fix(pipeline): key the Go Field guard on the recorded selector shape, not reference text

internal/cbm/cbm.h

@@ -292,6 +292,10 @@ typedef struct {
     uint32_t site_start_byte;             // exact reference-token span; end > start when present
     uint32_t site_end_byte;               // exclusive byte offset in the source file
     CBMSourceOrigin source_origin;        // raw source or C-family preprocessed buffer
+    bool is_member_access;                // token is the member half of a selector/attribute
+                                          // (Go x.f — field_identifier). The extractor strips
+                                          // the receiver, so this is the only surviving record
+                                          // of selector shape (#1962). Default false.
 } CBMUsage;
 
 typedef struct {
@@ -303,6 +307,9 @@ typedef struct {
     const char *var_name;          // variable name
     const char *enclosing_func_qn; // QN of enclosing function
     bool is_write;                 // true = write, false = read
+    bool is_member_access;         // var_name is the field half of a selector/member LHS
+                                   // (`t.err = x` → "err"); the receiver is stripped here,
+                                   // so this is the only record of selector shape (#1962)
 } CBMReadWrite;
 
 typedef struct {

internal/cbm/extract_semantic.c

@@ -146,7 +146,10 @@ static void walk_throws(CBMExtractCtx *ctx, TSNode root, const CBMLangSpec *spec
 //   - field/member/selector access (`self.total = ...`, `obj.Field = ...` →
 //     write the trailing field name `total`/`Field`)
 // Returns NULL if no simple write target can be determined.
-static char *resolve_lhs_write_name(CBMExtractCtx *ctx, TSNode left) {
+// Sets *is_member_out when the written name is the field half of a
+// member/selector LHS — the receiver is stripped from the returned name, so
+// this out-param is the only surviving record of the selector shape (#1962).
+static char *resolve_lhs_write_name(CBMExtractCtx *ctx, TSNode left, bool *is_member_out) {
     // Unwrap a single-element expression_list (Go).
     if (strcmp(ts_node_type(left), "expression_list") == 0) {
         if (ts_node_named_child_count(left) != 1) {
@@ -184,6 +187,9 @@ static char *resolve_lhs_write_name(CBMExtractCtx *ctx, TSNode left) {
             fld = ts_node_child_by_field_name(left, TS_FIELD("name"));
         }
         if (!ts_node_is_null(fld)) {
+            if (is_member_out) {
+                *is_member_out = true;
+            }
             return cbm_node_text(ctx->arena, fld, ctx->source);
         }
         return NULL;
@@ -251,12 +257,14 @@ static void try_emit_assignment_write(CBMExtractCtx *ctx, TSNode node, const cha
     if (ts_node_is_null(left)) {
         return;
     }
-    char *name = resolve_lhs_write_name(ctx, left);
+    bool is_member = false;
+    char *name = resolve_lhs_write_name(ctx, left, &is_member);
     if (name && name[0] && !cbm_is_keyword(name, ctx->language)) {
         CBMReadWrite rw;
         rw.var_name = name;
         rw.is_write = true;
         rw.enclosing_func_qn = func_qn;
+        rw.is_member_access = is_member;
         cbm_rw_push(&ctx->result->rw, ctx->arena, rw);
     }
 }
@@ -329,12 +337,14 @@ void handle_readwrites(CBMExtractCtx *ctx, TSNode node, const CBMLangSpec *spec,
         TSNode left = resolve_write_lhs_node(node);
 
         if (!ts_node_is_null(left)) {
-            char *name = resolve_lhs_write_name(ctx, left);
+            bool is_member = false;
+            char *name = resolve_lhs_write_name(ctx, left, &is_member);
             if (name && name[0] && !cbm_is_keyword(name, ctx->language)) {
                 CBMReadWrite rw;
                 rw.var_name = name;
                 rw.is_write = true;
                 rw.enclosing_func_qn = state->enclosing_func_qn;
+                rw.is_member_access = is_member;
                 cbm_rw_push(&ctx->result->rw, ctx->arena, rw);
             }
         }

