From 02ec8d48e53fef1c14ff271203ba5c661b6b2a01 Mon Sep 17 00:00:00 2001
From: Ed Page <eopage@gmail.com>
Date: Tue, 6 May 2025 11:05:10 -0500
Subject: [PATCH 1/3] test(rustc): Show the bug

---
 tests/testsuite/rustc.rs | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/tests/testsuite/rustc.rs b/tests/testsuite/rustc.rs
index 6e9b5b228..8c17fd2bc 100644
--- a/tests/testsuite/rustc.rs
+++ b/tests/testsuite/rustc.rs
@@ -533,6 +533,29 @@ fn fail_with_multiple_packages() {
         .run();
 }
 
+#[cargo_test]
+fn fail_with_bad_bin_no_package() {
+    let p = project()
+        .file(
+            "src/main.rs",
+            r#"
+                fn main() { println!("hello a.rs"); }
+            "#,
+        )
+        .build();
+
+    p.cargo("rustc --bin main")
+        .with_status(101)
+        .with_stderr_data(str![[r#"
+
+thread 'main' panicked [..]:
+The number of packages must be at least 1
+...
+
+"#]])
+        .run();
+}
+
 #[cargo_test]
 fn fail_with_glob() {
     let p = project()

From 981ea84bdc9fb095e818b65c70bca27d7504c82b Mon Sep 17 00:00:00 2001
From: Ed Page <eopage@gmail.com>
Date: Tue, 6 May 2025 11:10:12 -0500
Subject: [PATCH 2/3] refactor(compile): Make unmatched_packages optional

---
 src/cargo/ops/cargo_compile/unit_generator.rs | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/cargo/ops/cargo_compile/unit_generator.rs b/src/cargo/ops/cargo_compile/unit_generator.rs
index 588581457..c11406bc4 100644
--- a/src/cargo/ops/cargo_compile/unit_generator.rs
+++ b/src/cargo/ops/cargo_compile/unit_generator.rs
@@ -294,16 +294,16 @@ impl<'a> UnitGenerator<'a, '_> {
 
             let unmatched_packages = match self.spec {
                 Packages::Default | Packages::OptOut(_) | Packages::All(_) => {
-                    "default-run packages".to_owned()
+                    " in default-run packages".to_owned()
                 }
                 Packages::Packages(packages) => {
                     let first = packages
                         .first()
                         .expect("The number of packages must be at least 1");
                     if packages.len() == 1 {
-                        format!("`{}` package", first)
+                        format!(" in `{}` package", first)
                     } else {
-                        format!("`{}`, ... packages", first)
+                        format!(" in `{}`, ... packages", first)
                     }
                 }
             };
@@ -313,7 +313,7 @@ impl<'a> UnitGenerator<'a, '_> {
             let mut msg = String::new();
             write!(
                 msg,
-                "no {target_desc} target {named} `{target_name}` in {unmatched_packages}{suggestion}",
+                "no {target_desc} target {named} `{target_name}`{unmatched_packages}{suggestion}",
             )?;
             if !targets_elsewhere.is_empty() {
                 append_targets_elsewhere(&mut msg)?;

From f83e11acfed3f71e3c9657e3dd3f2f8196e173b2 Mon Sep 17 00:00:00 2001
From: Ed Page <eopage@gmail.com>
Date: Tue, 6 May 2025 11:13:30 -0500
Subject: [PATCH 3/3] fix(rustc): Don't panic on unknown bins

This takes the most surgical, direct route to addressing the problem.
Alternatively, we could look into why `cargo rustc` and `cargo check`
are different.

Fixes #15493
---
 src/cargo/ops/cargo_compile/unit_generator.rs | 15 +++++----------
 tests/testsuite/rustc.rs                      |  6 +++---
 2 files changed, 8 insertions(+), 13 deletions(-)

diff --git a/src/cargo/ops/cargo_compile/unit_generator.rs b/src/cargo/ops/cargo_compile/unit_generator.rs
index c11406bc4..3c984f476 100644
--- a/src/cargo/ops/cargo_compile/unit_generator.rs
+++ b/src/cargo/ops/cargo_compile/unit_generator.rs
@@ -296,16 +296,11 @@ impl<'a> UnitGenerator<'a, '_> {
                 Packages::Default | Packages::OptOut(_) | Packages::All(_) => {
                     " in default-run packages".to_owned()
                 }
-                Packages::Packages(packages) => {
-                    let first = packages
-                        .first()
-                        .expect("The number of packages must be at least 1");
-                    if packages.len() == 1 {
-                        format!(" in `{}` package", first)
-                    } else {
-                        format!(" in `{}`, ... packages", first)
-                    }
-                }
+                Packages::Packages(packages) => match packages.len() {
+                    0 => String::new(),
+                    1 => format!(" in `{}` package", packages[0]),
+                    _ => format!(" in `{}`, ... packages", packages[0]),
+                },
             };
 
             let named = if is_glob { "matches pattern" } else { "named" };
diff --git a/tests/testsuite/rustc.rs b/tests/testsuite/rustc.rs
index 8c17fd2bc..da32f20ac 100644
--- a/tests/testsuite/rustc.rs
+++ b/tests/testsuite/rustc.rs
@@ -547,9 +547,9 @@ fn fail_with_bad_bin_no_package() {
     p.cargo("rustc --bin main")
         .with_status(101)
         .with_stderr_data(str![[r#"
-
-thread 'main' panicked [..]:
-The number of packages must be at least 1
+[ERROR] no bin target named `main`
+[HELP] available bin targets:
+    foo
 ...
 
 "#]])