bootstrap: Split the `Step` trait into multiple traits by Zalathar · Pull Request #159638 · rust-lang/rust

Zalathar · 2026-07-21T07:05:31Z

An awkward thing about bootstrap's Step trait is that several of its implementations represent “helper tasks” that participate in bootstrap's internal caching system, but can't be explicitly selected via command-line arguments. Those tasks need to supply dummy implementations for some Step methods related to command-line processing.

This PR tries to reduce that tension by splitting the Step trait into two traits.

Steps that can be selected from the command-line implement the full CommandLineStep trait, which also provides an implementation of Step.

Helper tasks implement the smaller Step trait directly. They still participate in step-caching and step-tracing, but don't interact with command-line selectors.

r? jieyouxu

rustbot · 2026-07-21T07:05:35Z

This PR changes how LLVM is built. Consider updating src/bootstrap/download-ci-llvm-stamp.

This PR changes how GCC is built. Consider updating src/bootstrap/download-ci-gcc-stamp.

Kobzol

I'm fine with the CommandLineStep, is is very clear in what it does :)

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Zalathar · 2026-07-23T02:35:50Z

(Rebased over import conflicts, no changes.)

jieyouxu

Thanks! r=me after two tiny nits
@rustbot author

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rustbot · 2026-07-25T14:26:27Z

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.

Steps that can be selected from the command-line implement the full `CommandLineStep` trait, which also provides an implementation of `Step`. Helper tasks implement the smaller `Step` trait directly. They still participate in step-caching and step-tracing, but don't interact with command-line selectors.

Zalathar · 2026-07-26T03:10:47Z

Addressed nits: (diff)

Zalathar · 2026-07-26T03:13:15Z

@bors r=jieyouxu

rust-bors · 2026-07-26T03:13:17Z

📌 Commit 7b3e992 has been approved by jieyouxu

It is now in the queue for this repository.

🌲 The tree is currently closed for pull requests below priority 100. This pull request will be tested once the tree is reopened.

Reason for tree closure: spurious failures

bootstrap: Split the `Step` trait into multiple traits - Revised version of rust-lang#159423 - [#t-infra/bootstrap > Terminology consistency of the important concepts](https://rust-lang.zulipchat.com/#narrow/channel/326414-t-infra.2Fbootstrap/topic/Terminology.20consistency.20of.20the.20important.20concepts/with/611795947) - [#t-infra/bootstrap > Path filters in bootstrap](https://rust-lang.zulipchat.com/#narrow/channel/326414-t-infra.2Fbootstrap/topic/Path.20filters.20in.20bootstrap/with/611415742) --- An awkward thing about bootstrap's Step trait is that several of its implementations represent “helper tasks” that participate in bootstrap's internal caching system, but can't be explicitly selected via command-line arguments. Those tasks need to supply dummy implementations for some Step methods related to command-line processing. This PR tries to reduce that tension by splitting the `Step` trait into two traits. --- Steps that can be selected from the command-line implement the full `CommandLineStep` trait, which also provides an implementation of `Step`. Helper tasks implement the smaller `Step` trait directly. They still participate in step-caching and step-tracing, but don't interact with command-line selectors. r? jieyouxu

…uwer Rollup of 24 pull requests Successful merges: - #159638 (bootstrap: Split the `Step` trait into multiple traits) - #159774 (rustc_trait_selection: fix trait solver hang caused by degenerate obligations) - #159837 (line-tables-only test: check that the line number matches the function name) - #159946 (Update Enzyme submodule to imporve llvm-cov) - #159617 (Fix up `#[linkage]` target checking) - #159733 (std: Switch implementations of `thread_local!` for WASI) - #159783 (Check unsafe impls on safe EIIs) - #159810 (Add tuple never coercion collection regression test) - #159821 (Update expect message using the recommended style in binary_heap module) - #159826 (Remove redundant `#[rustc_paren_sugar]` feature gate) - #159846 (Implement `str::copy_from_str`) - #159849 (rustc_parse: Stop returning `Option` from statement parsing) - #159853 (Updated expect messages for `CString` struct and method documentation) - #159875 (More cleanup in `rustc_attr_parsing`) - #159882 (Update expect messages in library/alloc/boxed.rs and library/alloc/string.rs to follow the style guide) - #159891 (Split multiline derives into std/rustc macros) - #159893 (Fix `find_attr` hygiene and `rustc_hir` cleanups) - #159895 (rustc-dev-guide subtree update) - #159902 (Clarify that the expected runtime symbols signature is for the current target only) - #159914 (Fix error in diagnostic on_unmatched_args) - #159917 (spare capacity mut constification) - #159918 (rename abort_unwind → abort_on_unwind) - #159936 (Minor `rustc_ast::ast` doc cleanups) - #159945 (Update expect messages in library/core/src/ptr/non_null.rs)

bootstrap: Split the `Step` trait into multiple traits - Revised version of rust-lang#159423 - [#t-infra/bootstrap > Terminology consistency of the important concepts](https://rust-lang.zulipchat.com/#narrow/channel/326414-t-infra.2Fbootstrap/topic/Terminology.20consistency.20of.20the.20important.20concepts/with/611795947) - [#t-infra/bootstrap > Path filters in bootstrap](https://rust-lang.zulipchat.com/#narrow/channel/326414-t-infra.2Fbootstrap/topic/Path.20filters.20in.20bootstrap/with/611415742) --- An awkward thing about bootstrap's Step trait is that several of its implementations represent “helper tasks” that participate in bootstrap's internal caching system, but can't be explicitly selected via command-line arguments. Those tasks need to supply dummy implementations for some Step methods related to command-line processing. This PR tries to reduce that tension by splitting the `Step` trait into two traits. --- Steps that can be selected from the command-line implement the full `CommandLineStep` trait, which also provides an implementation of `Step`. Helper tasks implement the smaller `Step` trait directly. They still participate in step-caching and step-tracing, but don't interact with command-line selectors. r? jieyouxu

