fix(registry): reject unreachable qualified fallbacks

When a dotted or namespace-qualified callee has import evidence but no candidate is import-reachable, stop before weak same-simple-name fallback.

This prevents external calls such as email.message.Message or receiver calls such as response.get from resolving to unrelated project symbols while preserving import_map, import_map_suffix, qualified_suffix, and bare-name fallback behavior.

Signed-off-by: Andrew Hundt <ATHundt@gmail.com>

src/pipeline/registry.c

@@ -104,6 +104,10 @@ static const char *simple_name(const char *qn) {
     return seg;
 }
 
+static bool callee_has_qualified_separator(const char *callee_name) {
+    return callee_name && (strchr(callee_name, '.') != NULL || strstr(callee_name, "::") != NULL);
+}
+
 /* Extract everything before the last dot. Returns heap-allocated string. */
 
 /* Check if a qualified name looks like a test/mock path. */
@@ -613,7 +617,8 @@ static cbm_resolution_t resolve_same_module(const cbm_registry_t *r, const char
 
 /* Strategy 4: multiple candidates with import filtering. */
 static cbm_resolution_t resolve_multi_with_imports(const qn_array_t *arr, const char *module_qn,
-                                                   const char **import_vals, int import_count) {
+                                                   const char **import_vals, int import_count,
+                                                   bool callee_qualified) {
     const char *filtered[CBM_SZ_256];
     int fcount = 0;
     for (int i = 0; i < arr->count && fcount < CBM_SZ_256; i++) {
@@ -632,7 +637,10 @@ static cbm_resolution_t resolve_multi_with_imports(const qn_array_t *arr, const
             return (cbm_resolution_t){best, "suffix_match", conf, fcount};
         }
     }
-    /* No import-reachable — use all candidates with penalty */
+    if (callee_qualified) {
+        return empty_result();
+    }
+    /* No import-reachable for a bare callee — use all candidates with penalty. */
     const char *best = best_by_import_distance((const char **)arr->items, arr->count, module_qn);
     if (best) {
         double conf = candidate_count_penalty(CONF_SUFFIX_MATCH * REG_HALF_PENALTY, arr->count);
@@ -672,7 +680,7 @@ static const char *qualified_suffix_match(const qn_array_t *arr, const char *cal
     dotted[w] = '\0';
     /* Must be qualified (contain a '.') — a bare name matches every candidate
      * and carries no disambiguating signal. */
-    if (!strchr(dotted, '.')) {
+    if (!callee_has_qualified_separator(dotted)) {
         return NULL;
     }
     const char *match = NULL;
@@ -733,7 +741,8 @@ static cbm_resolution_t resolve_name_lookup(const cbm_registry_t *r, const char
 
     /* Strategy 4: multiple candidates */
     if (import_vals && import_count > 0) {
-        return resolve_multi_with_imports(arr, module_qn, import_vals, import_count);
+        return resolve_multi_with_imports(arr, module_qn, import_vals, import_count,
+                                          callee_has_qualified_separator(callee_name));
     }
     const char *best = best_by_import_distance((const char **)arr->items, arr->count, module_qn);
     if (best) {

tests/test_registry.c

@@ -326,6 +326,40 @@ TEST(resolve_qualified_ambiguous_tail_falls_through) {
     PASS();
 }
 
+TEST(resolve_qualified_imported_external_rejects_unreachable_suffix) {
+    cbm_registry_t *r = cbm_registry_new();
+    cbm_registry_add(r, "Message", "proj.docs.additional.Message", "Class");
+    cbm_registry_add(r, "Message", "proj.models.Message", "Class");
+    cbm_registry_add(r, "Message", "proj.other.Message", "Class");
+
+    const char *keys[] = {"email.message"};
+    const char *vals[] = {"email.message"};
+    cbm_resolution_t res =
+        cbm_registry_resolve(r, "email.message.Message", "proj.fastapi.routing", keys, vals, 1);
+    ASSERT_TRUE(!res.qualified_name || res.qualified_name[0] == '\0');
+    ASSERT_TRUE(!res.strategy || res.strategy[0] == '\0');
+
+    cbm_registry_free(r);
+    PASS();
+}
+
+TEST(resolve_dotted_receiver_rejects_unreachable_suffix_when_imports_exist) {
+    cbm_registry_t *r = cbm_registry_new();
+    cbm_registry_add(r, "get", "proj.fastapi.routing.APIRouter.get", "Method");
+    cbm_registry_add(r, "get", "proj.datastructures.Headers.get", "Method");
+    cbm_registry_add(r, "get", "proj.other.Mapping.get", "Method");
+
+    const char *keys[] = {"Request"};
+    const char *vals[] = {"starlette.requests.Request"};
+    cbm_resolution_t res =
+        cbm_registry_resolve(r, "response.get", "proj.fastapi.routing", keys, vals, 1);
+    ASSERT_TRUE(!res.qualified_name || res.qualified_name[0] == '\0');
+    ASSERT_TRUE(!res.strategy || res.strategy[0] == '\0');
+
+    cbm_registry_free(r);
+    PASS();
+}
+
 TEST(resolve_import_map) {
     cbm_registry_t *r = cbm_registry_new();
     cbm_registry_add(r, "Process", "proj.pkg.worker.Process", "Function");
@@ -797,6 +831,8 @@ SUITE(registry) {
     RUN_TEST(resolve_same_module);
     RUN_TEST(resolve_qualified_disambiguates_same_name);
     RUN_TEST(resolve_qualified_ambiguous_tail_falls_through);
+    RUN_TEST(resolve_qualified_imported_external_rejects_unreachable_suffix);
+    RUN_TEST(resolve_dotted_receiver_rejects_unreachable_suffix_when_imports_exist);
     RUN_TEST(resolve_import_map);
     RUN_TEST(resolve_import_map_bare_function);
     RUN_TEST(resolve_unique_name);