fix(rust): qualify generic/lifetime impl methods by the implementing type, not the trait (#1588)

`impl<T> Source for BufSource<T>` recorded its `read` as `Source::read`: the
receiver rule took the LAST bare `type_identifier` child of the impl_item,
and once the implementing type carries parameters it parses as a
`generic_type`, leaving the trait's identifier as the only bare one. The
method was then unaddressable by its type, collided with the trait's own
declaration, and — carrying the trait's name — the interface-impl
synthesizer treated the impl body as a second declaration and fanned out
dispatch edges from it (a body like `{ 0 }` with no call at all). A lifetime
alone triggered it (`impl<'a> Iterator for Parents<'a>`), as did a reference
implementing type (`impl Trait for &Foo`).

Both extractors now read the grammar's named fields: the implementing type
from `impl_item.type` (generic_type → its bare name, scoped → last segment,
reference → the inner type; tuple / dyn / pointer / primitive → no receiver,
exactly as before) and the trait from `impl_item.trait`. The native kernel
mirrored the old rule bug-for-bug for parity; it changes in lockstep here, so
the parity fixture grows the generic / lifetime / reference / scoped /
generic-trait impl shapes and the design notes drop the "preserve" marker.

ripgrep (110 files): nodes 4029 → 4029; trait-mis-qualified impl methods
61 → 0; synthesized dispatch edges originating outside any trait declaration
38 → 0 while genuine ones rose 33 → 52; plain calls edges unchanged (9098).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LxZj6W6Y1SHXwvpT3uwJpK

CHANGELOG.md

@@ -71,6 +71,7 @@ and adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 - Files skipped because they are too large or repeatedly fail to parse are now recorded with the reason, so unchanged rejected files are no longer rediscovered and retried on every status check and sync — and a later successful parse of such a file replaces the record with its real symbols. Thanks @netbrah for the exceptional failure analysis behind this batch, and @danusha2345 for the fixes. (#1557)
 - C/C++ function-pointer analysis now bounds its compiled-pattern caches, so very large repositories can no longer exhaust the JavaScript engine's regular-expression code space during indexing. (#1559)
 - JSX rendering analysis now runs only on JavaScript-family files, so JSX-looking strings in C/C++ (or any other language) no longer create impossible call edges — in pure-C projects and in mixed-language monorepos alike. (#1560)
+- Methods implemented in a generic or lifetime-parameterized `impl` block (`impl<T> Source for BufSource<T>`, `impl<'a> Iterator for Parents<'a>`) are now recorded under the implementing type instead of the trait. Previously such a method could not be found by its type — "who calls `BufSource::read`" had no answer — and it collided with the trait's own declaration, which could even invent a call-graph edge out of an impl body that contains no call at all. Impls on a reference (`impl Trait for &Foo`) and on a module-qualified type (`impl Trait for m::Foo`) are attributed to their type too. Re-index after upgrading. Thanks @Dshuishui. (#1588) (Rust)
 
 ## [1.5.0] - 2026-07-21
 

__tests__/extraction.test.ts

@@ -1131,6 +1131,111 @@ impl Cache for MyCache {
     expect(implRef?.fromNodeId).toBe(myCacheNode?.id);
   });
 
