fix(graph): precise Struct label for Rust/Swift/D/Go structs (Option B)

Struct definitions were labelled 'Class', conflating a distinct kind. Emit
the precise 'Struct' label for Rust (struct_item), Swift/D (struct_declaration)
and Go (type_spec struct_type); C/C++/Obj-C struct_specifier stays 'Class'.

To avoid regressing type resolution, a struct must still behave as a type
everywhere a class does. Added a centralized predicate cbm_label_is_type_like()
(Class/Struct/Interface/Enum/Type/Trait) and routed every type-like consumer
through it: registry seeding (pass_definitions/pass_parallel/pipeline_incremental
kept in sync), class-resolution (pass_semantic/pass_parallel resolve_as_class),
Go interface satisfaction (collects Struct nodes), the cross-file LSP label map,
and the Go/Rust LSP type registrars. Class-only sites (protobuf services, K8s
kinds, the C-family LSPs) are left unchanged.

Signed-off-by: Martin Vogel <martin.vogel.tech@gmail.com>

internal/cbm/cbm.h

@@ -598,4 +598,17 @@ void cbm_extract_unified(CBMExtractCtx *ctx);
 // K8s / Kustomize semantic extractor (called when language is CBM_LANG_K8S or CBM_LANG_KUSTOMIZE).
 void cbm_extract_k8s(CBMExtractCtx *ctx);
 
+// --- Label predicates ---
+
+// True when `label` names a TYPE-LIKE container definition — a node that can own
+// methods/fields, be a base/embedded type, satisfy/declare an interface, and be a
+// target of name→type resolution. The canonical set is:
+//   Class, Struct, Interface, Enum, Type, Trait.
+// Single source of truth for every type-resolution / registry-seeding /
+// INHERITS·IMPLEMENTS / LSP-type-registrar consumer, so adding a new type-like
+// label (e.g. "Struct" for Rust/Go/Swift/D structs) updates them all at once
+// instead of scattering `|| strcmp(label,"Struct")==0` across the tree.
+// `label` may be NULL (returns false). Defined in helpers.c.
+bool cbm_label_is_type_like(const char *label);
+
 #endif // CBM_H

internal/cbm/extract_defs.c

@@ -3502,8 +3502,8 @@ static void extract_class_def(CBMExtractCtx *ctx, TSNode node, const CBMLangSpec
 
     // Sway/WGSL: label struct defs as "Struct" and Sway `abi` blocks as
     // "Interface". Scoped to these grammar-only languages so established
-    // struct-as-"Class" labeling (Rust/C++/Go/Cap'n Proto …) and the
-    // downstream type/IMPLEMENTS resolvers that depend on it are unaffected.
+    // struct-as-"Class" labeling (C++/Cap'n Proto …) and the downstream
+    // type/IMPLEMENTS resolvers that depend on it are unaffected.
     if (ctx->language == CBM_LANG_SWAY || ctx->language == CBM_LANG_WGSL) {
         if (strcmp(kind, "struct_item") == 0 || strcmp(kind, "struct_declaration") == 0) {
             label = "Struct";
@@ -3511,6 +3511,20 @@ static void extract_class_def(CBMExtractCtx *ctx, TSNode node, const CBMLangSpec
             label = "Interface";
         }
     }
+    // Rust/Swift/D: a struct is a distinct kind from a class — emit the precise
+    // "Struct" label rather than collapsing it to "Class". Scoped to these three
+    // grammar/LSP languages whose struct node is `struct_item` (Rust) or
+    // `struct_declaration` (Swift, D). C/C++/Obj-C keep `struct_specifier` →
+    // "Class" (a C++ struct is class-like). "Struct" is a type-like container:
+    // every type-resolution / registry / IMPLEMENTS / LSP-registrar consumer
+    // routes through cbm_label_is_type_like(), so a struct still resolves as a
+    // type for its methods, fields, inheritance and impls.
+    if (ctx->language == CBM_LANG_RUST || ctx->language == CBM_LANG_SWIFT ||
+        ctx->language == CBM_LANG_DLANG) {
+        if (strcmp(kind, "struct_item") == 0 || strcmp(kind, "struct_declaration") == 0) {
+            label = "Struct";
+        }
+    }
     // F#: a `type_definition` that has a primary constructor (`type Foo(...) =`)
     // or an `inherit` clause is an OOP class, not a plain type alias. Label it
     // "Class" so it is registered as a resolvable inheritance target (the graph
@@ -3525,7 +3539,10 @@ static void extract_class_def(CBMExtractCtx *ctx, TSNode node, const CBMLangSpec
         }
     }
 
