Clean up and speed up resolving code by jdonszelmann · Pull Request #160913 · rust-lang/rust

jdonszelmann · 2026-08-11T14:24:56Z

Clean up the resolve* family of functions in InferCtxt, renaming various functions to have more consistent and descriptive names. Adds a lot of documentation, and even wins some performance using the fact that shallow_resolve now returns root vids.

Reviewable commit by commit: some are large renames across the board, which are separated from the perf wins and small renames in other commits to hopefully make more sense.

Note

I've not used an LLM for any part of this PR, or any other PR I make. This includes any related work like research.

… tyvar.

rustbot · 2026-08-11T14:25:00Z

changes to inspect_obligations.rs

cc @lcnr

changes to the core type system

cc @lcnr

Some changes occurred in need_type_info.rs

cc @lcnr

Some changes occurred to the core trait solver

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

changes to the core type system

cc @lcnr

jdonszelmann · 2026-08-11T14:25:09Z

@bors try @rust-timer queue

Clean up and speed up resolving code

jdonszelmann · 2026-08-11T14:53:08Z

-        match self.inner.borrow_mut().type_variables().probe(vid) {
-            TypeVariableValue::Known { value } => Ok(value),
+        match value {
+            TypeVariableValue::Known { value } => Ok(self.shallow_resolve_non_recursive(value)),


this method (and the one below) now also does the recursive resolving shallow_resolve already did. No tests change here.

View changes since the review

jdonszelmann · 2026-08-11T14:53:33Z

+    // Cold because the case in which a tyvar resolves to an intvar which resolves to a type is
+    // quite rare. It's way more common for `shallow_resolve_non_recursive` to return ty.
+    #[cold]
+    fn shallow_resolve_infer_non_recursive(&self, infer: InferTy, ty: Ty<'tcx>) -> Ty<'tcx> {


the non-recursive caase helps ~0.5% on local benchmarks. Not much, but still a bit.

View changes since the review

jdonszelmann · 2026-08-11T14:57:58Z

            }

            ty::Infer(ty::IntVar(vid)) => {
-                let nt = self.infcx.unwrap().opportunistic_resolve_int_var(vid);


renames all the opportunistic_* functions with simply shallow_resolve_*. I've done this in many places. I've added a lot of docs to all the resolve methods, which I think makes it super clear that resolving is always an opportunistic process that doesn't necessarily resolve all variables, simply because it can't always.

From the perspective of a new contributor, they'll see a resolve_* function for the first time, go to its docs, and learn that the purpose of all resolve_* methods is to opportunistically resolve variables.

Since the behavior is the same for all the resolve_* functions I think that will actually make things clearer than randomly calling some of them "opportunistic" even when the others are inherently also opportunistic.

View changes since the review

jdonszelmann · 2026-08-11T14:59:06Z

+    /// In cases where we do, this can aid performance.
    #[inline(always)]
-    fn shallow_resolve_ty_var(&self, v: TyVid, ty: Ty<'tcx>) -> Ty<'tcx> {
+    fn shallow_resolve_ty_var_with_ty(&self, v: TyVid, ty: Option<Ty<'tcx>>) -> Ty<'tcx> {


By taking an Option here, we can merge more methods' implementations. Doing this has 0 performance overhead, #[inline(always)] makes sure the callsites that always call with Some get optimized properly.

