Keep every method a duplicate index key maps to, not just the last one

A plain dict assignment silently overwrote an earlier target whenever
two method nodes shared both a source impl node and a stripped
label, which would have kept whichever one was seen last instead of
surfacing the case as the ambiguity it is. The index now keeps a set
per key and folds every match into the candidate set before the
exactly one candidate check runs, so a genuine duplicate still bails
instead of guessing.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
(cherry picked from commit 2cbbf1a670)

graphify/extract.py

@@ -4758,8 +4758,12 @@ def _resolve_rust_self_member_calls(
         if str(n.get("source_file") or "").endswith(".rs"):
             nids_by_label.setdefault(n.get("label", ""), []).append(n.get("id"))
 
-    # (impl/type node id, bare method name) -> method node id, from `method` edges.
-    method_index: dict[tuple[str, str], str] = {}
+    # (impl/type node id, bare method name) -> method node id(s), from `method`
+    # edges. A set, not a single overwritten value: two distinct method nodes
+    # sharing both a source and a stripped label (however unlikely) must still
+    # surface as an ambiguity below rather than silently keeping whichever one
+    # was seen last.
+    method_index: dict[tuple[str, str], set[str]] = {}
     for e in all_edges:
         if e.get("relation") != "method":
             continue
@@ -4767,7 +4771,7 @@ def _resolve_rust_self_member_calls(
         tnode = node_by_id.get(tgt)
         if tnode is not None:
             name = str(tnode.get("label", "")).strip("()").lstrip(".")
-            method_index[(src, name)] = tgt
+            method_index.setdefault((src, name), set()).add(tgt)
 
     # Scoped to `calls`: a caller that already has a DIFFERENT relation to the
     # same target (e.g. a `references` edge from also naming the type in a
@@ -4781,11 +4785,9 @@ def _resolve_rust_self_member_calls(
     for rc in raw:
         caller = rc["caller_nid"]
         callee = rc["callee"]
-        candidates = {
-            method_index[(nid, callee)]
-            for nid in nids_by_label.get(rc["rust_self_type"], [])
-            if (nid, callee) in method_index
-        }
+        candidates: set[str] = set()
+        for nid in nids_by_label.get(rc["rust_self_type"], []):
+            candidates |= method_index.get((nid, callee), set())
         if len(candidates) != 1:  # zero or ambiguous -> no edge (god-node guard)
             continue
         tgt = next(iter(candidates))

tests/test_rust_self_member_calls.py

@@ -168,3 +168,39 @@ def test_resolver_is_not_suppressed_by_an_unrelated_edge_to_the_same_pair(tmp_pa
         if e["relation"] == "calls"
     }
     assert ("impl_foo_caller", "impl_foo_method") in calls
+
+
+def test_resolver_treats_a_duplicate_method_index_key_as_ambiguous(tmp_path: Path):
+    """Two DIFFERENT method nodes sharing both a source impl node and a
+    stripped label must surface as an ambiguity (no edge), not silently
+    keep whichever one a plain dict overwrite happened to see last."""
+    from graphify.extract import _resolve_rust_self_member_calls
+
+    all_nodes = [
+        {"id": "impl_foo", "label": "Foo", "source_file": "a.rs"},
+        {"id": "impl_foo_method_a", "label": ".method()", "source_file": "a.rs"},
+        {"id": "impl_foo_method_b", "label": ".method()", "source_file": "a.rs"},
+        {"id": "impl_foo_caller", "label": ".caller()", "source_file": "a.rs"},
+    ]
+    all_edges = [
+        {"source": "impl_foo", "target": "impl_foo_method_a", "relation": "method"},
+        {"source": "impl_foo", "target": "impl_foo_method_b", "relation": "method"},
+    ]
+    per_file = [{
+        "raw_calls": [{
+            "caller_nid": "impl_foo_caller",
+            "callee": "method",
+            "rust_self_type": "Foo",
+            "source_file": "a.rs",
+            "source_location": "L1",
+        }],
+    }]
+
+    _resolve_rust_self_member_calls(per_file, all_nodes, all_edges)
+
+    calls = {
+        (e["source"], e["target"])
+        for e in all_edges
+        if e["relation"] == "calls"
+    }
+    assert not calls, "two same-labeled method nodes on one type must not guess"