delegation: refactor AST -> HIR lowering by aerooneqq · Pull Request #158434 · rust-lang/rust

aerooneqq · 2026-06-26T08:41:06Z

After a lot of new features were added to delegation the code became a bit worse, as resolution and lowering logic is mixed in delegation.rs. In this file the output of resolution step of delegation is transferred as function params (in some functions up to 7 or 8 params), which is not good looking for me.

As I mentioned in the previous paragraph delegation AST -> HIR lowering can be split into two phases:

Resolution - we collect all information about signature, signature parent context, delegation parent, delegation generics. Then this information is used in AST -> HIR lowering,
AST -> HIR lowering - we generate everything based on the output of resolution.

This PR explicitly splits those two phases: as a first step we collect all needed information into DelegationResolution struct and then use it during AST -> HIR lowering. The delegation.rs file is moved into delegation folder and renamed to mod.rs, the final file structure is as follows:

mod.rs - contains lowering logic for everything but generics,
generics.rs - contains logic for resolution and uplifting of generic params, placed in a separate file as it is a significant and independent part of lowering,
attributes.rs - contains relatively small piece of logic which connects to attributes inheritance,
resolution.rs - contains logic for resolution of everything but generics.

As resolution of delegation and generics logically does not depend on LoweringContext, as from its name LoweringContext contains many additional information which is used for lowering, I've created LoweringContextForResolution trait which abstracts operations which are used during delegation resolution.

Benefits of this PR:

Resolution information is grouped into single struct, is extracted from AST -> HIR lowering which leads to better transfer of resolution across lowering (through a single struct, not through many arguments) and enhanced understanding of which information we use for delegation lowering,
There is now a single path for generating error delegation - if an error was returned from delegation resolution,
Refactorings of uplift_delegation_generics which was creating generic params for delegation made the code more understandable.

Part of #118212.
r? @petrochenkov

aerooneqq · 2026-06-26T08:42:08Z

Now this PR is based on #158397, so it is draft until #158397 is merged, but feedback is anyway welcomed.

petrochenkov · 2026-07-02T10:58:02Z

Could you split this into 2 commits - one moving code around (to different files, or within files), and the second one doing the code changes/refactorings?
@rustbot author

rustbot · 2026-07-02T10:58:06Z

Reminder, once the PR becomes ready for a review, use @rustbot ready.

aerooneqq · 2026-07-02T11:12:11Z

@rustbot ready

aerooneqq · 2026-07-02T12:59:35Z

@rustbot ready

petrochenkov · 2026-07-02T13:24:16Z

r=me after addressing the remaining comments and squashing the refactoring commits.
@rustbot author
@bors delegate+

rust-bors · 2026-07-02T13:24:20Z

✌️ @aerooneqq, you can now approve this pull request!

If @petrochenkov told you to "r=me" after making some further change, then please make that change and post @bors r=petrochenkov.

View changes since this delegation.

aerooneqq · 2026-07-02T20:33:22Z

@bors r=petrochenkov

rust-bors · 2026-07-02T20:33:26Z

📌 Commit d42cca5 has been approved by petrochenkov

It is now in the queue for this repository.

🌲 The tree is currently closed for pull requests below priority 10. This pull request will be tested once the tree is reopened.

@petrochenkov

…r=petrochenkov delegation: refactor AST -> HIR lowering After a lot of new features were added to delegation the code became a bit worse, as resolution and lowering logic is mixed in `delegation.rs`. In this file the output of resolution step of delegation is transferred as function params (in some functions up to 7 or 8 params), which is not good looking for me. As I mentioned in the previous paragraph delegation AST -> HIR lowering can be split into two phases: 1. Resolution - we collect all information about signature, signature parent context, delegation parent, delegation generics. Then this information is used in AST -> HIR lowering, 2. AST -> HIR lowering - we generate everything based on the output of resolution. This PR explicitly splits those two phases: as a first step we collect all needed information into `DelegationResolution` struct and then use it during AST -> HIR lowering. The `delegation.rs` file is moved into `delegation` folder and renamed to `mod.rs`, the final file structure is as follows: - `mod.rs` - contains lowering logic for everything but generics, - `generics.rs` - contains logic for resolution and uplifting of generic params, placed in a separate file as it is a significant and independent part of lowering, - `attributes.rs` - contains relatively small piece of logic which connects to attributes inheritance, - `resolution.rs` - contains logic for resolution of everything but generics. As resolution of delegation and generics logically does not depend on `LoweringContext`, as from its name `LoweringContext` contains many additional information which is used for lowering, I've created `LoweringContextForResolution` trait which abstracts operations which are used during delegation resolution. Benefits of this PR: - Resolution information is grouped into single struct, is extracted from AST -> HIR lowering which leads to better transfer of resolution across lowering (through a single struct, not through many arguments) and enhanced understanding of which information we use for delegation lowering, - There is now a single path for generating error delegation - if an error was returned from delegation resolution, - Refactorings of `uplift_delegation_generics` which was creating generic params for delegation made the code more understandable. Part of rust-lang#118212. r? @petrochenkov

