[BUG][auto] rust/rust-unimported-bare-name-resolved-tree-wide: a Send bound is counted as a dependency on the crate's own struct Send in an unrelated private module #215

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1. DaisukeYoda

   added

   bugSomething isn't workingSomething isn't working

   P2Medium priorityMedium priority

   auto-filedFiled automatically by the polyscan-fp-audit skill (review before acting)Filed automatically by the polyscan-fp-audit skill (review before acting)

   on Oct 31, 2026
2. DaisukeYoda commented on Oct 31, 2026

   

   DaisukeYoda

   on Oct 31, 2026

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   The same fallback also fires on two other kinds of bare name, found by the triage pass on cfal/shoes with an instrumented build:

   • The name of an associated type item is captured as a reference: type Send = UdpSender; and type Recv = UdpReceiver; at src/wireguard/io.rs:133-134 resolve to src/xhttp/h3.rs:152 and :157, type Value = ConfigSelection<T> at src/config/types/selection.rs:98 resolves to rule_set/geodata.rs:30, and type Udp = ... at src/dns/proxy_runtime.rs:82 resolves to wireguard/io.rs:79.
   • A file-local type alias is never registered as a local name, so a use of it falls through to the tree: type Connection (src/dns/exchange.rs:18, used at :27) resolves to xhttp/h3.rs:12, and type Reservation (src/xhttp/stream.rs:630, used at :626) resolves to xhttp/carrier.rs:26.

   Gating the tree-wide lookup on a glob import covers all three cases.
3. DaisukeYoda commented on Nov 7, 2026

   

   DaisukeYoda

   on Nov 7, 2026

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   Associated-type labels are still counted when the tree declares a type of the same name in the same file. A glob gate on the tree-wide lookup does not reach that case, because the name resolves locally before the lookup runs.

   // src/lib.rs
   pub struct Item {
       pub id: u32,
   }
   
   pub struct Numbers {
       values: Vec<u8>,
   }
   
   impl Numbers {
       pub fn iter(&self) -> impl Iterator<Item = &u8> {
           self.values.iter()
       }
   }
   
   pub struct Counter {
       n: u8,
   }
   
   impl Iterator for Counter {
       type Item = u8;
       fn next(&mut self) -> Option<Self::Item> {
           self.n += 1;
           Some(self.n)
       }
   }

   polyscan analyze --format json --select cbo . prints:

   {"name":"Numbers","coupling_count":1,"dependent_classes":["Item"]}
   {"name":"Counter","coupling_count":1,"dependent_classes":["Item"]}

   Neither type refers to struct Item. Item is the label of Iterator<Item = ..> and of type Item = u8;. A label such as Item, Target, Output or Error is not a type reference wherever the same-named type is declared.

   The tree-wide case is widespread on EmbarkStudios/quilkin@58f4f0b: 54 of its 515 listed Rust types carry a dependency that comes only from such a label. Item (a private struct in src/net/io/nic/xdp/process.rs:307) is counted for 28 types through impl Iterator<Item = ..>. Target (a private enum in crates/test/src/bin/loadtest/main.rs:136) is counted for 10 types whose only use is impl Deref { type Target = ..; }. Configuration (pub trait Configuration in crates/xds/src/config.rs:236) is counted for 15 filters and the StaticFilter trait, through type Configuration = Config;. Six types drop from high to medium once these entries are removed: Pass, Capture, Debug, Drop, Match and HashedTokenRouter. Pass (src/filters/pass.rs:24) is a unit struct with no-op read/write methods, and it is reported at CBO 8, high.

   polyscan version 0.6.1. Found via the polyscan-enhancement-audit skill.