Extract Rust trait methods

[ayushcodes10]

What

trait_item's branch minted the trait's own node and walked trait_bounds for supertraits, but never walked the trait's declaration_list, so a method it declared had no node at all unless some impl in the same file happened to define a same-named method, anchored at the impl's line rather than the declaration's.

Two shapes needed separate handling:

• A default-bodied trait method is a function_item, the same node type an impl method already uses, so it now routes through that existing branch via walk(member, parent_impl_nid=item_nid), mirroring what impl_item already does for its own methods.
• A signature-only method (fn foo(&self);) is a function_signature_item, a node type that had no handling anywhere in the file at all (confirmed via grep -rn "function_signature_item" returning nothing). Added a dedicated branch mirroring function_item's node/edge/parameter/return-type handling, minus the body it never has.

Verified against the reporter's exact repro

before: Greeter trait -> only .greet() (anchored at the IMPL's L14, not the declaration's L2), shout() absent entirely
after:  Greeter trait -> .greet() at L3, .shout() at L6, both anchored at the trait's own declaration

And the no-impl-anywhere case (Lonely trait, nothing implements it in the corpus): both only_signature() and with_default() now get nodes; previously zero.

sample.rs already had this exact shape (Processor.run/Logger.log, both signature-only, one with an impl in-file and one without), so added coverage there plus a dedicated fixture for the default-bodied case sample.rs doesn't otherwise exercise.

Fixes #3366.

[ayushcodes10]

@safishamsi opened this against #3366 (Rust trait method declarations produced no nodes at all, 77 percent missing across the reporter's real repos). Verified against their exact repro including the no-impl-anywhere case, plus found sample.rs already exercises the signature-only shape and added coverage there. Happy to address any feedback.

[graphify-labs]

Graphify reviewed this change.

Looks safe to merge — no coupling regressions and no blocking issues, checked against the code graph (not a self-assessment).

Formal verification. No changes could be formally verified in this run.

---

Graphify review — findings

Extracts trait method declarations in Rust, which the extractor previously skipped entirely: extract_rust now walks a trait's declaration_list, emitting a node and method edge for both bodyless function_signature_items (fn foo(&self);) and default-bodied function_items, anchored at the declaration's own line rather than at some coincidentally-matching impl. This means traits with no implementor anywhere in the corpus, and signature-only methods that had no extraction path at all, now get their methods surfaced. Adds tests covering the signature-only, no-implementor, and default-bodied cases.

No blocking issues surfaced. 2 lower-confidence candidates did not survive cross-model review.

Analysis details — impact, health, verification

Impact & health

Graphify review

Impact — 144 functions depend on the 144 functions this change touches.

Health — this change adds coupling hotspots:

• new: extract_rust() — 19 callers, 6 callees
• new: walk() — 1 callers, 8 callees

Verification — 144 functions in the blast radius were not formally verified this run (proofs are advisory here).

Gate & verification

graphify gate

PASS — objectively clean (no health regressions, tests not run — proofs not run this pass (advisory)). Grounded, not self-assessed.

Advisory (not blocking):

• verification_scope: 144 function(s) in the blast radius were not formally verified this run

Formal verification

Could not verify: Could not verify extract\_rust.

The verifier did not have enough to check extract\_rust, so it is saying so rather than guessing. No false assurance is the whole point.

Guarantee: No guarantee either way, this is an honest abstention, not a pass.

Note: Reason: parameter `path` is annotated `Path` — outside the synthesizable primitive/collection set

· 2 more finding(s) on lines outside this diff (see the check run).