-    // Go type_spec: check inner type for interface/struct
+    // Go type_spec: check inner type for interface/struct. A Go `type T struct
+    // {...}` is a struct → emit the precise "Struct" label (a type-like container;
+    // its methods/fields/embedding resolve through cbm_label_is_type_like(), and
+    // cbm_pipeline_implements_go() collects Struct nodes too).
     if (strcmp(kind, "type_spec") == 0) {
         TSNode type_inner = ts_node_child_by_field_name(node, TS_FIELD("type"));
         if (!ts_node_is_null(type_inner)) {
@@ -3533,7 +3550,7 @@ static void extract_class_def(CBMExtractCtx *ctx, TSNode node, const CBMLangSpec
             if (strcmp(inner_kind, "interface_type") == 0) {
                 label = "Interface";
             } else if (strcmp(inner_kind, "struct_type") == 0) {
-                label = "Class";
+                label = "Struct";
             }
         }
     }

internal/cbm/helpers.c

@@ -155,6 +155,18 @@ static const char *puppet_keywords[] = {
     "and",    "or",    "in",     "node",  "class", "define", "inherits", "default",
     "return", NULL};
 
+// True when `label` names a type-like container definition (see cbm.h). Single
+// source of truth for the type-resolution / registry / IMPLEMENTS / LSP-type
+// consumers — adding a label here updates them all.
+bool cbm_label_is_type_like(const char *label) {
+    if (!label) {
+        return false;
+    }
+    return strcmp(label, "Class") == 0 || strcmp(label, "Struct") == 0 ||
+           strcmp(label, "Interface") == 0 || strcmp(label, "Enum") == 0 ||
+           strcmp(label, "Type") == 0 || strcmp(label, "Trait") == 0;
+}
+
 bool cbm_is_keyword(const char *name, CBMLanguage lang) {
     if (!name || !name[0]) {
         return true;

internal/cbm/lsp/go_lsp.c

@@ -1713,9 +1713,10 @@ void cbm_run_go_lsp(CBMArena* arena, CBMFileResult* result,
         CBMDefinition* d = &result->defs.items[i];
         if (!d->qualified_name || !d->name) continue;
 
-        // Register Class/Type nodes
-        if (d->label && (strcmp(d->label, "Class") == 0 || strcmp(d->label, "Type") == 0 ||
-                         strcmp(d->label, "Interface") == 0)) {
+        // Register every type-like container (Class/Struct/Type/Interface/Enum/
+        // Trait). Struct included so a Go `type T struct {...}` (now labelled
+        // "Struct") is registered as a type and its methods/embedding resolve.
+        if (cbm_label_is_type_like(d->label)) {
             CBMRegisteredType rt;
             memset(&rt, 0, sizeof(rt));
             rt.qualified_name = d->qualified_name;
@@ -2534,9 +2535,9 @@ void cbm_run_go_lsp_cross(
 
         const char* def_mod = d->def_module_qn ? d->def_module_qn : module_qn;
 
