add test for bug #15703

Author: hkBst

src/cargo/util/toml/targets.rs

@@ -752,7 +752,7 @@ fn infer_any(package_root: &Path, entry: &DirEntry) -> Option<(String, PathBuf)>
 
 fn infer_file(package_root: &Path, entry: &DirEntry) -> Option<(String, PathBuf)> {
     let path = entry.path();
-    let stem = path.file_stem()?.to_str()?.to_owned();
+    let stem = path.file_name()?.to_str()?.to_owned();
     let path = path
         .strip_prefix(package_root)
         .map(|p| p.to_owned())

tests/testsuite/bench.rs

@@ -3,6 +3,36 @@
 use crate::prelude::*;
 use cargo_test_support::{basic_bin_manifest, basic_lib_manifest, basic_manifest, project, str};
 
+#[cargo_test]
+fn cargo_bench_find_benches() {
+    let manifest = r#"
+        [package]
+        name = "find-benches"
+        edition = "2024"
+
+        [[bench]]
+        name = "benches.rs"
+        "#;
+
+    let p = project()
+        .file("Cargo.toml", &manifest)
+        .file("src/lib.rs", "")
+        .file("benches/benches.rs", "")
+        .build();
+
+    let stderr_data = str![[r#"
+[ERROR] failed to parse manifest at `[ROOT]/foo/Cargo.toml`
+
+Caused by:
+  can't find `benches.rs` bench at `benches/benches.rs.rs` or `benches/benches.rs/main.rs`. Please specify bench.path if you want to use a non-default path.
+
+"#]];
+    p.cargo("bench")
+        .with_status(101)
+        .with_stderr_data(stderr_data)
+        .run();
+}
+
 #[cargo_test(nightly, reason = "bench")]
 fn cargo_bench_simple() {
     let p = project()