…uwer Rollup of 28 pull requests Successful merges: - #159638 (bootstrap: Split the `Step` trait into multiple traits) - #159774 (rustc_trait_selection: fix trait solver hang caused by degenerate obligations) - #159837 (line-tables-only test: check that the line number matches the function name) - #159946 (Update Enzyme submodule to imporve llvm-cov) - #159962 (miri subtree update) - #156570 (tests: extend remap-path-prefix-std to all stdlib rlibs) - #159617 (Fix up `#[linkage]` target checking) - #159633 (Improve workings of attribute suggestions) - #159733 (std: Switch implementations of `thread_local!` for WASI) - #159783 (Check unsafe impls on safe EIIs) - #159810 (Add tuple never coercion collection regression test) - #159826 (Remove redundant `#[rustc_paren_sugar]` feature gate) - #159846 (Implement `str::copy_from_str`) - #159849 (rustc_parse: Stop returning `Option` from statement parsing) - #159853 (Updated expect messages for `CString` struct and method documentation) - #159875 (More cleanup in `rustc_attr_parsing`) - #159882 (Update expect messages in library/alloc/boxed.rs and library/alloc/string.rs to follow the style guide) - #159891 (Split multiline derives into std/rustc macros) - #159893 (Fix `find_attr` hygiene and `rustc_hir` cleanups) - #159895 (rustc-dev-guide subtree update) - #159902 (Clarify that the expected runtime symbols signature is for the current target only) - #159914 (Fix error in diagnostic on_unmatched_args) - #159917 (spare capacity mut constification) - #159918 (rename abort_unwind → abort_on_unwind) - #159927 (Remove sve2 from the ImpliedFeatures of AArch64 v9a.) - #159936 (Minor `rustc_ast::ast` doc cleanups) - #159945 (Update expect messages in library/core/src/ptr/non_null.rs) - #159950 (Add CFI tests for return types and never type)

JonathanBrouwer · 2026-07-26T17:09:41Z

@bors try jobs=x86_64-mingw
Running try job to debug rollup failure

rust-bors · 2026-07-26T17:09:48Z

⌛ Trying commit 7b3e992 with merge 83e6efd…

To cancel the try build, run the command @bors try cancel.

Workflow: https://github.com/rust-lang/rust/actions/runs/30211994937

bootstrap: Split the `Step` trait into multiple traits try-job: x86_64-mingw-1

rustbot added A-testsuite Area: The testsuite used to check the correctness of rustc S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-bootstrap Relevant to the bootstrap subteam: Rust's build system (x.py and src/bootstrap) labels Jul 21, 2026

rustbot assigned jieyouxu Jul 21, 2026

Zalathar mentioned this pull request Jul 21, 2026

bootstrap: Split off StepTask from the main Step trait #159423

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Kobzol reviewed Jul 21, 2026

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Comment thread src/bootstrap/src/core/builder/mod.rs

Zalathar force-pushed the step-split branch from 8d675dc to d616570 Compare July 21, 2026 07:48

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Zalathar force-pushed the step-split branch from d616570 to 1a844f2 Compare July 22, 2026 07:01

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Zalathar force-pushed the step-split branch from 1a844f2 to 9a29d54 Compare July 23, 2026 02:34

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jieyouxu approved these changes Jul 25, 2026

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Comment thread src/bootstrap/src/core/builder/cli_paths.rs Outdated

Comment thread src/bootstrap/src/core/builder/mod.rs Outdated

rustbot 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 25, 2026

Zalathar force-pushed the step-split branch from 9a29d54 to 6ac60d7 Compare July 25, 2026 14:26

Zalathar force-pushed the step-split branch from 6ac60d7 to 7b3e992 Compare July 25, 2026 14:30

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 26, 2026

jieyouxu mentioned this pull request Jul 26, 2026

Add semver check test command for checking API compatibility of stdlib #159671

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JonathanBrouwer mentioned this pull request Jul 26, 2026

Rollup of 25 pull requests #159952

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JonathanBrouwer mentioned this pull request Jul 26, 2026

Rollup of 24 pull requests #159957

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JonathanBrouwer mentioned this pull request Jul 26, 2026

Rollup of 28 pull requests #159966

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rust-bors Bot pushed a commit that referenced this pull request Jul 26, 2026

Auto merge of #159638 - Zalathar:step-split, r=<try>

83e6efd

bootstrap: Split the `Step` trait into multiple traits try-job: x86_64-mingw-1

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