Move Region from rustc_middle to rustc_type_ir by Jamesbarford · Pull Request #154989 · rust-lang/rust

Jamesbarford · 2026-04-08T14:47:55Z

General notes

Probably best reviewed commit by commit. I've tried where to make the changes as isolated as possible.

For the pub struct Region if we use Interned<...> in the definition then we'd need to add a lifetime to the Interner trait. As such I opted for a type InternedRegionKind which is Interned<'tcx, RegionKind<'tcx>> in the implementation. To allow calling the kind() method I implemented inherent::IntoKind for Interned<'tcx, T>.
All methods from the Region trait in inherent have been moved to compiler/rustc_type_ir/src/sty/mod.rs.
Had to implement Lift manually for Interned<RegionKind> (I::InternedRegionKind) which is a no-op.
I'm not sure the implementation of kind() is correct or even should be implemented for Interned<...>?
Add a small abstraction needed for decode to still re-intern Region and moved this along with other encode/decode implementations into a serialize file.

error[E0210]: type parameter `E` must be used as the type parameter for some local type (e.g., `MyStruct<E>`)
   --> compiler/rustc_middle/src/ty/codec.rs:162:12
    |
162 | impl<'tcx, E: TyEncoder<'tcx>> Encodable<E> for ty::Region<'tcx> {
    |            ^ type parameter `E` must be used as the type parameter for some local type
    |
    = note: implementing a foreign trait is only possible if at least one of the types for which it is implemented is local
    = note: only traits defined in the current crate can be implemented for a type parameter

error[E0210]: type parameter `D` must be used as the type parameter for some local type (e.g., `MyStruct<D>`)
   --> compiler/rustc_middle/src/ty/codec.rs:301:12
    |
301 | impl<'tcx, D: TyDecoder<'tcx>> Decodable<D> for ty::Region<'tcx> {
    |            ^ type parameter `D` must be used as the type parameter for some local type
    |
    = note: implementing a foreign trait is only possible if at least one of the types for which it is implemented is local
    = note: only traits defined in the current crate can be implemented for a type parameter

`compiler/rustc_middle/src/ty/region.rs`

Generally anything that needed to access fields on TyCtxt have been made methods on the interner.

interner.lifetimes.anon_re_bounds.get(debruijn.as_usize()) for getting an interned lifetime, is now a trait method on Interner; fn get_anon_re_bounds_lifetime(...)
fn intern_region(...) now a trait method on Interner
interner.lifetimes.anon_re_canonical_bounds.get(debruijn.as_usize()) required
for fn new_canonical_bound(...). Is now fn get_anon_re_canonical_bounds_lifetime(...)
interner.lifetimes.re_static has become fn get_re_static_lifetime() for method fn new_static((..)

r? @lcnr

rustbot · 2026-04-08T14:47:59Z

changes to the core type system

cc @lcnr

HIR ty lowering was modified

cc @fmease

Some changes occurred to MIR optimizations

cc @rust-lang/wg-mir-opt

lcnr · 2026-04-09T07:54:13Z

+        // Use a pre-interned one when possible.
+        if let BoundRegion { var, kind: BoundRegionKind::Anon } = bound_region
+            // This
+            && let Some(inner) = interner.get_anon_re_bounds_lifetime(debruijn.as_usize())


View changes since the review

i feel like these interning opts should not be in rustc_type_ir, so maybe add Interner::intern_bound_region and call that directly?

lcnr · 2026-04-09T07:54:18Z

+    #[inline]
+    pub fn new_canonical_bound(interner: I, var: BoundVar) -> Self {
+        // Use a pre-interned one when possible.
+        if let Some(re) = interner.get_anon_re_canonical_bounds_lifetime(var.as_usize()) {


View changes since the review

same here

lcnr

I don't fully get the changes to InternerDecoder

we should keep Region<I>: Display around by implementing it via IrPrint 🤔 having RegionDisplay seems unnecessary, we already have this IrPrint handling for other types, don't we?

IntoDiagArg is defined outside of rustc_middle? Maybe we should make it generic over I as well?

View changes since this review

lcnr · 2026-04-09T07:55:47Z

    Canonical,
 }

+impl<U: Interner> Lift<U> for BoundVarIndexKind {


surprising that this isn't/can't be derived or ignored in the derive

39c966a, by adding back nop_lift! { region; Region<'a> => Region<'tcx> } in compiler/rustc_middle/src/ty/context.rs it takes care of all of the comments about Lift

this impl still exists 🤔

still relevant

lcnr · 2026-04-09T07:56:37Z


 impl<I: Interner> Eq for RegionKind<I> {}

+impl<I: Interner, U: Interner> Lift<U> for RegionKind<I>


also not derived?

still relevant?

lcnr · 2026-04-09T08:06:56Z

For the pub struct Region if we use Interned<...> in the definition then we'd need to add a lifetime to the Interner trait. As such I opted for a type InternedRegionKind which is Interned<'tcx, RegionKind<'tcx>> in the implementation. To allow calling the kind() method I implemented inherent::IntoKind for Interned<'tcx, T>.