-        // Type/Interface/Class
-        if (strcmp(d->label, "Type") == 0 || strcmp(d->label, "Class") == 0 ||
-            strcmp(d->label, "Interface") == 0) {
+        // Every type-like container (Type/Class/Struct/Interface/Enum/Trait).
+        // Struct included so Go structs (now labelled "Struct") register as types.
+        if (cbm_label_is_type_like(d->label)) {
             CBMRegisteredType rt;
             memset(&rt, 0, sizeof(rt));
             rt.qualified_name = d->qualified_name;  // borrowed
@@ -2787,8 +2788,9 @@ CBMTypeRegistry* cbm_go_build_cross_registry(
          * fall back to — this registry is project-wide, not per-file. */
         const char* def_mod = d->def_module_qn ? d->def_module_qn : "";
 
-        if (strcmp(d->label, "Type") == 0 || strcmp(d->label, "Class") == 0 ||
-            strcmp(d->label, "Interface") == 0) {
+        // Every type-like container (Type/Class/Struct/Interface/Enum/Trait).
+        // Struct included so Go structs (now labelled "Struct") register as types.
+        if (cbm_label_is_type_like(d->label)) {
             CBMRegisteredType rt;
             memset(&rt, 0, sizeof(rt));
             rt.qualified_name = d->qualified_name; /* borrowed */

internal/cbm/lsp/rust_lsp.c

@@ -4530,8 +4530,10 @@ static void rust_build_registry_from_defs(CBMArena *arena, CBMTypeRegistry *reg,
         if (!d->qualified_name || !d->name)
             continue;
 
-        if (d->label && (strcmp(d->label, "Class") == 0 || strcmp(d->label, "Type") == 0 ||
-                         strcmp(d->label, "Interface") == 0 || strcmp(d->label, "Trait") == 0)) {
+        // Every type-like container (Class/Struct/Type/Interface/Trait/Enum).
+        // Struct included so a Rust `struct Foo` (now labelled "Struct") registers
+        // as a type and its `impl Foo` methods/fields resolve.
+        if (cbm_label_is_type_like(d->label)) {
             CBMRegisteredType rt;
             memset(&rt, 0, sizeof(rt));
             rt.qualified_name = d->qualified_name;
@@ -4839,7 +4841,10 @@ static void rust_build_registry_from_defs(CBMArena *arena, CBMTypeRegistry *reg,
             CBMDefinition *d = &result->defs.items[i];
             if (!d->qualified_name || !d->name)
                 continue;
-            if (!d->label || (strcmp(d->label, "Class") != 0 && strcmp(d->label, "Type") != 0))
+            /* `#[derive(...)]` rides on type-like defs — most often a struct or
+             * enum (now labelled "Struct"/"Enum"), also type aliases. Accept the
+             * whole type-like set so a derive on a struct is not dropped. */
+            if (!cbm_label_is_type_like(d->label))
                 continue;
             if (!d->decorators)
                 continue;
@@ -5151,8 +5156,9 @@ void cbm_run_rust_lsp_cross(CBMArena *arena, const char *source, int source_len,
             continue;
         const char *def_mod = d->def_module_qn ? d->def_module_qn : module_qn;
 
-        if (strcmp(d->label, "Type") == 0 || strcmp(d->label, "Class") == 0 ||
-            strcmp(d->label, "Interface") == 0 || strcmp(d->label, "Trait") == 0) {
+        // Every type-like container (Type/Class/Struct/Interface/Trait/Enum).
+        // Struct included so Rust structs (now labelled "Struct") register here.
+        if (cbm_label_is_type_like(d->label)) {
             CBMRegisteredType rt;
             memset(&rt, 0, sizeof(rt));
             rt.qualified_name = cbm_arena_strdup(arena, d->qualified_name);

src/pipeline/pass_configlink.c

@@ -105,7 +105,7 @@ static int collect_config_entries(const cbm_gbuf_node_t *const *vars, int var_co
     return n;
 }
 
