fix(pipeline): suppress weak short-name matches for Go selector calls

internal/cbm/extract_calls.c

@@ -4493,6 +4493,24 @@ CBMInvocationDescriptor handle_calls(CBMExtractCtx *ctx, TSNode node, const CBML
                     }
                 }
             }
+            // Go receiver-aware guard (same direction as the TS/JS flag above).
+            // Flag a selector call x.foo(). The Go AST cannot separate a method
+            // call on a value from a package-qualified call — but every selector
+            // call the Go LSP or the import/qualified registry strategies CAN
+            // place never reaches the weak short-name guards, so the flag only
+            // bites on unresolvable receivers (`f.Close()` on an os.File,
+            // `sha256.New()` behind an unindexed import), where a project-wide
+            // short-name match fabricates an edge to an unrelated project
+            // symbol sharing the name. Bare calls (helper()) keep
+            // is_method=false and resolve same-module/import paths as before.
+            if (ctx->language == CBM_LANG_GO &&
+                strcmp(ts_node_type(node), "call_expression") == 0) {
+                TSNode gofn = ts_node_child_by_field_name(node, TS_FIELD("function"));
+                if (!ts_node_is_null(gofn) &&
+                    strcmp(ts_node_type(gofn), "selector_expression") == 0) {
+                    call.is_method = true;
+                }
+            }
 
             TSNode args = ts_node_child_by_field_name(node, TS_FIELD("arguments"));
             /* tree-sitter-elixir attaches NO field name to a call's arguments

src/pipeline/pass_calls.c

@@ -1116,7 +1116,13 @@ static int resolve_single_call(cbm_pipeline_ctx_t *ctx, CBMCall *call, const CBM
      * language gated on only one resolver produces an edge on the sequential
      * path and not the parallel one (or vice versa), breaking MT determinism.
      * ArkTS belongs to the JS/TS family here (#1842); dropping it would
-     * reintroduce the #592/#606 false-edge class for .ets files. */
+     * reintroduce the #592/#606 false-edge class for .ets files.
+     *
+     * Go (#1906) rides the same deferred-drop plumbing through its OWN
+     * predicate: its drop-list differs (field_type_hint is receiver-aware for
+     * Go, and unique_name drops only when import-unreachability-penalized), so
+     * it composes via cbm_go_suppress_weak_method_match instead of widening
+     * the shared gate. Same lockstep rule: mirror pass_parallel.c. */
     bool suppress_weak_member = lang == CBM_LANG_PYTHON || lang == CBM_LANG_JAVASCRIPT ||
                                 lang == CBM_LANG_TYPESCRIPT || lang == CBM_LANG_TSX ||
                                 lang == CBM_LANG_ARKTS ||
@@ -1144,6 +1150,8 @@ static int resolve_single_call(cbm_pipeline_ctx_t *ctx, CBMCall *call, const CBM
                                              res.strategy)) ||
         cbm_suppress_weak_local_binding_call(suppress_weak_local_binding,
                                              call->callee_is_locally_bound, res.strategy) ||
+        cbm_go_suppress_weak_method_match(lang == CBM_LANG_GO, call->is_method, res.strategy,
+                                          res.confidence) ||
         /* Import-binding suppression (#2127): an external `from m import f`
          * binds `f` for the whole module, so a weak short-name match onto a
          * project `X.f` outside m is fabricated. Python-only (the import

src/pipeline/pass_parallel.c

@@ -3348,7 +3348,15 @@ static void resolve_file_calls(resolve_ctx_t *rc, resolve_worker_state_t *ws, CB
         }
 