Interned itself is a type from rustc_middle anyways, is it not? 🤔 I would expect us to instead of type Interned<T> to trait Interner and have region be struct Region<I: Interner>(I::Interned<RegionKind>)

Had to implement Lift manually.

do we have some Lift_Generic derive or whatever? I feel like we should?

rustbot · 2026-04-09T10:19:13Z

Some changes occurred in src/tools/clippy

cc @rust-lang/clippy

rustbot · 2026-04-14T13:42:43Z

rust-analyzer is developed in its own repository. If possible, consider making this change to rust-lang/rust-analyzer instead.

cc @rust-lang/rust-analyzer

lcnr · 2026-07-21T09:18:23Z

-        }
+impl<'tcx, T: std::fmt::Debug + Clone + Copy> rustc_type_ir::intern::Interned<TyCtxt<'tcx>>
+    for Interned<'tcx, T>
+{


should not be in region as it applies to all interned things

View changes since the review

4bc330e 👍

lcnr · 2026-07-21T09:18:56Z

    Canonical,
 }

+impl<U: Interner> Lift<U> for BoundVarIndexKind {


still relevant

lcnr · 2026-07-21T09:20:52Z

+
+    fn lift_region_raw<I: Interner>(self, region: I::InternedRegionKind) -> Self::InternedRegionKind
+    where
+        I::InternedRegionKind: Lift<Self, Lifted = Self::InternedRegionKind>,


why do we need this instead of deriving Lift for Region (so that it just recursively lifts its field)

View changes since the review

ba50d0a 👍

lcnr · 2026-07-21T10:27:00Z


-    pub fn type_flags(self) -> TypeFlags {
+    fn type_flags(self) -> TypeFlags {
        let mut flags = TypeFlags::empty();


that method should be unused 🤔 more generally, rustc_type_ir duplicated some of the methods we also implement here, can you go through the methods on the extension trait and check whether we have the same method as an inherent method?

View changes since the review

5222b87 👍

lcnr · 2026-07-21T11:57:15Z

@bors r+ rollup=never

rust-bors · 2026-07-21T11:57:18Z

📌 Commit 2254fbc has been approved by lcnr

It is now in the queue for this repository.

JonathanBrouwer · 2026-07-21T13:52:47Z

@bors p=6
Schedulign

rust-bors · 2026-07-21T22:21:59Z

☀️ Test successful - CI
Approved by: lcnr
Duration: 3h 39m 10s
Pushing 0e29c21 to main...

github-actions · 2026-07-21T22:24:57Z

What is this?

This is an experimental post-merge analysis report that shows differences in test outcomes between the merged PR and its parent PR.

Comparing 79a4b00 (parent) -> 0e29c21 (this PR)

Test differences

Show 129 test diffs

129 doctest diffs were found. These are ignored, as they are noisy.

Test dashboard

Run

cargo run --manifest-path src/ci/citool/Cargo.toml -- \
    test-dashboard 0e29c21d93abc9bdc330182be1fbd33cfd5fee68 --output-dir test-dashboard

And then open test-dashboard/index.html in your browser to see an overview of all executed tests.

Job duration changes

aarch64-apple-macos-26: 2h 24m -> 3h 27m (+43.3%)
x86_64-gnu-miri: 1h 36m -> 1h 1m (-36.6%)
dist-ohos-x86_64: 58m 33s -> 1h 19m (+35.1%)
pr-check-1: 33m 46s -> 22m 15s (-34.1%)
x86_64-mingw-2: 2h 33m -> 1h 42m (-33.1%)
i686-gnu-1: 1h 51m -> 2h 26m (+31.8%)
x86_64-gnu-nopt: 2h 24m -> 1h 39m (-30.8%)
tidy: 2m 28s -> 1m 46s (-28.5%)
arm-android: 1h 41m -> 1h 13m (-27.9%)
dist-android: 28m 26s -> 20m 41s (-27.3%)

How to interpret the job duration changes?

Job durations can vary a lot, based on the actual runner instance
that executed the job, system noise, invalidated caches, etc. The table above is provided
mostly for t-infra members, for simpler debugging of potential CI slow-downs.

rust-timer · 2026-07-21T23:32:11Z

Finished benchmarking commit (0e29c21): comparison URL.

Overall result: no relevant changes - no action needed

@rustbot label: -perf-regression

Instruction count

This perf run didn't have relevant results for this metric.

