Types are values of type `type` #2360

zygoloid · 2022-10-28T23:25:29Z

Define a "type" to be a value of type type. Contexts expecting a type perform an implicit conversion to type. Values like () and (i32, i32) and {} are no longer types, but instead implicitly convert to type. Values of interface or constraint type (now called "facets") are similarly not formally types but implicitly convert to type.

chandlerc

I did a quick review while its still fresh in my mind, and this largely matches my understanding of our discussions!

I'm pretty happy w/ the improved story across the board here. A somewhat minor added bit of prose suggested inline.

proposals/p2360.md

Co-authored-by: Chandler Carruth <chandlerc@gmail.com>

Co-authored-by: josh11b <josh11b@users.noreply.github.com>

Co-authored-by: Jon Ross-Perkins <jperkins@google.com>

proposals/p2360.md

Add a bunch of examples.

chandlerc

Approving for leads, this seems ready to land.

FWIW, I do think there are two things to keep our eyes on:

As mentioned in the proposal, we may need to revisit the whole tuple situation if this approach proves too confusing. But I think that's a fine fix-forward to keep open.
We may want to revisit or tweak the precise terminology. I even have some ideas of what might be an improvement here, but they seem better considered as incremental changes in the future rather than trying to keep iterating here.

If Josh is happy merging my typo fix, one of us can likely merge the whole PR afterward.

proposals/p2360.md

Co-authored-by: Chandler Carruth <chandlerc@gmail.com>

…or review comments.

Also make minor updates to the skeletal design in docs/design/name_lookup.md following carbon-language#2113, as there are no longer any prelude names that are made available to unqualified name lookup by default. Add `type` to the keyword list in docs/design/lexical_conventions/words.md, following carbon-language#2360.

Also make minor updates to the skeletal design in docs/design/name_lookup.md following #2113, as there are no longer any prelude names that are made available to unqualified name lookup by default. Add `type` to the keyword list in docs/design/lexical_conventions/words.md, following #2360.

This reflects changes from a number of approved proposals: - #920 : concrete statements about orphan and overlap in Carbon - #2138 : "generic" -> "checked generic", "template" -> "template generic" - #2188 : binding patterns are forbidden in type position - #2360 : "type", "facet type", "facet". Note: I am not using the term "generic type" from #2360 since that meaning conflicts with the generally accepted meaning of "generic type" of a type with a compile-time parameter. - #2760 / #2770 : internal/external impl -> extending impl - #2964 : "symbolic constant" and "template constant" --------- Co-authored-by: Geoff Romer <gromer@google.com> Co-authored-by: Richard Smith <richard@metafoo.co.uk>

This reflects changes from a number of approved proposals: - #2138 : "generic" -> "checked generic", "template" -> "template generic" - #2360 : "type", "facet type", "facet". Note: I am not using the term "generic type" from #2360 since that meaning conflicts with the generally accepted meaning of "generic type" of a type with a compile-time parameter. - #2760 / #2770 : internal/external impl -> extending impl - #2964 : "symbolic constant" and "template constant" --------- Co-authored-by: Richard Smith <richard@metafoo.co.uk>

Change terminology away from terms that are ambiguous: - Reserve "generic type" for types with (compile-time) parameters, like `Vector` in `Vector(T:! type)`. Don't use that term to refer to `T`, as it would with [#2360](https://github.com/carbon-language/carbon-lang/blob/trunk/proposals/p2360.md#terminology). - Use the term "compile-time" instead of "constant" to mean "template or symbolic." Expand the term "constant" to include values, such as from `let` bindings.

Most changes are due to proposal #2360, but this also includes changes to reflect: #1136, #2138, #2006, #2550, and #2964. --------- Co-authored-by: Richard Smith <richard@metafoo.co.uk>

Incorporates proposals: #1885, #2138, #2188, #2200, #2360, #2760, #2964, and #3162. --------- Co-authored-by: Richard Smith <richard@metafoo.co.uk>

First step in updating `docs/design/generics/details.md`. It incorporates changes from proposals: #989 #2138 #2173 #2200 #2360 #2964 #3162 , but there are still more changes from those proposals to be made. It also switches away from suggesting static-dispatch witness tables, and creates an appendix to describe that decision. --------- Co-authored-by: Richard Smith <richard@metafoo.co.uk>