Rollup of 18 pull requests Successful merges: - #158692 (Add release notes for 1.96.1) - #134021 (Implement `IntoIterator` for `[&[mut]] Box<[T; N], A>`) - #152860 (Port the `without_debuginfo` test from `backtrace-rs` to the testsuite) - #155932 (MIR Call terminator: evaluate destination place before arguments) - #156777 (Add -Zautodiff_post_passes flag to limit which llvm passes to run after enzyme to make autodiff tests more robust) - #157151 (JSON target specs: remove 'x86-softfloat' compatibility alias) - #157835 (expand free alias types in the auto-trait orphan check) - #158377 (add `-Zforce-intrinsic-fallback` flag) - #158434 (delegation: refactor AST -> HIR lowering) - #158552 (make some tidy errors around python easier to understand) - #158624 (borrowck: Introduce BlameConstraint::to_obligation_cause_from_path()) - #158704 (Optimize `ArrayChunks::try_rfold` with `DoubleEndedIterator::next_chunk_back`) - #158711 (library: Comment on libtest's dicey internal soundness) - #158539 (Move `SizeHint` and `IoHandle` to `core::io`) - #158659 (refactor the normalization in `coerce_shared_info`) - #158689 (resolver: don't use `Finalize` when resolving visibilities during AST expansion) - #158698 (Update TypeVisitable implementation) - #158706 (Tweaks to MIR building scope API)

@petrochenkov

…r=petrochenkov delegation: refactor AST -> HIR lowering After a lot of new features were added to delegation the code became a bit worse, as resolution and lowering logic is mixed in `delegation.rs`. In this file the output of resolution step of delegation is transferred as function params (in some functions up to 7 or 8 params), which is not good looking for me. As I mentioned in the previous paragraph delegation AST -> HIR lowering can be split into two phases: 1. Resolution - we collect all information about signature, signature parent context, delegation parent, delegation generics. Then this information is used in AST -> HIR lowering, 2. AST -> HIR lowering - we generate everything based on the output of resolution. This PR explicitly splits those two phases: as a first step we collect all needed information into `DelegationResolution` struct and then use it during AST -> HIR lowering. The `delegation.rs` file is moved into `delegation` folder and renamed to `mod.rs`, the final file structure is as follows: - `mod.rs` - contains lowering logic for everything but generics, - `generics.rs` - contains logic for resolution and uplifting of generic params, placed in a separate file as it is a significant and independent part of lowering, - `attributes.rs` - contains relatively small piece of logic which connects to attributes inheritance, - `resolution.rs` - contains logic for resolution of everything but generics. As resolution of delegation and generics logically does not depend on `LoweringContext`, as from its name `LoweringContext` contains many additional information which is used for lowering, I've created `LoweringContextForResolution` trait which abstracts operations which are used during delegation resolution. Benefits of this PR: - Resolution information is grouped into single struct, is extracted from AST -> HIR lowering which leads to better transfer of resolution across lowering (through a single struct, not through many arguments) and enhanced understanding of which information we use for delegation lowering, - There is now a single path for generating error delegation - if an error was returned from delegation resolution, - Refactorings of `uplift_delegation_generics` which was creating generic params for delegation made the code more understandable. Part of rust-lang#118212. r? @petrochenkov

…uwer Rollup of 20 pull requests Successful merges: - #158692 (Add release notes for 1.96.1) - #134021 (Implement `IntoIterator` for `[&[mut]] Box<[T; N], A>`) - #155932 (MIR Call terminator: evaluate destination place before arguments) - #155989 (Update `transmute_copy` to ub_checks and `?Sized`) - #156777 (Add -Zautodiff_post_passes flag to limit which llvm passes to run after enzyme to make autodiff tests more robust) - #157151 (JSON target specs: remove 'x86-softfloat' compatibility alias) - #157835 (expand free alias types in the auto-trait orphan check) - #157857 (Stabilize `#[my_macro] mod foo;` (part of `proc_macro_hygiene`)) - #158377 (add `-Zforce-intrinsic-fallback` flag) - #158434 (delegation: refactor AST -> HIR lowering) - #158552 (make some tidy errors around python easier to understand) - #158624 (borrowck: Introduce BlameConstraint::to_obligation_cause_from_path()) - #158704 (Optimize `ArrayChunks::try_rfold` with `DoubleEndedIterator::next_chunk_back`) - #158711 (library: Comment on libtest's dicey internal soundness) - #158751 (rustdoc: Fix crash when trying to inline foreign item which cannot have attributes) - #158539 (Move `SizeHint` and `IoHandle` to `core::io`) - #158659 (refactor the normalization in `coerce_shared_info`) - #158689 (resolver: don't use `Finalize` when resolving visibilities during AST expansion) - #158698 (Update TypeVisitable implementation) - #158706 (Tweaks to MIR building scope API)