+  it('qualifies methods of a generic or lifetime impl by the implementing type, not the trait (#1588)', () => {
+    const code = `
+pub trait Source {
+    fn read(&mut self) -> usize;
+}
+
+pub struct FileSource { pub n: usize }
+impl Source for FileSource {
+    fn read(&mut self) -> usize { self.n }
+}
+
+pub struct BufSource<T> { pub inner: T }
+impl<T> Source for BufSource<T> {
+    fn read(&mut self) -> usize { 0 }
+}
+
+pub struct Parents<'a> { cur: &'a u32 }
+impl<'a> Iterator for Parents<'a> {
+    type Item = u32;
+    fn next(&mut self) -> Option<u32> { None }
+}
+
+pub struct Wrapper { pub n: usize }
+impl Source for &Wrapper {
+    fn read(&mut self) -> usize { 1 }
+}
+
+pub mod m { pub struct Scoped { pub n: usize } }
+impl Source for m::Scoped {
+    fn read(&mut self) -> usize { 2 }
+}
+
+pub struct Own { pub n: usize }
+impl From<u32> for Own {
+    fn from(n: u32) -> Self { Own { n: n as usize } }
+}
+`;
+    const result = extractFromSource('src.rs', code);
+
+    // Every impl method is qualified by the IMPLEMENTING type. Before, a
+    // parameterized implementing type (`BufSource<T>`, `Parents<'a>`, `&Wrapper`)
+    // left the trait's identifier as the only bare type_identifier child of the
+    // impl, so those methods were recorded as `Source::read` / `Iterator::next`.
+    const methodQns = result.nodes
+      .filter((n) => n.kind === 'method')
+      .map((n) => n.qualifiedName)
+      .sort();
+    expect(methodQns).toEqual([
+      'BufSource::read',
+      'FileSource::read',
+      'Own::from',
+      'Parents::next',
+      'Scoped::read',
+      'Source::read',
+      'Wrapper::read',
+    ]);
+    // The trait's qualified name now names exactly one node: its declaration.
+    const traitRead = result.nodes.filter((n) => n.qualifiedName === 'Source::read');
+    expect(traitRead).toHaveLength(1);
+    expect(traitRead[0]!.startLine).toBe(3);
+
+    // The implements back-reference comes FROM the implementing type's node
+    // for every impl shape, named by the trait's full text.
+    const implementsFrom = (typeName: string): string[] => {
+      const typeNode = result.nodes.find((n) => n.name === typeName && n.kind === 'struct');
+      expect(typeNode, typeName).toBeDefined();
+      return result.unresolvedReferences
+        .filter((r) => r.referenceKind === 'implements' && r.fromNodeId === typeNode!.id)
+        .map((r) => r.referenceName);
+    };
+    expect(implementsFrom('FileSource')).toEqual(['Source']);
+    expect(implementsFrom('BufSource')).toEqual(['Source']);
+    expect(implementsFrom('Parents')).toEqual(['Iterator']);
+    expect(implementsFrom('Wrapper')).toEqual(['Source']);
+    expect(implementsFrom('Scoped')).toEqual(['Source']);
+    expect(implementsFrom('Own')).toEqual(['From<u32>']);
+
+    // …and the owner `contains` edge lands on the implementing type too.
+    const buf = result.nodes.find((n) => n.name === 'BufSource' && n.kind === 'struct')!;
+    const bufRead = result.nodes.find((n) => n.qualifiedName === 'BufSource::read')!;
+    expect(
+      result.edges.some((e) => e.kind === 'contains' && e.source === buf.id && e.target === bufRead.id)
+    ).toBe(true);
+  });
+
+  it('gives no receiver to an impl whose target names no single type', () => {
+    // A tuple / `dyn Trait` / primitive implementing type has no struct to
+    // hang the methods off, so they are extracted as plain functions — the
+    // pre-#1588 behavior for these shapes, minus the trait mis-qualification.
+    const code = `
+pub trait Base { fn id(&self) -> u32; }
+impl Base for (u32, u32) {
+    fn id(&self) -> u32 { 0 }
+}
+impl Base for dyn Base {
+    fn id(&self) -> u32 { 1 }
+}
+`;
+    const result = extractFromSource('src.rs', code);
+    const ids = result.nodes.filter((n) => n.name === 'id');
+    expect(ids.map((n) => n.qualifiedName).sort()).toEqual(['Base::id', 'id', 'id']);
+    expect(ids.filter((n) => n.kind === 'function')).toHaveLength(2);
+    expect(result.unresolvedReferences.filter((r) => r.referenceKind === 'implements')).toHaveLength(0);
+  });
+
   it('should extract trait supertraits as extends references', () => {
     const code = `
 pub trait Display {}

__tests__/fixtures/kernel-parity/torture.rs

@@ -107,6 +107,71 @@ impl Render for Container<u32> {
     fn render(&self) {}
 }
 