View changes since the review

rust-bors · 2026-08-11T15:25:32Z

💔 Test for 7e8d4ec failed: CI. Failed job:

try - dist-x86_64-linux-quick (web logs, enhanced plaintext logs)

…er a shallow_resolve

jdonszelmann · 2026-08-11T15:47:37Z

@bors try (failed due to missing rustdoc changes now applied)

rust-bors · 2026-08-11T15:47:41Z

Unknown argument "(failed". Did you mean to use @bors jobs=<jobs>|parent=<parent>? Run @bors help or go to https://bors.rust-lang.org/help to see available commands.

rust-log-analyzer · 2026-08-11T15:56:12Z

The job tidy failed! Check out the build log: (web) (plain enhanced) (plain)

Click to see the possible cause of the failure (guessed by this bot)

#14 3.278 Building wheels for collected packages: reuse
#14 3.279   Building wheel for reuse (pyproject.toml): started
#14 3.475   Building wheel for reuse (pyproject.toml): finished with status 'done'
#14 3.476   Created wheel for reuse: filename=reuse-4.0.3-cp310-cp310-manylinux_2_35_x86_64.whl size=132857 sha256=6a78a69541e3df9c7c106367722bab90241125ee6b7cdb81c5e40637268f85a9
#14 3.477   Stored in directory: /tmp/pip-ephem-wheel-cache-mc3geqtt/wheels/3d/8d/0a/e0fc6aba4494b28a967ab5eaf951c121d9c677958714e34532
#14 3.479 Successfully built reuse
#14 3.479 Installing collected packages: boolean-py, binaryornot, tomlkit, reuse, python-debian, markupsafe, license-expression, jinja2, chardet, attrs
#14 3.924 Successfully installed attrs-23.2.0 binaryornot-0.4.4 boolean-py-4.0 chardet-5.2.0 jinja2-3.1.4 license-expression-30.3.0 markupsafe-2.1.5 python-debian-0.1.49 reuse-4.0.3 tomlkit-0.13.0
#14 3.924 WARNING: Running pip as the 'root' user can result in broken permissions and conflicting behaviour with the system package manager. It is recommended to use a virtual environment instead: https://pip.pypa.io/warnings/venv
#14 4.455 Collecting virtualenv
---
     ╭▸ compiler/rustc_infer/src/infer/mod.rs:1409:42
     │
1409 │     ///   type, then this set of equated varibles forms an equivalence class. One of the variables
     ╰╴                                         ━━━━━━━━
rerun with `--bless` to fix typos: `./x.py test tidy --extra-checks=spellcheck --bless`
tidy [extra_checks:spellcheck]: checks with external tool 'typos' failed
tidy [extra_checks:spellcheck]: FAIL
yarn install v1.22.22
warning package.json: No license field
warning ../../package.json: License should be a valid SPDX license expression
warning No license field
[1/4] Resolving packages...
---
Running eslint on rustdoc JS files
info: ES-Check: checking 7 files...
info: ✓ ES-Check passed! All files are ES10 compatible.
typechecking javascript files
tidy: The following check failed: extra_checks:spellcheck
Bootstrap failed while executing `test src/tools/tidy tidyselftest --extra-checks=py,cpp,js,spellcheck`
Currently active steps:
test::Tidy {  } at src/bootstrap/src/core/build_steps/test.rs:1641
Command `/checkout/obj/build/x86_64-unknown-linux-gnu/stage1-tools-bin/rust-tidy --root-path=/checkout --cargo-path=/checkout/obj/build/x86_64-unknown-linux-gnu/stage0/bin/cargo --output-dir=/checkout/obj/build --concurrency=4 --npm-path=/node/bin/yarn --ci=true --extra-checks=py,cpp,js,spellcheck` failed with exit code 1
Created at: src/bootstrap/src/core/build_steps/tool.rs:1608:23
Executed at: src/bootstrap/src/core/build_steps/test.rs:1723:29

Command has failed. Rerun with -v to see more details.
Build completed unsuccessfully in 0:02:24
  local time: Tue Aug 11 15:55:59 UTC 2026
  network time: Tue, 11 Aug 2026 15:55:59 GMT
##[error]Process completed with exit code 1.
##[group]Run echo "disk usage:"

panstromek · 2026-08-11T16:49:37Z

@bors try

Clean up and speed up resolving code

rust-bors · 2026-08-11T17:49:20Z

☀️ Try build successful (CI)
Build commit: d881e22 (d881e228b79422918a125ef8385170091369309b)
Base parent: a04c7a0 (a04c7a037d59b6dedc9f921e84e391f13a257aa4)

rust-timer · 2026-08-11T18:37:34Z

Finished benchmarking commit (d881e22): comparison URL.

