Rename UnevaluatedConst to AliasConst by Shourya742 · Pull Request #158115 · rust-lang/rust

Shourya742 · 2026-06-19T03:46:24Z

refer: rust-lang/project-const-generics#115

I only renamed the type system version to AliasConst/AliasConstKind. I did not rename MIR’s UnevaluatedConst, it currently holds direct def_id instead of kind variant we have in type-system. I also left rustc_public’s UnevaluatedConst unchanged.

rustbot · 2026-06-19T03:46:27Z

This PR changes rustc_public

cc @oli-obk, @celinval, @ouz-a, @makai410

changes to the core type system

cc @lcnr

Some changes occurred in const_evaluatable.rs

cc @BoxyUwU

Some changes occurred to the core trait solver

cc @rust-lang/initiative-trait-system-refactor

Some changes occurred in match checking

cc @Nadrieril

Some changes occurred to the CTFE / Miri interpreter

cc @rust-lang/miri, @RalfJung, @oli-obk, @lcnr

Some changes occurred in rustc_ty_utils::consts.rs

cc @BoxyUwU

HIR ty lowering was modified

cc @fmease

changes to the core type system

cc @lcnr

rustbot · 2026-06-19T03:46:28Z

Failed to set assignee to khyperia: invalid assignee

Note: Only org members with at least the repository "read" role, users with write permissions, or people who have commented on the PR may be assigned.

khyperia · 2026-06-19T06:03:21Z

thanks so much for working on this! ❤️

there's some more stuff that we want to rename related to this change (sorry for not being more clear in the issue description!):

ConstKind::Unevaluated (variant that just holds a UnevaluatedConst, its name should reflect what it contains)
Const::new_unevaluated (constructor for the previous variant)
- (and the Interner trait for new_unevaluated)
Interner::UnevaluatedConstId (this one is a bit sketch, I believe it's actually only used for anon consts, not all AliasConsts, so it should possibly be renamed to AnonConstId instead of AliasConstId. Please double check for me though and make a judgement call!)
perhaps little things like AliasTerm::to_term has a local named unevaluated_const, some other places also call local variables unevaluated. This is less important though, IMO!
- same thing that we have a relatively consistent naming that variables of type UnevaluatedConst are called uv, could possibly rename those as uv no longer makes sense. But, it's not as important, we can also clean this up over time, IMO.
lots of comments referring to Unevaluated that could be rephrased if you'd like (it'd be nice to not have to know the legacy information that these things used to be called unevaluated consts while reading comments, but not strictly necessary to update I suppose)
I need to remember to update the rustc dev guide (but honestly that's on me, that page is pretty out of date after my recent refactorings, I've been forgetting to update it)

I discovered the above list by running rg -i unevaluated in compiler/, and being like, "hmm, does this mention of the word 'unevaluated' have to do with the concept of UnevaluatedConst, or is it just talking about something in general being unevaluated? (and ignoring mir and rustc_public's UnevaluatedConst)". (Just letting you know so you can do the same kind of thing if you'd like! I might have missed some stuff)

Would you like to work on all this other stuff in phases, or would you rather do everything in one big PR? Up to you I think!

Shourya742 · 2026-06-19T11:12:50Z

Would you like to work on all this other stuff in phases, or would you rather do everything in one big PR? Up to you I think!

Thanks for thorough review and suggestions. I would like to get them in, in this PR itself (would be scary to ping these many people again). I will make sure to add commits for each update for easier review. I will reach out, if I have some doubts. Thanks.

Shourya742 · 2026-06-21T05:03:32Z

thanks so much for working on this! ❤️

there's some more stuff that we want to rename related to this change (sorry for not being more clear in the issue description!):

ConstKind::Unevaluated (variant that just holds a UnevaluatedConst, its name should reflect what it contains)

Const::new_unevaluated (constructor for the previous variant)

(and the Interner trait for new_unevaluated)

Interner::UnevaluatedConstId (this one is a bit sketch, I believe it's actually only used for anon consts, not all AliasConsts, so it should possibly be renamed to AnonConstId instead of AliasConstId. Please double check for me though and make a judgement call!)

perhaps little things like AliasTerm::to_term has a local named unevaluated_const, some other places also call local variables unevaluated. This is less important though, IMO!

same thing that we have a relatively consistent naming that variables of type UnevaluatedConst are called uv, could possibly rename those as uv no longer makes sense. But, it's not as important, we can also clean this up over time, IMO.

lots of comments referring to Unevaluated that could be rephrased if you'd like (it'd be nice to not have to know the legacy information that these things used to be called unevaluated consts while reading comments, but not strictly necessary to update I suppose)

I need to remember to update the rustc dev guide (but honestly that's on me, that page is pretty out of date after my recent refactorings, I've been forgetting to update it)

I think I have addressed most of these, I have few questions which I posted side by side to the code change. Super thanks for the review.

@khyperia (for some reason bors acting weird with assignments.)

khyperia · 2026-06-21T05:24:00Z

@khyperia (for some reason bors acting weird with assignments.)

