chore(ecstore): adjudicate 32 bare dead_code allows (#6173)

Replace every bare `#[allow(dead_code)]` in ecstore with either a deletion or a per-item allow carrying a `reason`. Blanket allows at module, struct, and impl level silence the lint for future members too, so each is narrowed to the members that are actually dead.

Delete the dead cluster in `config/heal.rs` (`Config`, its three methods, `RUSTFS_BITROT_CYCLE_IN_MONTHS`, `parse_bitrot_config`) rather than annotate it: it has no callers and is unreachable outside the crate, and `parse_bitrot_config` would panic on its disabled path via `Duration::from_secs_f64(-1.0)`. `DEFAULT_KVS` stays, since the config registry uses it.

Correct two `reason` strings on `Checksum::new` and `PutObjReader::md5_current_hex_string`, which are methods but carried a field-only rationale.

Refs backlog#1823

Co-authored-by: houseme <housemecn@gmail.com>

crates/ecstore/src/bucket/bucket_target_sys.rs

@@ -1549,8 +1549,8 @@ impl Default for PutObjectOptions {
     }
 }
 
-#[allow(dead_code)]
 impl PutObjectOptions {
+    #[allow(dead_code, reason = "MinIO-parity surface with no caller in this port (backlog#1823)")]
     fn set_match_etag(&mut self, etag: &str) {
         if etag == "*" {
             self.custom_header
@@ -1561,6 +1561,7 @@ impl PutObjectOptions {
         }
     }
 
+    #[allow(dead_code, reason = "MinIO-parity surface with no caller in this port (backlog#1823)")]
     fn set_match_etag_except(&mut self, etag: &str) {
         if etag == "*" {
             self.custom_header
@@ -1696,6 +1697,7 @@ impl PutObjectOptions {
         header
     }
 
+    #[allow(dead_code, reason = "MinIO-parity surface with no caller in this port (backlog#1823)")]
     fn validate(&self, _c: Arc<TargetClient>) -> Result<(), std::io::Error> {
         //if self.checksum.is_set() {
         /*if !self.trailing_header_support {

crates/ecstore/src/bucket/lifecycle/bucket_lifecycle_ops.rs

@@ -456,16 +456,23 @@ impl<'a> LifecycleExpiryTrace<'a> {
     }
 }
 
-#[allow(dead_code)]
 impl ExpiryStats {
     pub fn missed_tasks(&self) -> i64 {
         self.missed_expiry_tasks.load(Ordering::SeqCst)
     }
 
+    #[allow(
+        dead_code,
+        reason = "asserted by this file's tests; the lib target cannot see test-only consumers (backlog#1823)"
+    )]
     fn missed_free_vers_tasks(&self) -> i64 {
         self.missed_freevers_tasks.load(Ordering::SeqCst)
     }
 
+    #[allow(
+        dead_code,
+        reason = "asserted by this file's tests; the lib target cannot see test-only consumers (backlog#1823)"
+    )]
     fn missed_tier_journal_tasks(&self) -> i64 {
         self.missed_tier_journal_tasks.load(Ordering::SeqCst)
     }

crates/ecstore/src/bucket/lifecycle/tier_last_day_stats.rs

@@ -80,7 +80,10 @@ impl LastDayTierStats {
         }
     }
 
-    #[allow(dead_code)]
+    #[allow(
+        dead_code,
+        reason = "asserted by this file's tests; the lib target cannot see test-only consumers (backlog#1823)"
+    )]
     fn merge(&self, m: LastDayTierStats) -> LastDayTierStats {
         let mut cl = self.clone();
         let mut cm = m;

crates/ecstore/src/bucket/lifecycle/tier_sweeper.rs

@@ -177,9 +177,10 @@ fn should_record_remote_delete_failure(err: &std::io::Error) -> bool {
 }
 
 #[derive(Default)]
-#[allow(dead_code)]
 struct ObjSweeper {
+    #[allow(dead_code, reason = "written but never read back (backlog#1823)")]
     object: String,
+    #[allow(dead_code, reason = "written but never read back (backlog#1823)")]
     bucket: String,
     version_id: Option<Uuid>,
     versioned: bool,
@@ -191,9 +192,9 @@ struct ObjSweeper {
     remote_object: String,
 }
 
-#[allow(dead_code)]
 impl ObjSweeper {
     #[allow(clippy::new_ret_no_self)]
+    #[allow(dead_code, reason = "MinIO-parity surface with no caller in this port (backlog#1823)")]
     pub async fn new(bucket: &str, object: &str) -> Result<Self, std::io::Error> {
         Ok(Self {
             object: object.into(),
@@ -202,17 +203,20 @@ impl ObjSweeper {
         })
     }
 
+    #[allow(dead_code, reason = "MinIO-parity surface with no caller in this port (backlog#1823)")]
     pub fn with_version(&mut self, vid: Option<Uuid>) -> &Self {
         self.version_id = vid.clone();
         self
     }
 
+    #[allow(dead_code, reason = "MinIO-parity surface with no caller in this port (backlog#1823)")]
     pub fn with_versioning(&mut self, versioned: bool, suspended: bool) -> &Self {
         self.versioned = versioned;
         self.suspended = suspended;
         self
     }
 
+    #[allow(dead_code, reason = "MinIO-parity surface with no caller in this port (backlog#1823)")]
     pub fn get_opts(&self) -> lifecycle::ObjectOpts {
         let mut opts = ObjectOpts {
             version_id: self.version_id.clone(),
@@ -226,6 +230,7 @@ impl ObjSweeper {
         opts
     }
 
+    #[allow(dead_code, reason = "MinIO-parity surface with no caller in this port (backlog#1823)")]
     pub fn set_transition_state(&mut self, info: TransitionedObject) {
         self.transition_tier = info.tier;
         self.transition_status = info.status;
@@ -266,6 +271,7 @@ impl ObjSweeper {
         None
     }
 
+    #[allow(dead_code, reason = "MinIO-parity surface with no caller in this port (backlog#1823)")]
     pub async fn sweep(&self, api: Arc<ECStore>) {
         let Some(je) = self.should_remove_remote_object() else {
             return;

crates/ecstore/src/bucket/quota/mod.rs

@@ -312,9 +312,7 @@ mod tests {
         }
         #[derive(Deserialize)]
         struct LegacyBucketQuota {
-            #[allow(dead_code)]
             quota: Option<u64>,
-            #[allow(dead_code)]
             quota_type: LegacyQuotaType,
         }
         let legacy = serde_json::from_slice::<LegacyBucketQuota>(&json)