-/* Collect code nodes (Function/Variable/Class) not from config files. */
+/* Collect code nodes (Function/Variable/Class/Struct) not from config files. */
 typedef struct {
     int64_t node_id;
     char normalized[CBM_SZ_256];
@@ -113,7 +113,9 @@ typedef struct {
 
 static int collect_code_entries(cbm_gbuf_t *gb, code_entry_t *out, int max_out) {
     int n = 0;
-    static const char *labels[] = {"Function", "Variable", "Class", NULL};
+    /* "Struct" alongside "Class": a config key may name a Go/Rust/Swift/D struct
+     * type, which is now labelled "Struct" — keep it linkable. */
+    static const char *labels[] = {"Function", "Variable", "Class", "Struct", NULL};
 
     for (int li = 0; labels[li] && n < max_out; li++) {
         const cbm_gbuf_node_t **nodes = NULL;

src/pipeline/pass_definitions.c

@@ -295,15 +295,18 @@ static void process_def(cbm_pipeline_ctx_t *ctx, const CBMDefinition *def, const
     int64_t node_id = cbm_gbuf_upsert_node(
         ctx->gbuf, def->label ? def->label : "Function", def->name, def->qualified_name,
         def->file_path ? def->file_path : rel, (int)def->start_line, (int)def->end_line, props);
-    /* Register callable symbols + Interface.  Interface must be in the registry
-     * so C#/Java `class Foo : IBar` / `class Foo implements IBar` can resolve
-     * `IBar` to an INHERITS edge target during the enrichment phase.
-     * Variable/Field defs are also registered so pass_usages.c can resolve
-     * READS/WRITES accesses (rw->var_name) to a Variable/Field node QN. */
+    /* Register callable symbols + every type-like container (Class/Struct/
+     * Interface/Enum/Type/Trait). Type-like defs must be in the registry so
+     * `class Foo : IBar` (INHERITS), `impl Trait for S` (IMPLEMENTS), and method/
+     * field resolution can reach them — Struct included so Rust/Go/Swift/D structs
+     * resolve as type targets just as a Class did. Variable/Field defs are also
+     * registered so pass_usages.c can resolve READS/WRITES accesses (rw->var_name)
+     * to a Variable/Field node QN.
+     * KEEP IN SYNC with pass_parallel.c and pipeline_incremental.c's seed sets. */
     if (node_id > 0 && def->label &&
         (strcmp(def->label, "Function") == 0 || strcmp(def->label, "Method") == 0 ||
-         strcmp(def->label, "Class") == 0 || strcmp(def->label, "Interface") == 0 ||
-         strcmp(def->label, "Variable") == 0 || strcmp(def->label, "Field") == 0)) {
+         cbm_label_is_type_like(def->label) || strcmp(def->label, "Variable") == 0 ||
+         strcmp(def->label, "Field") == 0)) {
         cbm_registry_add(ctx->registry, def->name, def->qualified_name, def->label);
     }
     char *file_qn = cbm_pipeline_fqn_compute(ctx->project_name, rel, "__file__");

src/pipeline/pass_enrichment.c

@@ -292,8 +292,11 @@ static void free_tagged_nodes(tagged_node_t *nodes, int count) {
 /* Phase 1: Collect decorated nodes and count word frequency. */
 static int collect_decorated_nodes(cbm_gbuf_t *gbuf, tagged_node_t **out_nodes,
                                    CBMHashTable *word_counts) {
-    static const char *labels[] = {"Function", "Method", "Class"};
-    static const int nlabels = 3;
+    /* "Struct" alongside "Class" so Go/Rust/Swift/D struct names keep
+     * contributing to / receiving auto-tags as they did when structs were
+     * labelled "Class". */
+    static const char *labels[] = {"Function", "Method", "Class", "Struct"};
+    static const int nlabels = 4;
     tagged_node_t *nodes = NULL;
     int node_count = 0;
     int node_cap = 0;

src/pipeline/pass_lsp_cross.c

@@ -82,16 +82,16 @@ static char *pxc_read_file(const char *path, int *out_len) {
     return buf;
 }
 