+/// Receiver = the impl_item's `type` field (#1588): generic, lifetime,
+/// reference, scoped, and generic-trait impls all qualify by the TYPE.
+pub trait Source {
+    fn read(&mut self) -> usize;
+}
+
+pub struct FileSource {
+    pub n: usize,
+}
+
+impl Source for FileSource {
+    fn read(&mut self) -> usize {
+        self.n
+    }
+}
+
+pub struct BufSource<T> {
+    pub inner: T,
+}
+
+impl<T> Source for BufSource<T> {
+    fn read(&mut self) -> usize {
+        0
+    }
+}
+
+pub struct Parents<'a> {
+    cur: &'a u32,
+}
+
+impl<'a> Iterator for Parents<'a> {
+    type Item = u32;
+    fn next(&mut self) -> Option<u32> {
+        None
+    }
+}
+
+impl<T: Clone> Container<T> {
+    fn dup(&self) -> T {
+        self.item.clone()
+    }
+}
+
+impl Base for &Widget {}
+
+impl<T> Render for &mut BufSource<T> {
+    fn render(&self) {}
+}
+
+impl Base for self::Deep {}
+
+impl From<u32> for FileSource {
+    fn from(n: u32) -> Self {
+        FileSource { n: n as usize }
+    }
+}
+
+impl Base for (u32, u32) {}
+
+impl Render for dyn Base {
+    fn render(&self) {}
+}
+
+impl Base for u32 {}
+
 impl Later {
     fn touch(&self) {}
 }

__tests__/kernel-rustlang-parity.test.ts

@@ -4,8 +4,8 @@
  * Asserts the native walker (codegraph-kernel/src/rustlang.rs) produces the
  * SAME ExtractionResult as the wasm TreeSitterExtractor — nodes, edges, and
  * unresolved refs compared as canonicalized multisets — over the checked-in
- * torture fixture (torture.rs: impl/trait quirks incl. the
- * `impl Trait for Generic<T>` trait-receiver bug, unit-struct skip, phantom
+ * torture fixture (torture.rs: impl/trait quirks incl. generic / lifetime /
+ * reference / scoped / generic-trait impl receivers (#1588), unit-struct skip, phantom
  * const identifiers, use-binding refs incl. nested groups + wildcard-emits-
  * nothing, chained-call re-encode, turbofish, Rocket route macros body-only,
  * fn-ref shapes, value-ref shadowing, attribute-broken docstrings, dead-code

__tests__/resolution.test.ts

@@ -1119,6 +1119,59 @@ impl Describe for Ctl { fn describe(&self) -> String { "ctl".into() } }
       ).toBe('interface-impl');
     });
 