internal/cbm/extract_usages.c

@@ -2673,6 +2673,10 @@ void handle_usages(CBMExtractCtx *ctx, TSNode node, const CBMLangSpec *spec, Wal
         usage.ref_name = name;
         usage.enclosing_func_qn = state->enclosing_func_qn;
         usage.lexical_scope_id = usage_lexical_scope_id_for_node(ctx, state, node);
+        /* The member half of a selector is its own reference node
+         * (field_identifier); record that shape — the name alone cannot carry
+         * it, and the Go Field guard keys on it (#1962). */
+        usage.is_member_access = strcmp(ts_node_type(node), "field_identifier") == 0;
         stamp_usage_site(ctx, &usage, node, name, state);
         cbm_usages_push(&ctx->result->usages, ctx->arena, usage);
     }

src/pipeline/pass_parallel.c

@@ -2670,9 +2670,10 @@ 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)) {
+            /* #1942/#1962: a bare Go reference can never denote a struct
+             * field; the member half of a selector may. */
+            if (tgt && cbm_go_suppress_bare_field_ref(lang == CBM_LANG_GO, usage->is_member_access,
+                                                      tgt->label)) {
                 continue;
             }
             if (usage->semantic_reference_blocked && (usage->semantic_reference_local_shadow ||
@@ -2760,8 +2761,9 @@ 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)) {
+        /* #1942/#1962: a bare Go reference can never denote a struct field;
+         * a selector-LHS write (`t.err = x`) may bind it. */
+        if (cbm_go_suppress_bare_field_ref(lang == CBM_LANG_GO, rw->is_member_access, tgt->label)) {
             continue;
         }
         const char *etype = rw->is_write ? "WRITES" : "READS";

src/pipeline/pass_usages.c

@@ -216,9 +216,10 @@ 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)) {
+            /* #1942/#1962: a bare Go reference can never denote a struct
+             * field; the member half of a selector may. */
+            if (tgt && cbm_go_suppress_bare_field_ref(lang == CBM_LANG_GO, usage->is_member_access,
+                                                      tgt->label)) {
                 continue;
             }
             if (usage->semantic_reference_blocked && (usage->semantic_reference_local_shadow ||
@@ -309,8 +310,9 @@ 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)) {
+        /* #1942/#1962: a bare Go reference can never denote a struct field;
+         * a selector-LHS write (`t.err = x`) may bind it. */
+        if (cbm_go_suppress_bare_field_ref(lang == CBM_LANG_GO, rw->is_member_access, tgt->label)) {
             continue;
         }
 

src/pipeline/pipeline.h

@@ -302,7 +302,7 @@ bool cbm_suppress_cross_language_ref(CBMLanguage caller_lang, const char *target
  * 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);
+bool cbm_go_suppress_bare_field_ref(bool is_go, bool is_member_access, 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

@@ -546,22 +546,21 @@ 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) {
+bool cbm_go_suppress_bare_field_ref(bool is_go, bool is_member_access, const char *target_label) {
+    /* #1942/#1962: a bare Go identifier can never denote a struct field —
+     * field access is always a selector expression (x.f). The extractor
+     * strips the receiver before the resolver runs (resolve_lhs_write_name
+     * records the trailing field name; is_reference_node records the inner
+     * field_identifier), so the reference TEXT is always dot-less and cannot
+     * carry the distinction — the recorded is_member_access shape can. Only a
+     * reference that was never the member half of a selector is refused a
+     * Field bind. 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 || is_member_access || !target_label) {
         return false;
     }
-    if (strcmp(target_label, "Field") != 0) {
-        return false;
-    }
-    return strchr(ref_name, '.') == NULL;
+    return strcmp(target_label, "Field") == 0;
 }
 
 /* ── Lifecycle ──────────────────────────────────────────────────── */

tests/test_pipeline.c

@@ -4857,6 +4857,17 @@ static void write_go_bare_field_fixture(const char *tmp, int pad_files) {
                     "\terr := errors.New(\"x\")\n"
                     "\treturn err\n"
                     "}\n");
+    /* #1962: genuine selector references from a sibling file of the same
+     * package. `t.err = nil` writes the field through a selector; `t.n` reads
+     * it. The extractor strips the receiver on both paths, so only the
+     * is_member_access signal can distinguish these from Run's bare local. */
+    write_temp_file(tmp, "state/reset.go",
+                    "package state\n"
+                    "\n"
+                    "func (t *Tracker) Reset() int {\n"
+                    "\tt.err = nil\n"
+                    "\treturn t.n\n"
+                    "}\n");
     for (int i = 0; i < pad_files; i++) {
         char name[64];
         char body[128];
@@ -4896,6 +4907,11 @@ TEST(pipeline_go_bare_ref_never_binds_field) {
     ASSERT_FALSE(cross_file_edge_exists(s, project, "Run", "err", "WRITES"));
     ASSERT_FALSE(cross_file_edge_exists(s, project, "Run", "err", "READS"));
     ASSERT_FALSE(cross_file_edge_exists(s, project, "Run", "err", "USAGE"));
+    /* #1962, reproduce-first: RED while the guard is a blanket veto — genuine
+     * selector references must reach the field (write via `t.err = nil`,
+     * value use via `t.n`). */
+    ASSERT_TRUE(cross_file_edge_exists(s, project, "Reset", "err", "WRITES"));
+    ASSERT_TRUE(cross_file_edge_exists(s, project, "Reset", "n", "USAGE"));
 