Max RSS (memory usage)

Results (secondary -0.7%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	4.9%	[4.9%, 4.9%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-3.5%	[-5.6%, -1.4%]	2
All ❌✅ (primary)	-	-	0

Cycles

This perf run didn't have relevant results for this metric.

Binary size

This perf run didn't have relevant results for this metric.

Bootstrap: 489.717s -> 495.463s (1.17%)
Artifact size: 388.55 MiB -> 387.85 MiB (-0.18%)

rustbot assigned lcnr Apr 8, 2026

This comment has been minimized.

Sign in to view

lcnr reviewed Apr 9, 2026

View reviewed changes

Jamesbarford force-pushed the chore/move-region-to-ir branch from fc9ac0c to 39c966a Compare April 9, 2026 10:19

rustbot added the T-clippy Relevant to the Clippy team. label Apr 9, 2026

Jamesbarford force-pushed the chore/move-region-to-ir branch from 39c966a to 7c825ed Compare April 9, 2026 14:12

This comment has been minimized.

Sign in to view

Jamesbarford force-pushed the chore/move-region-to-ir branch from 6de045f to 89ecd54 Compare April 10, 2026 11:43

lcnr reviewed Apr 10, 2026

View reviewed changes

Comment thread compiler/rustc_middle/src/ty/context/impl_interner.rs

This comment has been minimized.

Sign in to view

Jamesbarford force-pushed the chore/move-region-to-ir branch from 89ecd54 to 706e15e Compare April 14, 2026 11:51

This comment has been minimized.

Sign in to view

rustbot added the T-rust-analyzer Relevant to the rust-analyzer team, which will review and decide on the PR/issue. label Apr 14, 2026

This comment has been minimized.

Sign in to view

lcnr reviewed Jul 21, 2026

View reviewed changes

Jamesbarford added 3 commits July 21, 2026 12:04

Move Region to rustc_type_ir

03a157a

Import extension traits and region

80d18b3

Import extension traits for clippy and rustdoc

2254fbc

Jamesbarford force-pushed the chore/move-region-to-ir branch from 5222b87 to 2254fbc Compare July 21, 2026 11:07

rust-bors Bot added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Jul 21, 2026

This comment has been minimized.

Sign in to view

rust-bors Bot added merged-by-bors This PR was explicitly merged by bors. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Jul 21, 2026

rust-bors Bot merged commit 0e29c21 into rust-lang:main Jul 21, 2026
14 checks passed

rustbot added this to the 1.99.0 milestone Jul 21, 2026

Jamesbarford deleted the chore/move-region-to-ir branch July 22, 2026 07:42

This was referenced Jul 22, 2026

Internal Tracking Issue for type system librarification #159654

Open

Stabilize the next-generation trait solver rust-lang/rust-project-goals#113

Open


		impl<I: Interner> Eq for RegionKind<I> {}

		impl<I: Interner, U: Interner> Lift<U> for RegionKind<I>

Uh oh!

Uh oh!

Conversation

Jamesbarford commented Apr 8, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

General notes

compiler/rustc_middle/src/ty/region.rs

Uh oh!

rustbot commented Apr 8, 2026

Uh oh!

This comment has been minimized.

This comment has been minimized.

This comment has been minimized.

lcnr Apr 9, 2026 • edited by rustbot Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

lcnr Apr 9, 2026 • edited by rustbot Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

lcnr left a comment • edited by rustbot Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Uh oh!

lcnr commented Apr 9, 2026

Uh oh!

rustbot commented Apr 9, 2026

Uh oh!

This comment has been minimized.

This comment has been minimized.

This comment has been minimized.

This comment has been minimized.

Uh oh!

This comment has been minimized.

This comment has been minimized.

rustbot commented Apr 14, 2026

Uh oh!

This comment has been minimized.

This comment has been minimized.

This comment has been minimized.

lcnr Jul 21, 2026 • edited by rustbot Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Choose a reason for hiding this comment

Uh oh!

lcnr Jul 21, 2026 • edited by rustbot Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

Jamesbarford Jul 21, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

lcnr Jul 21, 2026 • edited by rustbot Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Jamesbarford commented Apr 8, 2026 •

edited

Loading

`compiler/rustc_middle/src/ty/region.rs`

lcnr Apr 9, 2026 •

edited by rustbot

Loading

lcnr Apr 9, 2026 •

edited by rustbot

Loading

lcnr left a comment •

edited by rustbot

Loading

lcnr Jul 21, 2026 •

edited by rustbot

Loading

lcnr Jul 21, 2026 •

edited by rustbot

Loading

Jamesbarford Jul 21, 2026 •

edited

Loading

lcnr Jul 21, 2026 •

edited by rustbot

Loading