fix(pipeline): a bare Go reference never binds a struct Field

The READS/WRITES resolvers and the USAGE registry fallback hand bare
reference text to the short-name registry, which contains Field nodes -
so once Go struct fields exist (#1935), every Go local err := ... binds
whichever struct field is named err, project-wide: 21308 USAGE and 5191
WRITES onto Go fields on the measured repo, top target a test struct's
field T collecting 3013 edges. In Go that binding is impossible by
construction: a field is only reachable through a selector expression
(x.f), and selector references resolve on the LSP path - every
Field-targeted reference edge in the census carried dot-less text.

Add cbm_go_suppress_bare_field_ref() next to the #1928 predicate and
consult it at the same four sites (both READS/WRITES resolvers, both
USAGE registry fallbacks): drop the bind when the file is Go, the
target label is Field, and the reference text has no '.'. Go-gated
because C#/Java/C++/Python method bodies legitimately reference their
own members bare (cp_reads_writes_cs_static_field pins that shape).

Field-validated on the #1940 stack: USAGE onto Go fields 21308 -> 0,
WRITES 5191 -> 0; the only remaining field-targeted edges are 2466
CALLS, which are #1906/#1907's selector-guard territory. Reproduce-
first pipeline probes (sequential + parallel twins) were RED on the
stack without this commit.

Fixes #1942

Signed-off-by: Ilya Brykau <ilya.brykau@orca.security>

src/pipeline/pass_parallel.c

@@ -2660,6 +2660,11 @@ static void resolve_file_usages(resolve_ctx_t *rc, resolve_worker_state_t *ws,
             if (tgt && cbm_suppress_cross_language_ref(lang, tgt->file_path)) {
                 continue;
             }
+            /* #1942: a bare Go reference can never denote a struct field. */
+            if (tgt &&
+                cbm_go_suppress_bare_field_ref(lang == CBM_LANG_GO, usage->ref_name, tgt->label)) {
+                continue;
+            }
             if (usage->semantic_reference_blocked && (usage->semantic_reference_local_shadow ||
                                                       cbm_pipeline_node_is_callable_target(tgt))) {
                 continue;
@@ -2745,6 +2750,10 @@ static void resolve_file_rw(resolve_ctx_t *rc, resolve_worker_state_t *ws, CBMFi
         if (cbm_suppress_cross_language_ref(lang, tgt->file_path)) {
             continue;
         }
+        /* #1942: a bare Go reference can never denote a struct field. */
+        if (cbm_go_suppress_bare_field_ref(lang == CBM_LANG_GO, rw->var_name, tgt->label)) {
+            continue;
+        }
         const char *etype = rw->is_write ? "WRITES" : "READS";
         cbm_gbuf_insert_edge(ws->local_edge_buf, src->id, tgt->id, etype, "{}");
     }

src/pipeline/pass_usages.c

@@ -216,6 +216,11 @@ static int resolve_usage_edges(cbm_pipeline_ctx_t *ctx, const CBMFileResult *res
             if (tgt && cbm_suppress_cross_language_ref(lang, tgt->file_path)) {
                 continue;
             }
+            /* #1942: a bare Go reference can never denote a struct field. */
+            if (tgt &&
+                cbm_go_suppress_bare_field_ref(lang == CBM_LANG_GO, usage->ref_name, tgt->label)) {
+                continue;
+            }
             if (usage->semantic_reference_blocked && (usage->semantic_reference_local_shadow ||
                                                       cbm_pipeline_node_is_callable_target(tgt))) {
                 continue;
@@ -304,6 +309,10 @@ static int resolve_rw_edges(cbm_pipeline_ctx_t *ctx, const CBMFileResult *result
         if (cbm_suppress_cross_language_ref(lang, tgt->file_path)) {
             continue;
         }
+        /* #1942: a bare Go reference can never denote a struct field. */
+        if (cbm_go_suppress_bare_field_ref(lang == CBM_LANG_GO, rw->var_name, tgt->label)) {
+            continue;
+        }
 
         const char *edge_type = rw->is_write ? "WRITES" : "READS";
         cbm_gbuf_insert_edge(ctx->gbuf, src->id, tgt->id, edge_type, "{}");

src/pipeline/pipeline.h

@@ -296,6 +296,14 @@ bool cbm_suppress_cross_language_suffix_match(CBMLanguage caller_lang, const cha
  * unit-tested in test_registry.c. */
 bool cbm_suppress_cross_language_ref(CBMLanguage caller_lang, const char *target_file_path);
 
+/* #1942: a bare (dot-less) Go reference can never denote a struct field —
+ * field access is always a selector expression, and selector references
+ * resolve on the LSP path. Drops a READS/WRITES/USAGE bind whose target is a
+ * Field when the reference text carries no '.'. Go only: other OO languages
+ * legitimately reference their own members bare inside method bodies. Pure;
+ * unit-tested in test_registry.c. */
+bool cbm_go_suppress_bare_field_ref(bool is_go, const char *ref_name, const char *target_label);
+
 /* Get the label of a qualified name, or NULL if not found. */
 const char *cbm_registry_label_of(const cbm_registry_t *r, const char *qn);
 

src/pipeline/registry.c

@@ -546,6 +546,24 @@ bool cbm_suppress_cross_language_ref(CBMLanguage caller_lang, const char *target
     return true;
 }
 
+bool cbm_go_suppress_bare_field_ref(bool is_go, const char *ref_name, const char *target_label) {
+    /* #1942: a bare (dot-less) Go reference can never denote a struct field —
+     * field access is always a selector expression (x.f), and selector
+     * references resolve through the LSP join, never through the bare-name
+     * registry fallback. Every Field-targeted reference edge in the field
+     * census carried dot-less text, so dropping the bind loses nothing real.
+     * Go-gated: a C#/Java/C++/Python method body legitimately references its
+     * own members bare (cp_reads_writes_cs_static_field pins that shape as
+     * required), so a global veto would break those languages. */
+    if (!is_go || !ref_name || !ref_name[0] || !target_label) {
+        return false;
+    }
+    if (strcmp(target_label, "Field") != 0) {
+        return false;
+    }
+    return strchr(ref_name, '.') == NULL;
+}
+
 /* ── Lifecycle ──────────────────────────────────────────────────── */
 
 cbm_registry_t *cbm_registry_new(void) {