`cargo rustc` panics on unknown bin

[jyn514]

Problem

thread 'main' panicked at src/tools/cargo/src/cargo/ops/cargo_compile/unit_generator.rs:302:26:
The number of packages must be at least 1
stack backtrace:
   3: core::option::expect_failed
             at /rustc/13e87909494f2f31bce51bc106e2b629420d1235/library/core/src/option.rs:2049:5
   4: <cargo::ops::cargo_compile::unit_generator::UnitGenerator>::list_rule_targets
   5: <cargo::ops::cargo_compile::unit_generator::UnitGenerator>::generate_root_units
   6: cargo::ops::cargo_compile::create_bcx
   7: cargo::ops::cargo_compile::compile_ws
   8: cargo::ops::cargo_compile::compile_with_exec
   9: cargo::ops::cargo_compile::compile
  10: cargo::commands::rustc::exec
  11: <cargo::cli::Exec>::exec
  12: cargo::main

Steps

1. cargo new cargo-bug
2. cd cargo-bug
3. mkdir src/bin
4. cargo rustc --bin main

Possible Solution(s)

No response

Notes

No response

Version

cargo 1.88.0-nightly (7918c7eb5 2025-04-27)
release: 1.88.0-nightly
commit-hash: 7918c7eb59614c39f1c4e27e99d557720976bdd7
commit-date: 2025-04-27
host: x86_64-unknown-linux-gnu
libgit2: 1.9.0 (sys:0.20.0 vendored)
libcurl: 8.12.1-DEV (sys:0.4.80+curl-8.12.1 vendored ssl:OpenSSL/3.4.1)
ssl: OpenSSL 3.4.1 11 Feb 2025
os: Pop!_OS 22.4.0 (jammy) [64-bit]

[epage]

Step (3) is not needed. Whats important is specifying an invalid --bin. Passing in --bin cargo-bug works.

Confirmed that

• this is happens on nightly and beta but not stable
• this only happens for rustc and not check or build

[epage]

I think I've narrowed this down to #15199, specifically fa7712d

... that would have gone faster looking at the backtrace