fix: bump the nightly past a codegen ICE that broke the Linux release build

[andrewgazelka]

nix build .#packages.x86_64-linux.bedwars died in the compiler:

error: internal compiler error: compiler/rustc_codegen_ssa/src/mir/operand.rs:291:18:
  not immediate: OperandRef(Uninit @ TyAndLayout {
    ty: unsafe_cell::UnsafeCell<MaybeUninit<runtime::task::Notified<Arc<multi_thread::handle::Handle>>>>,
    ... backend_repr: Scalar(union pointer) ... })

What the differentials said

The upstream issue carries an 8-line reproduction, which turns a 40-minute nix build into a sub-second rustc call, so all of these ran against that rather than the workspace.

• Optimisation level. ICEs at 2 and 3, clean at 0 and 1. So Tests (ubuntu-latest) being green proves nothing: it is a debug build and cargoUnit compiles at -C opt-level=3.
• Architecture. Not x86. It ICEs identically on aarch64-apple-darwin, same assertion, same line. The bug is in target-independent codegen_return_terminator.
• Nightly. Clean on 07-23, ICE on 07-24 through 07-26, clean again on 07-27.
• A newer tokio. Does not exist. 1.53.1 is the newest published.

The fix

Bump the pin forward one day, to the nightly that carries rust-lang/rust#159825, which fixes #159815. Root cause upstream: #157797 added OperandValue::Uninit and missed the PassMode::Direct | PassMode::Pair branch.

Forward rather than back, deliberately. Rolling back to 07-23 also works, but it is a knob someone has to remember to remove and it strands the workspace three days behind. Bumping forward becomes an ordinary pin the moment the fix reaches beta.

Rejected: opt-level=1 for tokio only, which permanently deoptimises the async runtime of a game server to work around a compiler bug that is already fixed.

Verified

The whole workspace moves with a toolchain pin, so every gate was re-run.

cargo check --workspace --all-targets   rc=0
nix run .#lint                          rc=0
nix run .#test                          rc=0   447 passed, 1 skipped
nix run .#e2e -- --seconds 12           rc=0   3729 LevelChunkWithLight
nix build x86_64-linux bedwars + proxy  rc=0

/nix/store/rabbfr795mbs20n0qwdmjvlfa3ibprv3-bedwars-0.1.0
/nix/store/qp3ykmwsy35df2hrblaaz77frs6xbjyb-hyperion-proxy-0.1.0

Zero occurrences of internal compiler error in the full build log.

(sent by an AI agent via Claude Code, model claude-opus-4-6)

[github-actions]

Benchmark Results for general

ray_intersection/aabb_size_0.1                     [  17.3 ns ...  17.2 ns ]      -0.72%*
ray_intersection/aabb_size_1                       [  17.3 ns ...  17.1 ns ]      -1.01%*
ray_intersection/aabb_size_10                      [  17.3 ns ...  17.2 ns ]      -0.57%*
ray_intersection/ray_distance_1                    [   1.5 ns ...   1.5 ns ]      +0.13%
ray_intersection/ray_distance_5                    [   1.5 ns ...   1.5 ns ]      -0.06%
ray_intersection/ray_distance_20                   [   1.5 ns ...   1.5 ns ]      -0.26%
overlap/no_overlap                                 [  15.9 ns ...  15.9 ns ]      +0.36%
overlap/partial_overlap                            [  15.9 ns ...  15.9 ns ]      -0.04%
overlap/full_containment                           [  14.9 ns ...  14.9 ns ]      +0.03%
point_containment/inside                           [   6.0 ns ...   6.0 ns ]      +0.19%
point_containment/outside                          [   6.0 ns ...   6.1 ns ]      +0.62%
point_containment/boundary                         [   6.1 ns ...   6.1 ns ]      -0.19%

Comparing to 8d9680c

[github-actions]

Benchmark Results for general

ray_intersection/aabb_size_0.1                     [  18.8 ns ...  18.8 ns ]      -0.32%
ray_intersection/aabb_size_1                       [  18.7 ns ...  18.8 ns ]      +0.09%
ray_intersection/aabb_size_10                      [  18.8 ns ...  18.8 ns ]      -0.03%
ray_intersection/ray_distance_1                    [   1.3 ns ...   1.3 ns ]      -0.32%
ray_intersection/ray_distance_5                    [   1.3 ns ...   1.3 ns ]      -0.04%
ray_intersection/ray_distance_20                   [   1.3 ns ...   1.3 ns ]      -0.13%
overlap/no_overlap                                 [  15.9 ns ...  15.8 ns ]      -1.02%*
overlap/partial_overlap                            [  16.2 ns ...  16.0 ns ]      -1.09%*
overlap/full_containment                           [  14.4 ns ...  14.5 ns ]      +0.48%
point_containment/inside                           [   5.7 ns ...   5.4 ns ]      -5.42%*
point_containment/outside                          [   5.4 ns ...   5.7 ns ]      +5.84%*
point_containment/boundary                         [   5.4 ns ...   5.4 ns ]      +0.36%

Comparing to d8cd11d

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 40.91%. Comparing base (8d9680c) to head (9990b05).
⚠️ Report is 1 commits behind head on main.

@@            Coverage Diff             @@
##             main     #984      +/-   ##
==========================================
- Coverage   41.01%   40.91%   -0.11%     
==========================================
  Files         226      239      +13     
  Lines       24181    25697    +1516     
  Branches      957     1004      +47     
==========================================
+ Hits         9917    10513     +596     
- Misses      14049    14966     +917     
- Partials      215      218       +3     

see 4 files with indirect coverage changes

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