+    it('qualifies a generic impl by its type, so trait dispatch reaches it and no edge is invented from its body (#1588)', async () => {
+      // `impl<T> Source for BufSource<T>`: the implementing type parses as a
+      // generic_type, so the old positional receiver scan picked the TRAIT.
+      // The impl's `read` was recorded as `Source::read` — unaddressable as
+      // `BufSource::read` — and, carrying the trait's name, the interface-impl
+      // synthesizer treated its body (`{ 0 }`, no call at all) as a second
+      // declaration and gave it a dispatch edge to FileSource's implementation.
+      fs.writeFileSync(
+        path.join(tempDir, 'lib.rs'),
+        `pub trait Source {
+    fn read(&mut self) -> usize;
+}
+
+pub struct FileSource { pub n: usize }
+impl Source for FileSource {
+    fn read(&mut self) -> usize { self.n }
+}
+
+pub struct BufSource<T> { pub inner: T }
+impl<T> Source for BufSource<T> {
+    fn read(&mut self) -> usize { 0 }
+}
+`
+      );
+
+      cg = await CodeGraph.init(tempDir, { index: true });
+
+      const methods = cg.getNodesByKind('method');
+      const traitDecls = methods.filter((n) => n.qualifiedName === 'Source::read');
+      expect(traitDecls, 'only the declaration carries the trait-qualified name').toHaveLength(1);
+      const traitMethod = traitDecls[0]!;
+      expect(traitMethod.startLine).toBe(2);
+      const fileImpl = methods.find((n) => n.qualifiedName === 'FileSource::read');
+      const bufImpl = methods.find((n) => n.qualifiedName === 'BufSource::read');
+      expect(fileImpl).toBeDefined();
+      expect(bufImpl, 'the generic impl is addressable by its type').toBeDefined();
+
+      const synth = (id: string) =>
+        cg.getOutgoingEdges(id).filter((e) => e.kind === 'calls' && e.provenance === 'heuristic');
+      // Dispatch fans out from the declaration to BOTH implementations…
+      const fromTrait = synth(traitMethod.id);
+      expect(new Set(fromTrait.map((e) => e.target))).toEqual(new Set([fileImpl!.id, bufImpl!.id]));
+      for (const e of fromTrait) {
+        expect(
+          (e.metadata as { synthesizedBy?: string } | undefined)?.synthesizedBy
+        ).toBe('interface-impl');
+        expect(e.line, 'registered at the declaration, never at an impl body').toBe(2);
+      }
+      // …and neither implementation body sprouts a synthesized call of its own.
+      expect(synth(fileImpl!.id)).toHaveLength(0);
+      expect(synth(bufImpl!.id)).toHaveLength(0);
+    });
+
     it('records instantiates for C++ stack/brace construction, targeting the class (#1035)', async () => {
       // `Calculator calc(0)` (direct-init) and `Widget w{1, 2}` (brace-init)
       // carry the constructor args directly on the declarator — there's no

codegraph-kernel/src/rustlang.rs

@@ -11,10 +11,11 @@
 //! - impl blocks push NO scope: members re-dispatch at file scope, so an impl
 //!   associated `const` becomes a FILE-level `variable`, and the method↔owner
 //!   `contains` edge is a source-order name scan (an impl ABOVE its struct
-//!   gets no edge). `impl Trait for Generic<T>`'s receiver resolves to the
-//!   TRAIT (the only direct type_identifier), and methods get QN
-//!   `Trait::method` — preserve, never "fix" via the grammar's trait:/type:
-//!   fields.
+//!   gets no edge). The receiver (method QN prefix, `contains` owner,
+//!   `implements` source) is the impl_item's `type` field via
+//!   impl_type_name — both sides moved to the grammar's trait:/type: fields
+//!   together in #1588 (the earlier positional scan qualified every
+//!   parameterized impl's methods by the TRAIT).
 //! - `const_item`/`static_item` ride the generic extractVariable fallback:
 //!   kind is always `variable`, no signature, and EVERY direct `identifier`
 //!   child mints a node (`const MAX: u32 = OTHER;` → two nodes, `MAX` + the
@@ -399,33 +400,35 @@ impl<'t> Walker<'t> {
         Some(if last == "Self" { "self".to_string() } else { last.to_string() })
     }
 