     cbm_store_close(s);
     cbm_pipeline_free(p);
@@ -4927,6 +4943,10 @@ TEST(pipeline_go_bare_ref_never_binds_field_parallel) {
     ASSERT_FALSE(cross_file_edge_exists(s, project, "Run", "err", "WRITES"));
     ASSERT_FALSE(cross_file_edge_exists(s, project, "Run", "err", "READS"));
     ASSERT_FALSE(cross_file_edge_exists(s, project, "Run", "err", "USAGE"));
+    /* #1962 parallel twin: resolve_file_rw / resolve_file_usages must honour
+     * the member-access signal exactly like the sequential resolvers. */
+    ASSERT_TRUE(cross_file_edge_exists(s, project, "Reset", "err", "WRITES"));
+    ASSERT_TRUE(cross_file_edge_exists(s, project, "Reset", "n", "USAGE"));
 
     cbm_store_close(s);
     cbm_pipeline_free(p);

tests/test_registry.c

@@ -840,22 +840,23 @@ TEST(cross_language_ref_drops_go_vs_c) {
 }
 
 TEST(go_bare_ref_never_binds_field) {
-    /* #1942: a bare (dot-less) Go reference can never denote a struct field —
-     * field access is always a selector expression. */
-    ASSERT_TRUE(cbm_go_suppress_bare_field_ref(true, "err", "Field"));
-    ASSERT_TRUE(cbm_go_suppress_bare_field_ref(true, "config", "Field"));
-    /* A selector-shaped reference may bind a field. */
-    ASSERT_FALSE(cbm_go_suppress_bare_field_ref(true, "t.err", "Field"));
+    /* #1942/#1962: a bare Go identifier can never denote a struct field —
+     * field access is always a selector expression. The extractor strips the
+     * receiver before the resolver runs (resolve_lhs_write_name writes the
+     * trailing name; is_reference_node records the inner field_identifier),
+     * so the selector-vs-bare distinction arrives as the recorded
+     * is_member_access signal, never as a dot in the reference text. */
+    ASSERT_TRUE(cbm_go_suppress_bare_field_ref(true, false, "Field"));
+    /* The member half of a selector may bind a field. */
+    ASSERT_FALSE(cbm_go_suppress_bare_field_ref(true, true, "Field"));
     /* Bare references to non-fields are untouched. */
-    ASSERT_FALSE(cbm_go_suppress_bare_field_ref(true, "err", "Variable"));
-    ASSERT_FALSE(cbm_go_suppress_bare_field_ref(true, "err", "Function"));
+    ASSERT_FALSE(cbm_go_suppress_bare_field_ref(true, false, "Variable"));
+    ASSERT_FALSE(cbm_go_suppress_bare_field_ref(true, false, "Function"));
     /* Other languages reference their own members bare inside methods —
      * never suppressed (cp_reads_writes_cs_static_field pins the C# shape). */
-    ASSERT_FALSE(cbm_go_suppress_bare_field_ref(false, "_count", "Field"));
-    /* Degenerate inputs → nothing to judge. */
-    ASSERT_FALSE(cbm_go_suppress_bare_field_ref(true, NULL, "Field"));
-    ASSERT_FALSE(cbm_go_suppress_bare_field_ref(true, "", "Field"));
-    ASSERT_FALSE(cbm_go_suppress_bare_field_ref(true, "err", NULL));
+    ASSERT_FALSE(cbm_go_suppress_bare_field_ref(false, false, "Field"));
+    /* Degenerate input → nothing to judge. */
+    ASSERT_FALSE(cbm_go_suppress_bare_field_ref(true, false, NULL));
     PASS();
 }