refactor(test): inline the uninstall GC cleanup check

Inline the single-use ensure_empty helper and replace GcErr with an inline error. Preserve the existing directory and GC filename filter.

Author: Cloud0310

tests/suite/cli_self_upd.rs

@@ -395,39 +395,31 @@ async fn uninstall_doesnt_leave_gc_file() {
     // 100ms, but during the contention of test suites can be substantially
     // longer while still succeeding.
 
-    let check = || ensure_empty(parent);
+    let check = || {
+        let garbage = fs::read_dir(parent)
+            .unwrap()
+            .filter_map(|entry| {
+                let path = entry.unwrap().path();
+                let name = path.file_name()?.to_str()?;
+                // On Windows, this binary is cleaned up on exit
+                if !(name.starts_with("rustup-gc-") && name.ends_with(EXE_SUFFIX)) {
+                    return None;
+                }
+                Some(path.to_string_lossy().to_string())
+            })
+            .collect::<Vec<_>>();
+        if garbage.is_empty() {
+            Ok(())
+        } else {
+            Err(format!("garbage remaining: {garbage:?}"))
+        }
+    };
     match retry(Fibonacci::from_millis(1).map(jitter).take(23), check) {
         Ok(_) => (),
         Err(e) => panic!("{e}"),
     }
 }
 
-#[cfg(windows)]
-fn ensure_empty(dir: &Path) -> Result<(), GcErr> {
-    let garbage = fs::read_dir(dir)
-        .unwrap()
-        .filter_map(|entry| {
-            let path = entry.unwrap().path();
-            let name = path.file_name()?.to_str()?;
-            // On Windows, this binary is cleaned up on exit
-            if !(name.starts_with("rustup-gc-") && name.ends_with(EXE_SUFFIX)) {
-                return None;
-            }
-            Some(path.to_string_lossy().to_string())
-        })
-        .collect::<Vec<_>>();
-    if garbage.is_empty() {
-        Ok(())
-    } else {
-        Err(GcErr(garbage))
-    }
-}
-
-#[derive(thiserror::Error, Debug)]
-#[error("garbage remaining: {:?}", .0)]
-#[cfg(windows)]
-struct GcErr(Vec<String>);
-
 #[tokio::test]
 async fn update_exact() {
     let cx = SelfUpdateTestContext::new(TEST_VERSION).await;