-    /// rustExtractor.getReceiverType: parent-walk to the nearest impl_item;
-    /// LAST direct type_identifier child wins (for `impl Trait for Generic<T>`
-    /// that's the TRAIT — bug preserved); else the first generic_type's inner
-    /// type_identifier.
+    /// rustImplTypeName (languages/rust.ts) — the implementing type's simple
+    /// name for an impl block, from the grammar's `type` field (#1588):
+    /// `impl<T> Tr for G<T>` / `impl<'a> Iterator for Parents<'a>` /
+    /// `impl Tr for &Foo` / `impl Tr for m::Foo` → `G` / `Parents` / `Foo` /
+    /// `Foo`. Shapes naming no single type (tuple, `dyn Tr`, pointer,
+    /// primitive, fn type…) → None. Mirrored byte-for-byte — change both.
+    fn impl_type_name(&self, ty: Option<Node>) -> Option<String> {
+        let ty = ty?;
+        match ty.kind() {
+            "type_identifier" | "identifier" => Some(self.text(ty).to_string()),
+            "generic_type" => self.impl_type_name(ty.child_by_field_name("type")),
+            "scoped_type_identifier" | "scoped_identifier" => {
+                self.impl_type_name(ty.child_by_field_name("name"))
+            }
+            "reference_type" => self.impl_type_name(ty.child_by_field_name("type")),
+            _ => None,
+        }
+    }
+
+    /// rustExtractor.getReceiverType: parent-walk to the nearest impl_item and
+    /// read its `type` field (impl_type_name). The pre-#1588 rule took the
+    /// LAST direct type_identifier child, which for `impl Trait for Generic<T>`
+    /// was the TRAIT — so every parameterized impl's methods were qualified by
+    /// the trait.
     fn receiver_type_of(&self, node: Node) -> Option<String> {
         let mut parent = node.parent();
         while let Some(p) = parent {
             if p.kind() == "impl_item" {
-                let type_idents: Vec<Node> = (0..p.named_child_count())
-                    .filter_map(|i| p.named_child(i))
-                    .filter(|c| c.kind() == "type_identifier")
-                    .collect();
-                if let Some(last) = type_idents.last() {
-                    return Some(self.text(*last).to_string());
-                }
-                let generic = (0..p.named_child_count())
-                    .filter_map(|i| p.named_child(i))
-                    .find(|c| c.kind() == "generic_type");
-                if let Some(g) = generic {
-                    let inner = (0..g.named_child_count())
-                        .filter_map(|i| g.named_child(i))
-                        .find(|c| c.kind() == "type_identifier");
-                    if let Some(inner) = inner {
-                        return Some(self.text(inner).to_string());
-                    }
-                }
-                return None;
+                return self.impl_type_name(p.child_by_field_name("type"));
             }
             parent = p.parent();
         }
@@ -1024,36 +1027,19 @@ impl<'t> Walker<'t> {
         }
     }
 
-    /// extractRustImplItem — `impl Trait for Type` back-reference: positional
-    /// type-node filter (NEVER the grammar's trait:/type: fields), ≥2 needed,
-    /// target found by FIRST earlier node of kind struct/enum/class (never
-    /// trait); ref FROM the type's node, named by the trait's full text.
+    /// extractRustImplItem — `impl Trait for Type` back-reference from the
+    /// grammar's `trait` / `type` fields (#1588; an inherent impl has no
+    /// `trait` field and emits nothing). Target = FIRST earlier node of kind
+    /// struct/union/enum/class (never trait) named by impl_type_name; ref FROM
+    /// the type's node, named by the trait's full text (scoped path / generic
+    /// args kept), at the trait node's position.
     fn extract_rust_impl_item(&mut self, node: Node<'t>) {
-        let has_for = (0..node.child_count())
-            .filter_map(|i| node.child(i))
-            .any(|c| c.kind() == "for" && !c.is_named());
-        if !has_for {
+        let Some(trait_node) = node.child_by_field_name("trait") else {
             return;
-        }
-        let type_idents: Vec<Node> = (0..node.named_child_count())
-            .filter_map(|i| node.named_child(i))
-            .filter(|c| matches!(c.kind(), "type_identifier" | "generic_type" | "scoped_type_identifier"))
-            .collect();
-        if type_idents.len() < 2 {
-            return;
-        }
-        let trait_node = type_idents[0];
-        let type_node = type_idents[type_idents.len() - 1];
-
+        };
         let trait_name = self.text(trait_node).to_string();
-        let type_name = if type_node.kind() == "generic_type" {
-            (0..type_node.named_child_count())
-                .filter_map(|i| type_node.named_child(i))
-                .find(|c| c.kind() == "type_identifier")
-                .map(|c| self.text(c).to_string())
-                .unwrap_or_else(|| self.text(type_node).to_string())
-        } else {
-            self.text(type_node).to_string()
+        let Some(type_name) = self.impl_type_name(node.child_by_field_name("type")) else {
+            return;
         };
 