Overall result: ✅ improvements - no action needed

Benchmarking means the PR may be perf-sensitive. It's automatically marked not fit for rolling up. Overriding is possible but disadvised: it risks changing compiler perf.

@bors rollup=never rustc-perf
@rustbot label: -S-waiting-on-perf -perf-regression

Instruction count

Our most reliable metric. Used to determine the overall result above. However, even this metric can be noisy.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.2%	[-0.4%, -0.1%]	34
Improvements ✅ (secondary)	-0.5%	[-1.2%, -0.2%]	39
All ❌✅ (primary)	-0.2%	[-0.4%, -0.1%]	34

Max RSS (memory usage)

Results (primary 5.7%, 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)	5.7%	[5.1%, 6.3%]	2
Regressions ❌ (secondary)	0.6%	[0.6%, 0.6%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.8%	[-3.0%, -0.4%]	10
All ❌✅ (primary)	5.7%	[5.1%, 6.3%]	2

Cycles

Results (primary 2.5%, secondary 0.4%)

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

	mean	range	count
Regressions ❌ (primary)	2.5%	[2.5%, 2.5%]	1
Regressions ❌ (secondary)	0.8%	[0.4%, 1.5%]	8
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.9%	[-1.6%, -0.5%]	3
All ❌✅ (primary)	2.5%	[2.5%, 2.5%]	1

Binary size

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

Bootstrap: 463.191s -> 456.07s (-1.54%)
Artifact size: 396.43 MiB -> 396.43 MiB (-0.00%)

rust-bors · 2026-08-11T22:19:17Z

☔ The latest upstream changes (presumably #158436) made this pull request unmergeable. Please resolve the merge conflicts by rebasing.

jdonszelmann · 2026-08-11T23:37:54Z

that seems worth it :3

jdonszelmann added 5 commits August 11, 2026 16:16

optimize resolve, and properly document the related methods

a67ed41

unify implementations of shallow_resolve and opportunistic_resolve

adda255

Make region methods consistent and faster.

7c8b90a

Make const methods consistent and expose methods to shallow resolve a…

d6dc475

… tyvar.

expose the same through inferctxlike

bea827e

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 Aug 11, 2026

rustbot assigned lcnr Aug 11, 2026

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rust-bors Bot pushed a commit that referenced this pull request Aug 11, 2026

Auto merge of #160913 - jdonszelmann:cleanup-resolving, r=<try>

7e8d4ec

Clean up and speed up resolving code

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jdonszelmann force-pushed the cleanup-resolving branch from 3dde145 to b5fe24d Compare August 11, 2026 14:45

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jdonszelmann commented Aug 11, 2026

View reviewed changes

rust-bors Bot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Aug 11, 2026

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jdonszelmann added 3 commits August 11, 2026 17:41

rename resolver folders and their access functions

5b04d20

make lifetime methods more consistent

64a0e81

fixup various sites that use root_{ty,const}_var that can skip it aft…

6b88c26

…er a shallow_resolve

jdonszelmann force-pushed the cleanup-resolving branch from b5fe24d to 6b88c26 Compare August 11, 2026 15:47

rustbot added the T-rustdoc-frontend Relevant to the rustdoc-frontend team, which will review and decide on the web UI/UX output. label Aug 11, 2026

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rust-bors Bot pushed a commit that referenced this pull request Aug 11, 2026

Auto merge of #160913 - jdonszelmann:cleanup-resolving, r=<try>

d881e22

Clean up and speed up resolving code

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rustbot removed the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Aug 11, 2026

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rust-timer commented Aug 11, 2026

Overall result: ✅ improvements - no action needed

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