from RFC to Accepted Jan 27, 2022
@josh11b josh11b deleted the set branch January 27, 2022 19:18
@github-actions github-actions bot added proposal accepted Decision made, proposal accepted and removed proposal rfc Proposal with request-for-comment sent out labels Jan 27, 2022
@zygoloid zygoloid mentioned this pull request Apr 15, 2022
chandlerc pushed a commit that referenced this pull request Jun 28, 2022
Change the syntax for setting the associated constants and types in an interface implementation for a type from using `let` declarations as in:
```
class Vector(T:! Type) {
  impl as Iterable {
    let ElementType:! Type = T;
    ...
  }
}
```
to using `where` clauses as in:
```
class Vector(T:! Type) {
  impl as Iterable where .ElementType = T {
    ...
  }
}
```

This is an attempt to simplify by removing redundancy, improve consistency by removing a use of `let` that was different than other examples, and better support forward declaration that a type implements an interface while retaining the information needed for type checking.

Co-authored-by: Richard Smith <richard@metafoo.co.uk>
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3 participants