         let target_row = self

docs/design/rust-kernel-migration-plan.md

@@ -148,9 +148,11 @@ them are the ORIGINAL plan and carry expectations that measurement later correct
       tokio node sections IDENTICAL, small precision-positive edge churn only,
       full suite green), walker `codegraph-kernel/src/rustlang.rs` (survey
       artifact: rust-lang-kernel-port-checklist.md — isAsync dead-code,
-      impl-pushes-no-scope, trait-receiver bug on `impl Trait for Generic<T>`,
-      phantom const identifiers, use-binding triple emission, all preserved
-      bug-for-bug). Gates: parity sweeps **0 diffs** on ripgrep (101/101,
+      impl-pushes-no-scope, trait-receiver bug on `impl Trait for Generic<T>`
+      (fixed on both sides together in #1588 — receiver now comes from the
+      impl_item's `type` field), phantom const identifiers, use-binding
+      triple emission, all preserved bug-for-bug). Gates: parity sweeps
+      **0 diffs** on ripgrep (101/101,
       0 deferred) / tokio (790/790, 0 deferred) / rust-analyzer (1217/1488,
       0 diffs; 271 deferrals are token-macro-table sources — `T![~]`, `[$]` —
       that error on BOTH arms, grammar-inherent like fmt's C++ 42%); full-init

docs/design/rust-lang-kernel-port-checklist.md

@@ -89,18 +89,21 @@ Hooks PRESENT (port each exactly):
 - **getVisibility (rust.ts:74)** — direct child of type `visibility_modifier`:
   text `.includes('pub')` → `'public'` else `'private'`; no modifier →
   `'private'` (so `pub(crate)`/`pub(super)` are all `'public'`).
-- **getReceiverType (rust.ts:83)** — walk PARENT chain to the nearest
-  `impl_item`; there: filter DIRECT namedChildren of type `type_identifier`;
-  if ≥1, return the LAST one's source text (`source.substring(startIndex,
-  endIndex)` — UTF-16 units). If none, find the first `generic_type` child and
-  return its inner `type_identifier` text; else undefined. Never an impl parent
-  → undefined. QUIRK/BUG, PRESERVE: for `impl Trait for Generic<T>` the only
-  direct type_identifier is the TRAIT (probe: `impl Render for Container<T>` →
-  typeIdents=[`Render`] → receiver = **`Render`**, the trait name — methods get
-  qualifiedName `Render::render` and a contains edge from the trait node if one
-  exists in-file). `impl fmt::Display for Fields` is fine
-  (scoped_type_identifier isn't type_identifier → [Fields]). `impl<T>
-  Container<T>` → no direct type_identifiers → generic branch → `Container`.
+- **getReceiverType (rust.ts)** — walk PARENT chain to the nearest
+  `impl_item`; there, read the grammar's `type` field through
+  `rustImplTypeName` (kernel: `impl_type_name`): `type_identifier`/`identifier`
+  → text; `generic_type` → its `type` field (bare name, never the args);
+  `scoped_type_identifier`/`scoped_identifier` → its `name` field (last
+  segment); `reference_type` → its `type` field; anything else (tuple, `dyn`,
+  pointer, primitive, fn type) → undefined. Never an impl parent → undefined.
+  **Changed in #1588 on both sides together**: the original rule took the LAST
+  direct `type_identifier` child, so for `impl Trait for Generic<T>` /
+  `Parents<'a>` / `&Foo` the only bare identifier was the TRAIT's (probe:
+  `impl Render for Container<T>` → receiver **`Render`** → methods
+  `Render::render`, colliding with the trait declaration and feeding the
+  interface-impl synthesizer a phantom declaration). Now `Container`.
+  `impl fmt::Display for Fields` → `Fields`; `impl<T> Container<T>` →
+  `Container`; `impl Tr for m::Foo` → `Foo` (was: no receiver).
   Note `<T>` type_parameters is its own child, its inner T is NOT a direct
   impl child.
 - **extractImport (rust.ts:120)** — signature = trimmed full `use …;` text.
@@ -187,8 +190,9 @@ undefined; **no isConst means `const_item`/`static_item` extract as kind
   present AND not class-like — finds the FIRST node in `this.nodes` with
   `name === receiverType && filePath === this.filePath && kind ∈
   {struct,class,enum,trait}`. Source-order dependent: an impl ABOVE its struct
-  gets no contains edge. `impl Trait for Generic<T>` (receiver=trait bug) links
-  to the TRAIT node if it's in-file.** Then type annotations, decorators
+  gets no contains edge. Since #1588 `impl Trait for Generic<T>` links to the
+  implementing TYPE's node (it used to link to the TRAIT node, the receiver
+  bug).** Then type annotations, decorators
   (no-op), body walk with the method pushed.
 - **Nested `fn` inside an impl-method's body**: visitFunctionBody:5245 →
   named → extractFunction → getReceiverType walks parents THROUGH the outer fn