@petrochenkov

…r=petrochenkov delegation: refactor AST -> HIR lowering After a lot of new features were added to delegation the code became a bit worse, as resolution and lowering logic is mixed in `delegation.rs`. In this file the output of resolution step of delegation is transferred as function params (in some functions up to 7 or 8 params), which is not good looking for me. As I mentioned in the previous paragraph delegation AST -> HIR lowering can be split into two phases: 1. Resolution - we collect all information about signature, signature parent context, delegation parent, delegation generics. Then this information is used in AST -> HIR lowering, 2. AST -> HIR lowering - we generate everything based on the output of resolution. This PR explicitly splits those two phases: as a first step we collect all needed information into `DelegationResolution` struct and then use it during AST -> HIR lowering. The `delegation.rs` file is moved into `delegation` folder and renamed to `mod.rs`, the final file structure is as follows: - `mod.rs` - contains lowering logic for everything but generics, - `generics.rs` - contains logic for resolution and uplifting of generic params, placed in a separate file as it is a significant and independent part of lowering, - `attributes.rs` - contains relatively small piece of logic which connects to attributes inheritance, - `resolution.rs` - contains logic for resolution of everything but generics. As resolution of delegation and generics logically does not depend on `LoweringContext`, as from its name `LoweringContext` contains many additional information which is used for lowering, I've created `LoweringContextForResolution` trait which abstracts operations which are used during delegation resolution. Benefits of this PR: - Resolution information is grouped into single struct, is extracted from AST -> HIR lowering which leads to better transfer of resolution across lowering (through a single struct, not through many arguments) and enhanced understanding of which information we use for delegation lowering, - There is now a single path for generating error delegation - if an error was returned from delegation resolution, - Refactorings of `uplift_delegation_generics` which was creating generic params for delegation made the code more understandable. Part of rust-lang#118212. r? @petrochenkov

rustbot assigned petrochenkov Jun 26, 2026

rustbot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Jun 26, 2026

This comment has been minimized.

Sign in to view

aerooneqq force-pushed the delegation-refactoring branch from d6dd2be to c2d7c9c Compare June 29, 2026 12:03

This comment has been minimized.

Sign in to view

aerooneqq force-pushed the delegation-refactoring branch from ae9c536 to faa250b Compare July 1, 2026 06:56

This comment has been minimized.

Sign in to view

aerooneqq force-pushed the delegation-refactoring branch from faa250b to 002fc94 Compare July 2, 2026 05:42

aerooneqq marked this pull request as ready for review July 2, 2026 05:45

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Jul 2, 2026

petrochenkov added the F-fn_delegation `#![feature(fn_delegation)]` label Jul 2, 2026

rustbot removed the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jul 2, 2026

rustbot added the S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. label Jul 2, 2026

aerooneqq force-pushed the delegation-refactoring branch from 67f05b8 to 2196005 Compare July 2, 2026 11:11

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Jul 2, 2026

aerooneqq mentioned this pull request Jul 2, 2026

delegation: support mapping of all arguments with Self type #158690

Draft

petrochenkov reviewed Jul 2, 2026

View reviewed changes

petrochenkov 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 Jul 2, 2026

rustbot removed the S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. label Jul 2, 2026

rustbot added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jul 2, 2026

aerooneqq commented Jul 2, 2026

View reviewed changes

Comment thread compiler/rustc_ast_lowering/src/delegation/resolution.rs Outdated

petrochenkov reviewed Jul 2, 2026

View reviewed changes

Comment thread compiler/rustc_ast_lowering/src/delegation/resolution.rs Outdated

Comment thread compiler/rustc_ast_lowering/src/delegation/resolution.rs Outdated

Comment thread compiler/rustc_ast_lowering/src/delegation/generics.rs Outdated

rustbot removed the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jul 2, 2026

rustbot added the S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. label Jul 2, 2026

This comment has been minimized.

Sign in to view

Refactor delegation AST -> HIR lowering

d42cca5

aerooneqq force-pushed the delegation-refactoring branch from aec2af7 to d42cca5 Compare July 2, 2026 19:40

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 2, 2026

jhpratt mentioned this pull request Jul 3, 2026

Rollup of 18 pull requests #158753

Closed

JonathanBrouwer mentioned this pull request Jul 5, 2026

Rollup of 20 pull requests #158798

Closed

JonathanBrouwer mentioned this pull request Jul 5, 2026

Rollup of 19 pull requests #158811

Open

Uh oh!

Uh oh!

Conversation

aerooneqq commented Jun 26, 2026 • edited by rustbot Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

aerooneqq commented Jun 26, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

This comment has been minimized.

This comment has been minimized.

This comment has been minimized.

This comment has been minimized.

This comment has been minimized.

petrochenkov commented Jul 2, 2026

Uh oh!

rustbot commented Jul 2, 2026

Uh oh!

aerooneqq commented Jul 2, 2026

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

aerooneqq commented Jul 2, 2026

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

petrochenkov commented Jul 2, 2026

Uh oh!

rust-bors Bot commented Jul 2, 2026

Uh oh!

This comment has been minimized.

aerooneqq commented Jul 2, 2026

Uh oh!

rust-bors Bot commented Jul 2, 2026

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

4 participants

aerooneqq commented Jun 26, 2026 •

edited by rustbot

Loading

aerooneqq commented Jun 26, 2026 •

edited

Loading