-/* Map a CBMDefinition.label to a CBMLSPDef.label. Per-language LSP
- * registrars only care about Class/Interface/Trait/Enum/Type/Protocol/
- * Function/Method — variables, modules, decorators, etc. are skipped. */
+/* Map a CBMDefinition.label to a CBMLSPDef.label. Per-language LSP registrars
+ * only care about type-like containers (Class/Struct/Interface/Trait/Enum/Type)
+ * plus Protocol/Function/Method — variables, modules, decorators, etc. are
+ * skipped. Struct passes through so Rust/Go struct type-registration via the
+ * cross-file LSP path is not dropped. */
 static const char *pxc_map_label(const char *label) {
     if (!label)
         return NULL;
-    if (strcmp(label, "Class") == 0 || strcmp(label, "Interface") == 0 ||
-        strcmp(label, "Trait") == 0 || strcmp(label, "Enum") == 0 || strcmp(label, "Type") == 0 ||
-        strcmp(label, "Protocol") == 0 || strcmp(label, "Function") == 0 ||
-        strcmp(label, "Method") == 0) {
+    if (cbm_label_is_type_like(label) || strcmp(label, "Protocol") == 0 ||
+        strcmp(label, "Function") == 0 || strcmp(label, "Method") == 0) {
         return label;
     }
     return NULL;

src/pipeline/pass_parallel.c

@@ -410,12 +410,12 @@ static const char *resolve_as_class(const cbm_registry_t *reg, const char *name,
     if (!res.qualified_name || res.qualified_name[0] == '\0') {
         return NULL;
     }
+    /* Accept any type-like container (Class/Struct/Interface/Enum/Type/Trait):
+     * base classes, Rust `impl Trait for S` struct receivers, and Go struct
+     * embedding all resolve through here. Struct included so the struct receiver
+     * of an IMPLEMENTS edge is not dropped. */
     const char *label = cbm_registry_label_of(reg, res.qualified_name);
-    if (!label) {
-        return NULL;
-    }
-    if (strcmp(label, "Class") != 0 && strcmp(label, "Interface") != 0 &&
-        strcmp(label, "Type") != 0 && strcmp(label, "Enum") != 0) {
+    if (!cbm_label_is_type_like(label)) {
         return NULL;
     }
     return res.qualified_name;
@@ -822,11 +822,14 @@ static int register_and_link_def(cbm_pipeline_ctx_t *ctx, const CBMDefinition *d
     if (!def->name || !def->qualified_name || !def->label) {
         return 0;
     }
-    /* Register callable symbols + Interface — see pass_definitions.c for rationale.
-     * Variable/Field defs are registered too so READS/WRITES can resolve. */
+    /* Register callable symbols + every type-like container (Class/Struct/
+     * Interface/Enum/Type/Trait) — see pass_definitions.c for rationale. Struct
+     * included so Rust/Go/Swift/D structs resolve as type targets. Variable/Field
+     * defs are registered too so READS/WRITES can resolve.
+     * KEEP IN SYNC with pass_definitions.c and pipeline_incremental.c. */
     if (strcmp(def->label, "Function") == 0 || strcmp(def->label, "Method") == 0 ||
-        strcmp(def->label, "Class") == 0 || strcmp(def->label, "Interface") == 0 ||
-        strcmp(def->label, "Variable") == 0 || strcmp(def->label, "Field") == 0) {
+        cbm_label_is_type_like(def->label) || strcmp(def->label, "Variable") == 0 ||
+        strcmp(def->label, "Field") == 0) {
         cbm_registry_add(ctx->registry, def->name, def->qualified_name, def->label);
         (*reg_entries)++;
     }

src/pipeline/pass_semantic.c

@@ -167,13 +167,12 @@ static const char *resolve_as_class(const cbm_registry_t *reg, const char *name,
         return NULL;
     }
 