src/extraction/languages/rust.ts

@@ -32,6 +32,45 @@ function extractRustReturnType(node: SyntaxNode, source: string): string | undef
   return last === 'Self' ? 'self' : last;
 }
 
+/**
+ * The implementing type's simple name for an `impl` block, read from the
+ * grammar's `type` field (#1588). Mirrored byte-for-byte by the native
+ * kernel's `impl_type_name` (codegraph-kernel/src/rustlang.rs) — change both.
+ *
+ * `impl<T> Source for BufSource<T>`, `impl<'a> Iterator for Parents<'a>`,
+ * `impl Trait for &Foo`, `impl Trait for m::Foo` all yield the implementing
+ * TYPE (`BufSource`, `Parents`, `Foo`, `Foo`). The previous rule took the last
+ * bare `type_identifier` child of the `impl_item`; once the implementing type
+ * carries parameters it parses as a `generic_type`, so the only bare
+ * identifier left was the TRAIT's — every parameterized impl's methods were
+ * qualified by the trait (`Source::read`), unaddressable by their type and
+ * colliding with the trait's own declaration.
+ *
+ * Shapes that name no single type (tuples, `dyn Trait`, pointers, primitives,
+ * function types…) yield undefined: no receiver, and the fn is extracted
+ * exactly as before.
+ */
+export function rustImplTypeName(typeNode: SyntaxNode | null, source: string): string | undefined {
+  if (!typeNode) return undefined;
+  switch (typeNode.type) {
+    case 'type_identifier':
+    case 'identifier':
+      return getNodeText(typeNode, source);
+    // `Foo<T>` — the `type` field is the bare (or scoped) name, never the args.
+    case 'generic_type':
+      return rustImplTypeName(getChildByField(typeNode, 'type'), source);
+    // `m::Foo` — the last segment is the type's name.
+    case 'scoped_type_identifier':
+    case 'scoped_identifier':
+      return rustImplTypeName(getChildByField(typeNode, 'name'), source);
+    // `&Foo` / `&'a mut Foo` — the referenced type.
+    case 'reference_type':
+      return rustImplTypeName(getChildByField(typeNode, 'type'), source);
+    default:
+      return undefined;
+  }
+}
+
 export const rustExtractor: LanguageExtractor = {
   // `function_signature_item` is a trait method DECLARATION (`fn render(&self);`,
   // no body). Extracting it makes a trait's method set first-class, which
@@ -88,32 +127,10 @@ export const rustExtractor: LanguageExtractor = {
     let parent = node.parent;
     while (parent) {
       if (parent.type === 'impl_item') {
-        // For `impl Type { ... }` — the type is a direct type_identifier child
-        // For `impl Trait for Type { ... }` — the type is the LAST type_identifier
-        // (the first is part of the trait path)
-        const children = parent.namedChildren;
-        // Find all direct type_identifier children (not nested in scoped paths)
-        const typeIdents = children.filter(
-          (c: SyntaxNode) => c.type === 'type_identifier'
-        );
-        if (typeIdents.length > 0) {
-          // Last type_identifier is always the implementing type
-          const typeNode = typeIdents[typeIdents.length - 1]!;
-          return source.substring(typeNode.startIndex, typeNode.endIndex);
-        }
-        // Handle generic types: impl<T> MyStruct<T> { ... }
-        const genericType = children.find(
-          (c: SyntaxNode) => c.type === 'generic_type'
-        );
-        if (genericType) {
-          const innerType = genericType.namedChildren.find(
-            (c: SyntaxNode) => c.type === 'type_identifier'
-          );
-          if (innerType) {
-            return source.substring(innerType.startIndex, innerType.endIndex);
-          }
-        }
-        return undefined;
+        // The grammar names the implementing type directly (the `type` field)
+        // for both `impl Type { … }` and `impl Trait for Type { … }` — see
+        // rustImplTypeName for why the old positional scan was wrong (#1588).
+        return rustImplTypeName(getChildByField(parent, 'type'), source);
       }
       parent = parent.parent;
     }

