build `x86_64-unknown-motor` failed

[Wyvern]

rustc 1.99.0-nightly (73dc916 2026-08-01)
target: x86_64-unknown-motor
build with -Zbuild-std

error[: mismatched types
    ╭▸ /rustc/73dc9167f1cd099e525c9ade2e068d1907b78564/library/std/src/sys/process/motor.rs:149:13
    │
149 │         let (handle, stdin, stdout, stderr) =
    │             ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ expected `SpawnResult`, found `(_, _, _, _)`
150 │             moto_rt::process::spawn(args).map_err(map_motor_error)?;
    │             ─────────────────────────────────────────────────────── this expression has type `SpawnResult`
    │
    ╰ note: expected struct `SpawnResult`
                found tuple `(_, _, _, _)`

For more information about this error, try `rustc --explain E0308`.
error: could not compile `std` (lib) due to 1 previous error

[zachs18]

Regression in de53406. Note that if it is a legacy rollup build, it might be available in rust-lang-ci@de53406.
The PR introducing the regression in this rollup is #160262 : Library lock file maintenance

searched nightlies: from nightly-2026-07-31 to nightly-2026-08-02
regressed nightly: nightly-2026-08-02
searched commit range: ad3d0bc...73dc916
regressed commit: 73dc916

bisected with cargo-bisect-rustc v0.6.11

Host triple: x86_64-unknown-linux-gnu
Reproduce with:

cargo bisect-rustc --with-src --preserve --regress error -- build -Zbuild-std=core,alloc,std,panic_abort --target x86_64-unknown-motor 

with fn main() {} in src/lib.rs

#160262 updated moto-rt from 0.16.0 to 0.16.4. In 0.16.0, moto_rt::process::spawn returns Result<(u64, RtFd, RtFd, RtFd)>, but in 0.16.4 it returns Result<SpawnResult>, where SpawnResult is a struct.

@rustbot label O-motor-os

[zachs18]

cc @lasiotus (*-unknown-motor target maintainer)

moturus/motor-os@6f1b844#diff-37762e512e788308bca5b31c747fe764f3e8f508275fe89a3e602b98cc050683

Seems like the signature change for moto_rt::process::spawn should have been a semver-major change for moto-rt?

[lasiotus]

cc @lasiotus (*-unknown-motor target maintainer)

moturus/motor-os@6f1b844#diff-37762e512e788308bca5b31c747fe764f3e8f508275fe89a3e602b98cc050683

Seems like the signature change for moto_rt::process::spawn should have been a semver-major change for moto-rt?

Ack. Sorry about that. I've yanked v0.16.4 and will publish v 0.17.0 today.

[lasiotus]

The FIX: #160392