-    /* Verify it's a Class, Interface, or Type */
+    /* Verify it's a type-like container (Class/Struct/Interface/Enum/Type/Trait):
+     * a base/embedded type, impl receiver, or inheritance target must resolve to
+     * one of these. Struct included so Rust/Go/Swift/D `impl Trait for S` and Go
+     * struct embedding resolve. */
     const char *label = cbm_registry_label_of(reg, res.qualified_name);
-    if (!label) {
-        return NULL;
-    }
-    if (strcmp(label, "Class") != 0 && strcmp(label, "Interface") != 0 &&
-        strcmp(label, "Type") != 0 && strcmp(label, "Enum") != 0) {
+    if (!cbm_label_is_type_like(label)) {
         return NULL;
     }
     return res.qualified_name;
@@ -301,11 +300,16 @@ int cbm_pipeline_implements_go(cbm_pipeline_ctx_t *ctx) {
         return 0;
     }
 
-    /* Find all Class nodes */
+    /* Find candidate concrete types. In Go the type that satisfies an interface
+     * is a struct (now labelled "Struct") or a named type (labelled "Class"); both
+     * sets are checked. Each call returns a borrowed internal array (no free). */
     const cbm_gbuf_node_t **classes = NULL;
     int class_count = 0;
     cbm_gbuf_find_by_label(ctx->gbuf, "Class", &classes, &class_count);
-    if (class_count == 0) {
+    const cbm_gbuf_node_t **structs = NULL;
+    int struct_count = 0;
+    cbm_gbuf_find_by_label(ctx->gbuf, "Struct", &structs, &struct_count);
+    if (class_count == 0 && struct_count == 0) {
         return 0;
     }
 
@@ -337,7 +341,11 @@ int cbm_pipeline_implements_go(cbm_pipeline_ctx_t *ctx) {
             continue;
         }
 
-        /* Check each Class node for method-set satisfaction */
+        /* Check each concrete-type node (Struct + Class) for method-set
+         * satisfaction. */
+        for (int c = 0; c < struct_count; c++) {
+            edge_count += check_go_class_implements(ctx, structs[c], iface, imethods, im_count);
+        }
         for (int c = 0; c < class_count; c++) {
             edge_count += check_go_class_implements(ctx, classes[c], iface, imethods, im_count);
         }

src/pipeline/pipeline_incremental.c

@@ -509,9 +509,13 @@ static void persist_hashes(cbm_store_t *store, const char *project, cbm_file_inf
  * resolve to the same-named Module node instead of the Class node. Only
  * callable / declared symbols belong in the registry. */
 static bool incr_label_is_registry_symbol(const char *label) {
+    /* Mirror pass_definitions.c / pass_parallel.c registry seeding EXACTLY:
+     * callables + every type-like container (Class/Struct/Interface/Enum/Type/
+     * Trait) + Variable/Field. Struct included so an incremental re-resolve seeds
+     * the same struct type nodes a full reindex would. */
     return label && (strcmp(label, "Function") == 0 || strcmp(label, "Method") == 0 ||
-                     strcmp(label, "Class") == 0 || strcmp(label, "Interface") == 0 ||
-                     strcmp(label, "Variable") == 0 || strcmp(label, "Field") == 0);
+                     cbm_label_is_type_like(label) || strcmp(label, "Variable") == 0 ||
+                     strcmp(label, "Field") == 0);
 }
 
 /* Callback for cbm_gbuf_foreach_node: seed the registry with the existing

src/ui/layout3d.c

@@ -85,6 +85,8 @@ static float size_for_label(const char *label) {
         return 8.0f;
     if (strcmp(label, "Class") == 0)
         return 6.0f;
+    if (strcmp(label, "Struct") == 0)
+        return 6.0f;
     if (strcmp(label, "Interface") == 0)
         return 6.0f;
     if (strcmp(label, "Function") == 0)