src/extraction/tree-sitter.ts

@@ -22,6 +22,7 @@ import { isGeneratedFile } from './generated-detection';
 import type { LanguageExtractor, ExtractorContext } from './tree-sitter-types';
 import { EXTRACTORS } from './languages';
 import { stripCppTemplateArgs } from './languages/c-cpp';
+import { rustImplTypeName } from './languages/rust';
 import { LiquidExtractor } from './liquid-extractor';
 import { RazorExtractor } from './razor-extractor';
 import { SvelteExtractor } from './svelte-extractor';
@@ -5717,38 +5718,20 @@ export class TreeSitterExtractor {
    * For plain `impl Type { ... }` (no trait), no inheritance edge is needed.
    */
   private extractRustImplItem(node: SyntaxNode): void {
-    // Check if this is `impl Trait for Type` by looking for a `for` keyword
-    const hasFor = node.children.some(
-      (c: SyntaxNode) => c.type === 'for' && !c.isNamed
-    );
-    if (!hasFor) return;
-
-    // In `impl Trait for Type`, the type_identifiers are:
-    // first = Trait name, last = implementing Type name
-    // Also handle generic types like `impl<T> Trait for MyStruct<T>`
-    const typeIdents = node.namedChildren.filter(
-      (c: SyntaxNode) => c.type === 'type_identifier' || c.type === 'generic_type' || c.type === 'scoped_type_identifier'
-    );
-    if (typeIdents.length < 2) return;
-
-    const traitNode = typeIdents[0]!;
-    const typeNode = typeIdents[typeIdents.length - 1]!;
-
-    // Get the trait name (handle scoped paths like std::fmt::Display)
-    const traitName = traitNode.type === 'scoped_type_identifier'
-      ? this.source.substring(traitNode.startIndex, traitNode.endIndex)
-      : getNodeText(traitNode, this.source);
-
-    // Get the implementing type name (extract inner type_identifier for generics)
-    let typeName: string;
-    if (typeNode.type === 'generic_type') {
-      const inner = typeNode.namedChildren.find(
-        (c: SyntaxNode) => c.type === 'type_identifier'
-      );
-      typeName = inner ? getNodeText(inner, this.source) : getNodeText(typeNode, this.source);
-    } else {
-      typeName = getNodeText(typeNode, this.source);
-    }
+    // `impl Trait for Type` carries the trait in the grammar's `trait` field;
+    // an inherent `impl Type { … }` has none and needs no inheritance edge.
+    const traitNode = getChildByField(node, 'trait');
+    if (!traitNode) return;
+
+    // Full text, so a scoped path (`std::fmt::Display`) and a generic trait
+    // (`From<u32>`) keep their spelling.
+    const traitName = getNodeText(traitNode, this.source);
+
+    // The implementing type from the `type` field (#1588). The old positional
+    // scan took the LAST type-shaped child, which for a parameterized
+    // implementing type (`BufSource<T>`, `Parents<'a>`, `&Foo`) was the trait.
+    const typeName = rustImplTypeName(getChildByField(node, 'type'), this.source);
+    if (!typeName) return;
 
     // Find the struct/type node for the implementing type
     const typeNodeId = this.findNodeByName(typeName);