         _rc_t0 = extract_now_ns();
-        try_field_type_hint(rc, &res, call->callee_name, source_node->id);
+        /* Not for Go (F-G9): the hint matches the capitalized receiver
+         * VARIABLE name as a substring of a candidate QN (`t.Run` -> any
+         * `...T...Run`), with no type evidence. The sequential resolver has no
+         * such step, so for Go it produced parallel-only edges (par/seq CALLS
+         * diverged), and the Go selector guard could not see them as the weak
+         * pick they are. SCIP precision of Go field_type_hint: 0.016. */
+        if (lang != CBM_LANG_GO) {
+            try_field_type_hint(rc, &res, call->callee_name, source_node->id);
+        }
         /* Cross-language veto — the same predicate as pass_calls.c, applied
          * AFTER the field-type hint so the hint may still re-pick a compatible
          * candidate first, and BEFORE the empty-resolution fallbacks below so a
@@ -3385,7 +3393,9 @@ static void resolve_file_calls(resolve_ctx_t *rc, resolve_worker_state_t *ws, CB
          * #606 direction.
          *
          * This language set MUST match the one in pass_calls.c exactly — see the
-         * note there. ArkTS belongs to the JS/TS family (#1842). */
+         * note there. ArkTS belongs to the JS/TS family (#1842). Go (#1906)
+         * composes via its own predicate (different drop-list — see
+         * cbm_go_suppress_weak_method_match), mirrored in pass_calls.c. */
         bool suppress_weak_member = lang == CBM_LANG_PYTHON || lang == CBM_LANG_JAVASCRIPT ||
                                     lang == CBM_LANG_TYPESCRIPT || lang == CBM_LANG_TSX ||
                                     lang == CBM_LANG_ARKTS ||
@@ -3403,6 +3413,8 @@ static void resolve_file_calls(resolve_ctx_t *rc, resolve_worker_state_t *ws, CB
                                                  call->callee_name, res.strategy)) ||
             cbm_suppress_weak_local_binding_call(suppress_weak_local_binding,
                                                  call->callee_is_locally_bound, res.strategy) ||
+            cbm_go_suppress_weak_method_match(lang == CBM_LANG_GO, call->is_method, res.strategy,
+                                              res.confidence) ||
             /* Import-binding suppression (#2127) — see pass_calls.c; this gate
              * MUST stay identical to the one there. */
             (lang == CBM_LANG_PYTHON &&

src/pipeline/pipeline.h

@@ -412,6 +412,15 @@ bool cbm_weak_member_unique_name_exempt(bool is_python, bool receiver_is_self_at
 bool cbm_suppress_weak_local_binding_call(bool enabled, bool callee_is_locally_bound,
                                           const char *strategy);
 
+/* Go analog of the TS/JS guard, same failure class: a selector call whose
+ * receiver the Go LSP could not type must not be bound by a receiver-blind
+ * short-name strategy. Drops suffix_match / fuzzy always, and unique_name only
+ * when its confidence is import-unreachability-penalized (the stdlib/vendor
+ * hijack shape). field_type_hint is deliberately NOT dropped for Go — struct
+ * fields carry declared types, so the hint is receiver-aware there. */
+bool cbm_go_suppress_weak_method_match(bool is_go, bool is_method, const char *strategy,
+                                       double confidence);
+
 /* Import-binding counterpart (#2127). True when the callee's root identifier
  * is bound by an import of this file whose module chain contradicts the
  * resolved target (`from unittest.mock import patch; patch()` must not bind a

src/pipeline/registry.c

@@ -750,6 +750,35 @@ bool cbm_suppress_weak_local_binding_call(bool enabled, bool callee_is_locally_b
     return weak_short_name_strategy(strategy);
 }
 
+bool cbm_go_suppress_weak_method_match(bool is_go, bool is_method, const char *strategy,
+                                       double confidence) {
+    /* Go analog of the TS/JS guard above, same failure class: a selector call
+     * whose receiver the Go LSP could not type reaches the registry and a bare
+     * short-name strategy binds it to an arbitrary same-named project symbol
+     * (`f.Close()` on an os.File -> a project `Close`, suffix_match over 15
+     * candidates). Built on the shared drop-list so "weak" means one thing
+     * for every guard; Go narrows it in one place only (unique_name below).
+     * field_type_hint stays weak: it is a receiver-NAME substring match, not
+     * a declared-type lookup (the parallel resolver no longer produces it for
+     * Go; a typed field call such as lrp_go_s8's `s.repo.Find()` resolves
+     * through the Go LSP). */
+    if (!is_go || !is_method || !weak_short_name_strategy(strategy)) {
+        return false;
+    }
+    if (strcmp(strategy, "unique_name") != 0) {
+        return true; /* suffix_match, field_type_hint, fuzzy */
+    }
+    /* unique_name is dropped only when PENALIZED: resolve_name_lookup scales
+     * CONF_UNIQUE_NAME by DEFAULT_CONFIDENCE exactly when the lone candidate
+     * is not reachable through the caller's imports — the stdlib/vendor
+     * hijack shape (`io.Copy` -> a project `Copy`). An unpenalized
+     * unique_name target sits inside the caller's import closure (or the
+     * file has no imports, e.g. a same-package call) and must be kept —
+     * dropping it kills genuinely-typed lone-candidate calls that never
+     * enter the field-type-hint upgrade (candidate_count == 1). */
+    return confidence < CONF_UNIQUE_NAME;
+}
+
 /* Import-binding counterpart of the parameter guard above (#2127). An import
  * binds the identifier for the whole module; when that import is external it
  * never materializes, and the chain falls through to project-wide short-name

