T-compiler Meeting Agenda 2024-08-29

Announcements

• Next week stable Rust 1.81 is out
• Reminder: if you see a PR/issue that seems like there might be legal implications due to copyright/IP/etc, please let us know (or at least message @davidtwco or @Wesley Wiser so we can pass it along).

Other WG meetings

• None

MCPs/FCPs

• New MCPs (take a look, see if you like them!)
  • No new proposals this time.
• Old MCPs (stale MCP might be closed as per MCP procedure)
  • None at this time
• Old MCPs (not seconded, take a look)
  • “Target families for executable format” compiler-team#716 (Zulip) (last review activity: 6 months ago)
  • “Partial compilation using MIR-only rlibs” compiler-team#738 (Zulip) (last review activity: 4 months ago)
  • “Add Hotpatch flag” compiler-team#745 (Zulip) (last review activity: 3 months ago)
  • “Don’t track --emit= options as part of crate SVH” compiler-team#769 (Zulip) (last review activity: about 13 days ago)
  • “Opt-in flag for absolute paths in diagnostics” compiler-team#770 (Zulip) (last review activity: about 13 days ago)
• Pending FCP requests (check your boxes!)
  • “sanitizers: Stabilize AddressSanitizer and LeakSanitizer for the Tier 1 targets” rust#123617
  • “Add --print host-triple to print host target triple” rust#125579
• Things in FCP (make sure you’re good with it)
  • “--hint-msrv=version option so the compiler can take MSRV into account when linting” compiler-team#772 (Zulip)
  • “Don’t warn empty branches unreachable for now” rust#129103
• Accepted MCPs
  • “Enable deny(unreachable_pub) on rustc_* crates” compiler-team#773 (Zulip)
• MCPs blocked on unresolved concerns
  • “Add hygiene attributes to compile expanded source code” compiler-team#692 (Zulip) (last review activity: 7 months ago)
    • concern: added-complexity-to-frontend
  • “Add a new --build-id flag to rustc” compiler-team#635 (Zulip)
    • concern: option-name
    • concern: other-existing-options
  • “Retire the mailing list and make all decisions on zulip” compiler-team#649 (Zulip)
    • concern: automatic-sync
• Finalized FCPs (disposition merge)
  • No new finished FCP (disposition merge) this time.
• Other teams finalized FCPs
  • “stabilize const_fn_floating_point_arithmetic” rust#128596
  • “Lint at deny-by-default against references to static mut” rust#128794
  • “Non-exhaustive structs may be empty” rust#128934

WG checkins

None

Backport nominations

T-compiler beta / T-compiler stable

• :beta:“Emit specific message for time<=0.3.35” rust#129343
  • Authored by estebank
  • Discussed extensively last week, it’s a ad-hoc diag message to hint at the recent libs breakage when using (or pulling) the time crate
  • Note: this patch injects a ticking timebomb that will trigger a compile error on 1.89 when we - hopefully - assume the ecosystem has upgraded the dependency on that crate

• :beta:“Use a reduced recursion limit in the MIR inliner’s cycle breaker” rust#129714
  • Authored by saethlin
  • fixes a p-high regression from a recent crater run (though a bit flaky to reproduce)
  • as @Ben Kimock (Saethlin) points out, “this probably papers over #128887, but primarily I’m opening this PR because multiple compiler people have thought about making this change which probably means it’s a good idea.”

• No stable nominations for T-compiler this time.

T-types stable / T-types beta

• No beta nominations for T-types this time.
• No stable nominations for T-types this time.

PRs S-waiting-on-team

T-compiler

• Issues in progress or waiting on other teams

Issues of Note

Short Summary

• 1 t-compiler P-critical issues
  • 0 of those are unassigned
• 66 T-compiler P-high issues
  • 38 of those are unassigned
• 1 P-critical, 1 P-high, 3 P-medium, 0 P-low regression-from-stable-to-beta
• 0 P-critical, 0 P-high, 6 P-medium, 2 P-low regression-from-stable-to-nightly
• 0 P-critical, 36 P-high, 100 P-medium, 16 P-low regression-from-stable-to-stable

P-critical

T-compiler

• “regression: adding a def’n for node-id NodeId(597) and def kind AnonConst but a previous def’n exists” rust#128901
  • Solved by #128760 (included in #129033, merged straight in beta)

T-types

• No P-critical issues for T-types this time.

P-high regressions

P-high beta regressions

• “regression: overflow evaluating the requirement” rust#128887
  • solved by #129714 (beta backport above)

Unassigned P-high nightly regressions

• No unassigned P-high nightly regressions this time.

Performance logs

Will be posted later today

Nominated Issues

T-compiler

• “Remove HasLocalDecls.” rust#129681
  • T-compiler is called to judge if this a useful change (a counter-argument is expressed f.e. by @Michael (compiler-errors) Goulet in comment)
• “Tracking issue for release notes of #128034: exhaustiveness: Explain why a given pattern is considered unreachable” rust#129574
• “Tracking issue for release notes of #125834: treat &raw (const|mut) UNSAFE_STATIC implied deref as safe” rust#129578
  • These new tracking issues are automatically created by a new internal tool geared at improving the release notes workflow.
  • I am unsure though if the I-compiler-nominated is really useful here at this time (see @_apiraino comments here).
  • How this could work: PR author adds some verbiage for the release notes + blog post. Around release date T-* can review if the release notes of changes relevant to them are complete and clear.
  • Opinions?

RFC

• No I-compiler-nominated RFCs this time.

Oldest PRs waiting for review

T-compiler

• “Consistently use the highest bit of vector masks when converting to i1 vectors” rust#104693
  • cc: @Wesley Wiser (though not 100% sure)
• “add error message for c# style named arguments” rust#118733 (last review activity: 8 months ago)
  • 29-08-2024 cc: @Esteban Küber
• “Apply dllimport in ThinLTO for -Z dylib-lto” rust#122790
  • cc @Wesley Wiser
• “Issue 83060 fix” rust#119798 (last review activity: 4 months ago)
  • cc @Wesley Wiser

Next week’s WG checkins

None

Next meetings' agenda draft: hackmd link