I'm not actually part of the project 😅 (yet...), so I don't have r+ privs or stuff like that. But, I double checked with @BoxyUwU before making the issue for this change, and she (and a few other folks) are super on board with the change! (This change has been a long time coming I feel like)

Shourya742 · 2026-06-21T05:38:20Z

Ah!! let me try again, considering bors should do assignment based on comments.

r? @khyperia

yay!!! it did!

khyperia · 2026-06-21T05:38:51Z

        const HAS_TY_INHERENT             = 1 << 13;
-        /// Does this have `ConstKind::Unevaluated`?
+        /// Does this have `ConstKind::Alias`?
        const HAS_CT_PROJECTION           = 1 << 14;


This is totally unrelated to your PR, but I dislike the name of this bitflag. To me, HAS_CT_PROJECTION corresponds to having a AliasConstKind::Projection, just like HAS_TY_PROJECTION does, but no, the comment is correct, HAS_CT_PROJECTION corresponds to having any ConstKind::Alias. (Pointing this out in case any other reviewer sees this and has the same "???" as me)

View changes since the review

Yeah this is weird :3 follow up item to change this I think, probably at minimum we should rename this to HAS_CONST_ALIASES

rustbot · 2026-06-21T05:39:11Z

Some changes occurred to MIR optimizations

cc @rust-lang/wg-mir-opt

Some changes occurred to the CTFE machinery

cc @RalfJung, @oli-obk, @lcnr

Some changes occurred in abstract_const.rs

cc @BoxyUwU

Some changes occurred to constck

cc @fee1-dead

Some changes occurred in need_type_info.rs

cc @lcnr

khyperia

Looks great to me! Feel free to fix up the little nits/questions you had, but as they're not directly relevant to the core of the change, I'm also happy as-is. Thank you so much for working on this, it's gonna make it sooo much nicer to talk about these things, and help the readability of the compiler so much.

As for someone who can actually r+, I'm guessing anyone in the Const Generics Project Group (I'm guessing Boxy probably knows what's up here the best, but she's also very swamped with reviews, so idk)

View changes since this review

RalfJung · 2026-06-21T14:47:17Z

I did not rename MIR’s UnevaluatedConst,

I still like the "unevalutaed" name and don't understand how this is an "alias" (a const item is not an alias for anything?), so please discuss this with wg-const-eval and explain the issues with the current names before renaming anything on the MIR side. t-types is not the only group interacting with MIR constants, and to a non-types-person, this "alias" terminology is more confusing than helpful IMO.

(For type constants I have no objections to t-types picking whatever name you find most helpful, but when writing docs, please keep in mind that whatever analogy you see between type aliases and consts is unlikely to be obvious to others.)

BoxyUwU · 2026-06-23T08:37:19Z

        const HAS_TY_INHERENT             = 1 << 13;
-        /// Does this have `ConstKind::Unevaluated`?
+        /// Does this have `ConstKind::Alias`?
        const HAS_CT_PROJECTION           = 1 << 14;


Yeah this is weird :3 follow up item to change this I think, probably at minimum we should rename this to HAS_CONST_ALIASES

BoxyUwU · 2026-06-23T08:49:24Z

thx yeah this looks good to me, one nit & needs rebasing then can be merged. i agree with ralf that we shouldn't change the MIR constant stuff, that stuff will remain just being unevaluated consts rather than being type system consts.

thanks @khyperia for reviews and @Shourya742 for working on this 💚 im really happy to see this finally happen after years of having this awkward inconsistency 😅

BoxyUwU · 2026-06-23T08:52:44Z

@rustbot author

Shourya742 · 2026-06-23T13:50:26Z

Super Thanks @khyperia and @BoxyUwU for the reviews!!! :) Addressed the nits.

BoxyUwU · 2026-06-23T15:47:22Z

idk if this will conflict with #158013 or not :3

@bors r+ rollup=never p=1

rust-bors · 2026-06-23T15:47:25Z

📌 Commit 8f9b763 has been approved by BoxyUwU

It is now in the queue for this repository.

BoxyUwU · 2026-06-24T04:19:58Z

the answer was yes it will 😆

…asConstKind

* Const::new_unevaluated / interner method -> new_alias * Interner::UnevaluatedConstId -> AnonConstId, since assoc type is only used for anonnymous consts

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. WG-trait-system-refactor The Rustc Trait System Refactor Initiative (-Znext-solver) labels Jun 19, 2026

Shourya742 marked this pull request as draft June 19, 2026 03:48

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rust-cloud-vms Bot force-pushed the 2026-06-19-rename-unevaluatedConst-to-aliasconst branch from 73249cb to bea205a Compare June 19, 2026 04:38

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Shourya742 commented Jun 21, 2026

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Comment thread compiler/rustc_type_ir/src/predicate.rs Outdated

Comment thread compiler/rustc_type_ir/src/interner.rs Outdated

Comment thread compiler/rustc_hir_analysis/src/check/check.rs Outdated

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rust-cloud-vms Bot force-pushed the 2026-06-19-rename-unevaluatedConst-to-aliasconst branch from 9f77834 to 1309d08 Compare June 21, 2026 05:29

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Shourya742 marked this pull request as ready for review June 21, 2026 05:39

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rust-cloud-vms Bot force-pushed the 2026-06-19-rename-unevaluatedConst-to-aliasconst branch from f0c6dcd to 8f9b763 Compare June 23, 2026 12:15

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Shourya742 added 6 commits June 24, 2026 11:45

Rename unevaluatedConst to AliasConst and UnevaluatedConstKind to Ali…

80748e0

…asConstKind

* ConstKind::Unevaluated -> ConstKind::Alias

50b4bda

* Const::new_unevaluated / interner method -> new_alias * Interner::UnevaluatedConstId -> AnonConstId, since assoc type is only used for anonnymous consts

Correct the type_const_recursive error message to be not vague

91c3679

Remove unused bounds in interners

7ab309c

Rename uv to alias_const

316eda2

Rename from alias const to const alias and bless test

a8344e4

rust-cloud-vms Bot force-pushed the 2026-06-19-rename-unevaluatedConst-to-aliasconst branch from 8f9b763 to a8344e4 Compare June 24, 2026 11:52

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