Includes proposals: - #990 - #2188 - #2138 - #2200 - #2360 - #2760 - #2964 - #3162 Also tries to use more precise language when talking about: - implementations, to avoid confusing `impl` declaration and definitions with the `impls` operator used in `where` clauses, an issue brought up in #2495 and #2483; - "binding patterns", like `x: i32`, and "bindings" like `x`. --------- Co-authored-by: Chandler Carruth <chandlerc@gmail.com>

Continued from part 1: #3231. Second step updating `docs/design/generics/details.md`. There remains some work to incorporate proposal #2200. - The biggest changes are incorporating much of the text of proposals: - #2173 - #2687 - It incorporates changes from proposals: - #989 - #1178 - #2138 - #2200 - #2360 - #2964 - #3162 - It also updates the text to reflect the latest thinking from leads issues: - #996 - #2153 -- most notably deleting the section on `TypeId`. - Update to rule for prioritization blocks with mixed type structures from [discussion on 2023-07-18](https://docs.google.com/document/d/1gnJBTfY81fZYvI_QXjwKk1uQHYBNHGqRLI2BS_cYYNQ/edit?resourcekey=0-ql1Q1WvTcDvhycf8LbA9DQ#heading=h.7jxges9ojgy3) - Adds reference links to proposals, issues, and discussions relevant to the text. - Also tries to use more precise language when talking about implementations, to avoid confusing `impl` declaration and definitions with the `impls` operator used in `where` clauses, an issue brought up in - #2495 - #2483 --------- Co-authored-by: Richard Smith <richard@metafoo.co.uk>

zygoloid added proposal A proposal proposal draft Proposal in draft, not ready for review labels Oct 28, 2022

Filling out template with PR 2360

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zygoloid force-pushed the proposal-types-are-values-of- branch from b0f0ff6 to 7cf53a2 Compare October 28, 2022 23:25

zygoloid mentioned this pull request Oct 29, 2022

Replace some (all?) type equality with subtyping #495

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Initial proposal draft.

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Link to carbon-language#2360

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zygoloid and others added 6 commits October 31, 2022 14:04

Update proposals/p2360.md

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Co-authored-by: Chandler Carruth <chandlerc@gmail.com>

Update proposals/p2360.md

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Co-authored-by: josh11b <josh11b@users.noreply.github.com>

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Co-authored-by: Jon Ross-Perkins <jperkins@google.com>

Responses to review comments.

0f73ca8

Rephrase a little more.

fa70880

Improve terminology.

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jonmeow mentioned this pull request Oct 31, 2022

Structure, scope, and naming of the prelude and syntax aliases #2113

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zygoloid mentioned this pull request Oct 31, 2022

Template generics #2200

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Updates based on design discussion and feedback.

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josh11b mentioned this pull request Nov 10, 2022

Should some values be self-typed? If so, which ones? #508

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zygoloid changed the title ~~Types are values of type Type~~ Types are values of type type Nov 10, 2022

More updates based on feedback.

525a0ee

Add a bunch of examples.

chandlerc self-requested a review December 22, 2022 04:53

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Co-authored-by: Chandler Carruth <chandlerc@gmail.com>

chandlerc merged commit 16dcdc2 into carbon-language:trunk Dec 22, 2022

zygoloid added a commit to zygoloid/carbon-lang that referenced this pull request Jan 3, 2023

Update terminology to match carbon-language#2360 and address some min…

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zygoloid mentioned this pull request Jan 4, 2023

Rename Type -> type, per #2360. #2507

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chandlerc mentioned this pull request Feb 5, 2023

Generics external impl versus extends #995

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jonmeow mentioned this pull request Feb 10, 2023

Polish out support for reals and strings. #2593

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josh11b mentioned this pull request Feb 23, 2023

when are facet types equal? #2409

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josh11b mentioned this pull request Apr 11, 2023

Proposal: Variadics #2240

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Update Generics terminology document #3048

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Update generics overview #3061

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Update member_access.md to reflect accepted proposals #3160

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Update design overview to reflect submitted proposals #3180

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This was referenced Sep 14, 2023

Updates to generics design details, part 1 #3231

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Generic let with auto? #996

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This was referenced Sep 19, 2023

Is let referentially transparent? #1371

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Updates to generics design details, part 2 #3253

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Updates to design docs to reflect accepted proposals #3254

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zygoloid deleted the proposal-types-are-values-of- branch October 4, 2023 23:27

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Types are values of type `type` #2360

Types are values of type `type` #2360

zygoloid commented Oct 28, 2022 •

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Types are values of type type #2360

Types are values of type type #2360

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Types are values of type `type` #2360

Types are values of type `type` #2360

zygoloid commented Oct 28, 2022 •

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