Next steps for FnDef binder changes (instantiate most FnDef binders) by addiesh · Pull Request #159403 · rust-lang/rust

addiesh · 2026-07-16T16:48:59Z

This change is a part of the ongoing effort to clean up binder/turbofishing behavior in the compiler (#156581).

This PR instantiates binders that were previously created via ty::Binder::dummy() with meaningfully bound vars.

r? oli-obk

Call me Turbofishmael.
Some years ago- never mind how long precisely-
having little or no money in my purse,
and nothing particular to interest me in C++,
I thought I would sail about a little and see the rusty part of the world.

rustbot · 2026-07-16T16:49:05Z

Thanks for the pull request, and welcome! The Rust Project is excited to review your changes, and you should hear from @oli-obk (or someone else) some time within the next two weeks.

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Next steps for FnDef binder changes (instantiate most FnDef binders)

Replace most `Ty::new_fn_def` calls with `type_of` queries directly This is so we can reduce the amount of code and changes in rust-lang#159403. It should stand on its own, but really it's meant as an extended part of 159403. This allows getting the right `ty::FnDef` even cross-crate, as the `type_of` query results are stored in metadata, in contrast to the queries for computing the binder for various declarations. These binders are already cached via `fn_sig`, but using that is somewhat overkill and can cause cycle errors in some cases.

rust-bors · 2026-07-28T18:49:44Z

☀️ Try build successful (CI)
Build commit: e543d43 (e543d43122dcbf198ae8b3f808a8c2bf1593e979)
Base parent: e19d321 (e19d321c06479c6fd77533582b0d5a86651f1be3)

Replace most `Ty::new_fn_def` calls with `type_of` queries directly This is so we can reduce the amount of code and changes in rust-lang#159403. It should stand on its own, but really it's meant as an extended part of 159403. This allows getting the right `ty::FnDef` even cross-crate, as the `type_of` query results are stored in metadata, in contrast to the queries for computing the binder for various declarations. These binders are already cached via `fn_sig`, but using that is somewhat overkill and can cause cycle errors in some cases.

rust-timer · 2026-07-28T19:31:37Z

Finished benchmarking commit (e543d43): comparison URL.

Overall result: ❌✅ regressions and improvements - please read:

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.

Next, please: If you can, justify the regressions found in this try perf run in writing along with @rustbot label: +perf-regression-triaged. If not, fix the regressions and do another perf run. Neutral or positive results will clear the label automatically.

@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)	0.3%	[0.2%, 0.4%]	18
Regressions ❌ (secondary)	0.3%	[0.1%, 0.5%]	10
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.5%	[-0.9%, -0.1%]	3
All ❌✅ (primary)	0.3%	[0.2%, 0.4%]	18

Max RSS (memory usage)

Results (primary 1.0%, secondary 1.6%)

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

	mean	range	count
Regressions ❌ (primary)	1.0%	[0.8%, 1.7%]	5
Regressions ❌ (secondary)	3.4%	[2.3%, 4.5%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.0%	[-2.0%, -2.0%]	1
All ❌✅ (primary)	1.0%	[0.8%, 1.7%]	5

Cycles

Results (primary -1.3%, secondary -3.1%)

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)	4.0%	[4.0%, 4.0%]	1
Improvements ✅ (primary)	-1.3%	[-1.3%, -1.3%]	1
Improvements ✅ (secondary)	-4.5%	[-6.1%, -3.1%]	5
All ❌✅ (primary)	-1.3%	[-1.3%, -1.3%]	1

Binary size

Results (primary 0.2%, secondary 0.3%)

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

	mean	range	count
Regressions ❌ (primary)	0.2%	[0.0%, 0.5%]	83
Regressions ❌ (secondary)	0.3%	[0.0%, 1.0%]	56
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.2%	[0.0%, 0.5%]	83

Bootstrap: 490.165s -> 490.514s (0.07%)
Artifact size: 388.34 MiB -> 391.03 MiB (0.69%)

Rollup merge of #159665 - addiesh:turbofish-fear-me, r=oli-obk Replace most `Ty::new_fn_def` calls with `type_of` queries directly This is so we can reduce the amount of code and changes in #159403. It should stand on its own, but really it's meant as an extended part of 159403. This allows getting the right `ty::FnDef` even cross-crate, as the `type_of` query results are stored in metadata, in contrast to the queries for computing the binder for various declarations. These binders are already cached via `fn_sig`, but using that is somewhat overkill and can cause cycle errors in some cases.

rustbot · 2026-07-29T00:29:02Z

Some changes occurred to the core trait solver

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

Some changes occurred in compiler/rustc_passes/src/check_attr.rs

cc @jdonszelmann, @JonathanBrouwer

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

cc @BoxyUwU, @tshepang

Some changes occurred in coverage instrumentation.

cc @Zalathar

Some changes occurred in compiler/rustc_attr_parsing

cc @jdonszelmann, @JonathanBrouwer

These commits modify the Cargo.lock file. Unintentional changes to Cargo.lock can be introduced when switching branches and rebasing PRs.

If this was unintentional then you should revert the changes before this PR is merged.
Otherwise, you can ignore this comment.

miri is developed in its own repository. If the Miri part of this change can be broken out, consider making this change to rust-lang/miri instead. However, if Miri needs adjusting for rustc changes, just ignore this message.

cc @rust-lang/miri

Some changes occurred to the CTFE / Miri interpreter

cc @rust-lang/miri

This PR changes rustc_public

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

Some changes occurred to the CTFE machinery

cc @RalfJung, @oli-obk, @lcnr

The parser was modified, potentially altering the grammar of (stable) Rust
which would be a breaking change.

cc @fmease

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

cc @antoyo, @GuillaumeGomez

Some changes occurred in GUI tests.

cc @GuillaumeGomez

Some changes occurred to diagnostic attributes.

cc @mejrs

changes to the core type system

cc @lcnr

This PR modifies bootstrap.example.toml.

If appropriate, please update CONFIG_CHANGE_HISTORY in src/bootstrap/src/utils/change_tracker.rs.

Some changes occurred in const_evaluatable.rs

cc @BoxyUwU

Some changes occurred in compiler/rustc_hir/src/attrs

cc @jdonszelmann, @JonathanBrouwer

rustbot · 2026-07-29T14:33:09Z

This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

addiesh · 2026-07-20T15:51:53Z

this """"fixed"""" issue #133613, but the errors are absolutely nasty and it uses experimental features. This is worth checking out.

View changes since the review

rustbot assigned oli-obk Jul 16, 2026

addiesh force-pushed the call-me-turbofishmael branch 3 times, most recently from 014b214 to d780036 Compare July 16, 2026 19:40