feat(detection-core): unique-declaration member-call binding (8.2 final gated round step 1-2)

x.method() with a variable receiver binds complete iff exactly one same-name
method declaration exists repository-wide; collisions stay a finite candidate
set (receiver_type_unknown) and module-level functions never bind. Authorized
by maintainer strategy-review 2026-10-31; gated by dev-pool FA non-regression.

src/openultrasast/semantic/obligations/resolution.py

@@ -239,7 +239,15 @@ def _type_receiver_targets(same_name: tuple[SymbolId, ...], type_name: str, arit
 
 
 def _variable_receiver_targets(same_name: tuple[SymbolId, ...], arity: int | None) -> CallTargetSet:
+    # A variable receiver's type is unknown, but when exactly ONE method with the
+    # called name exists repository-wide, no second repository-defined target can
+    # exist, so the call binds complete (unique-declaration member-call binding).
+    # Two or more same-name declarations are a collision: they stay a finite
+    # candidate set, never a bare-name merge. A same-name module-level function is
+    # not a member-call target, so it neither binds nor collides here.
     methods = tuple(symbol for symbol in same_name if symbol.enclosing_type is not None)
+    if len(methods) == 1:
+        return CallTargetSet(targets=methods, completeness=Completeness(is_complete=True))
     narrowed = _arity_narrow(methods, arity)
     if not narrowed:
         return CallTargetSet(targets=(), completeness=Completeness(is_complete=False, reasons=("resolution:no_candidate",)))

tests/test_call_resolution.py

@@ -135,6 +135,47 @@ class TestResolveCall:
         assert len(candidates.targets) == 2
         assert candidates.completeness.reasons
 
+    def test_unique_declaration_member_call_binds_complete(self) -> None:
+        index = index_of(
+            (
+                "src/a/Store.java",
+                """public class Store {
+    public void persist(String item) { }
+}
+""",
+                "java",
+            )
+        )
+        call = _call(name="persist", line=1, receiver="store", arity=1)
+        target_set = resolve_call(call, module="src/a/Use.java", index=index)
+        assert target_set.targets == (SymbolId("src/a/Store.java", "Store", "persist", ("item",)),)
+        assert target_set.completeness.reasons == ()
+
+    def test_member_call_collision_across_modules_stays_incomplete(self) -> None:
+        index = index_of(
+            ("src/a/One.java", "public class Store { public void persist(String item) { } }", "java"),
+            ("src/b/Two.java", "public class Vault { public void persist(String item) { } }", "java"),
+        )
+        call = _call(name="persist", line=1, receiver="obj", arity=1)
+        target_set = resolve_call(call, module="src/a/One.java", index=index)
+        assert len(target_set.targets) == 2
+        assert target_set.completeness.reasons == ("resolution:receiver_type_unknown",)
+
+    def test_member_call_never_binds_module_level_function(self) -> None:
+        index = index_of(
+            (
+                "src/svc.py",
+                """def persist(item):
+    pass
+""",
+                "python",
+            )
+        )
+        call = _call(name="persist", line=3, receiver="obj", arity=1)
+        target_set = resolve_call(call, module="src/svc.py", index=index)
+        assert target_set.targets == ()
+        assert target_set.completeness.reasons
+
     def test_no_candidate_is_unresolved_with_reason(self) -> None:
         index = index_of(JAVA_ONE_CLASS)
         call = _call(name="missing", line=3, receiver="helper", arity=1)
@@ -233,6 +274,26 @@ class TestBindCalls:
         assert bindings.exact_callers(target) == ()
         assert bindings.counts["incomplete_calls"] == 1
 
+    def test_unique_declaration_member_call_counts_complete(self) -> None:
+        index = index_of(
+            (
+                "src/a/Store.java",
+                """public class Store {
+    public void persist(String item) { }
+}
+""",
+                "java",
+            )
+        )
+        bindings = bind_calls(
+            functions_by_module={"src/a/Use.java": (_ir_stub(calls=(_call(name="persist", line=2, receiver="store", arity=1),)),)},
+            index=index,
+        )
+        target = SymbolId("src/a/Store.java", "Store", "persist", ("item",))
+        assert bindings.exact_callers(target) == (CallerBinding(module="src/a/Use.java", function="caller", line=2, exact=True),)
+        assert bindings.counts["complete_calls"] == 1
+        assert bindings.counts["incomplete_calls"] == 0
+
 
 def _ir_stub(calls: tuple[CallSite, ...], name: str = "caller") -> FunctionIR:
     return FunctionIR(name=name, params=(), start_line=1, end_line=9, binds=(), calls=calls)

tests/test_obligation_summaries.py

@@ -540,6 +540,10 @@ JAVA_AUDITOR = """class Auditor {
     public void check() {
     }
 }
+class Gate {
+    public void check() {
+    }
+}
 """