tests/test_extraction.c

@@ -7353,12 +7353,17 @@ TEST(extract_rust_generic_impl_call_scope_matches_def) {
     PASS();
 }
 
-/* Languages OUTSIDE the is_method flag set (only Perl and TS/JS/TSX set it) must
- * be unaffected: a Go method call never sets is_method. */
+/* Languages OUTSIDE the is_method flag set (Perl, Python, TS/JS/TSX and Go set
+ * it) must be unaffected: a Rust method call never sets is_method. */
 TEST(extract_flag_exempt_method_call_not_flagged_is_method) {
-    CBMFileResult *r = extract("package m\n"
-                               "func run(o Obj) { o.Commit(); helper() }\n",
-                               CBM_LANG_GO, "t", "x.go");
+    /* Rust is flag-exempt: only Perl, Python, TS/JS and Go set is_method.
+     * Guards the blast radius of the receiver-aware flags for every other
+     * language. */
+    CBMFileResult *r = extract("fn run(o: Obj) {\n"
+                               "    o.commit();\n"
+                               "    helper();\n"
+                               "}\n",
+                               CBM_LANG_RUST, "t", "x.rs");
     ASSERT_NOT_NULL(r);
     ASSERT_FALSE(r->has_error);
     for (int i = 0; i < r->calls.count; i++) {
@@ -7516,6 +7521,33 @@ TEST(extract_python_bare_call_flags_locally_bound_callee) {
     PASS();
 }
 
+TEST(extract_go_selector_call_flags_is_method) {
+    /* Go selector calls are flagged so the weak-match guard can fire when the
+     * Go LSP cannot type the receiver; bare calls stay unflagged. */
+    CBMFileResult *r = extract("package m\n"
+                               "func run(o Obj) { o.Commit(); helper() }\n",
+                               CBM_LANG_GO, "t", "x.go");
+    ASSERT_NOT_NULL(r);
+    ASSERT_FALSE(r->has_error);
+    bool saw_selector = false;
+    bool saw_bare = false;
+    for (int i = 0; i < r->calls.count; i++) {
+        const CBMCall *c = &r->calls.items[i];
+        if (c->callee_name && strstr(c->callee_name, "Commit") != NULL) {
+            ASSERT_TRUE(c->is_method);
+            saw_selector = true;
+        }
+        if (c->callee_name && strcmp(c->callee_name, "helper") == 0) {
+            ASSERT_FALSE(c->is_method);
+            saw_bare = true;
+        }
+    }
+    ASSERT_TRUE(saw_selector);
+    ASSERT_TRUE(saw_bare);
+    cbm_free_result(r);
+    PASS();
+}
+
 /* The bare-call flag is DEPTH-INDEPENDENT, and the binding is UNWOUND when its
  * scope closes.
  *
@@ -12728,6 +12760,7 @@ SUITE(extraction) {
     RUN_TEST(extract_python_member_call_flags_is_method);
     RUN_TEST(extract_python_bare_call_flags_locally_bound_callee);
     RUN_TEST(extract_python_bare_call_flag_is_depth_independent);
+    RUN_TEST(extract_go_selector_call_flags_is_method);
     RUN_TEST(extract_ts_member_call_flags_is_method);
     RUN_TEST(extract_ts_this_super_receiver_not_flagged);
     RUN_TEST(extract_js_member_call_flags_is_method);