Incremental Systems Rethought

[tomassedovic]

Metadata
Point of contact	@blyxyas
Team(s)	compiler
Goal document	2026/incremental-system-rethought

Summary

Design, propose, and implement a redesign of the incremental system to allow for shared common bases between different Rustc invocations with different arguments (i.e. cargo build and cargo check)

There's already an [on-going RFC], based on [this blog post and talk] by the same author (and this project goal's point of contact)
As my other project goals, this is a formalization of an already existing effort.

Tasks and status

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Note: we have updated the body to match the 2026 goal. Your original text is preserved below.

Details

Metadata
Point of contact	@blyxyas
Team(s)	compiler
Goal document	2026/incremental-system-rethought

Summary

Design, propose, and implement a redesign of the incremental system to allow for shared common bases between different Rustc invocations with different arguments (i.e. cargo build and cargo check)

There's already an [on-going RFC], based on [this blog post and talk] by the same author (and this project goal's point of contact)
As my other project goals, this is a formalization of an already existing effort.

Tasks and status

[tomassedovic]

This issue is intended for status updates only.

For general questions or comments, please contact the owner(s) directly.

[blyxyas]

2026-07-07 Project Update

• Partial funding has been expressed, thus starting the effort.
• We are currently in the research phase, improving documentation and refactoring the rustc_metadata and rustc_incremental modules to better allow for the big changes down the line.
• There will be a meeting between the point of contact (@blyxyas) and the compiler team champion (@jackh726) next week (2026-07-13 17:00 UTC).

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As part of those refactorings, pull requests rust-lang/rust#158859, rust-lang/rust#158695 and rust-lang/rust#158616 have been opened.

The current goal is to have some experimental experience with the incremental system, probably in the form of Build Over Check (having build not re-do check work if the conditions allow it).

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Parallel to this experimental work, the noted RFC (rust-lang/rfcs#3881) still has concerns to-be-resolved. These will be worked on at the same time.

[blyxyas]

2026-08-18 Goal Update

This update has been ready for about 10 days, just waited to publish it until we had more consolidated results.

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• A tracking issue is open, [Tracking] Incremental Systems Rethought rust#160799, with a few parallelizable issues to work on.
• On the track of parallelizing work, a few companies have offered their help in design and implementation work. Conversations are being held with these companies and it might evolve into a coordinated effort if possible.
• I've been experimenting with tracking name resolution information in this branch. This has evolved into a full fledged tool for metadata analysis (allowing for reducing information). I might publish this tool into a perm-unstable feature similar to -Zls.
• Jack Huey and I have changed the meeting schedule to biweekly.

Blockers

• None