fix(csharp): preserve escaped constructors and conditional extension members

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

internal/cbm/extract_defs.c

@@ -8943,9 +8943,15 @@ static bool csharp_is_extension_block(TSNode node, TSNode class_node, const char
     }
     TSNode type_name = ts_node_child_by_field_name(class_node, TS_FIELD("name"));
     if (!ts_node_is_null(type_name)) {
+        const char *type_text = source + ts_node_start_byte(type_name);
         uint32_t tlen = ts_node_end_byte(type_name) - ts_node_start_byte(type_name);
-        if (tlen == kw_len &&
-            strncmp(source + ts_node_start_byte(type_name), "extension", kw_len) == 0) {
+        /* A verbatim identifier names the same type: class @extension may
+         * declare a genuine constructor spelled extension(). */
+        if (tlen > 0 && type_text[0] == '@') {
+            type_text++;
+            tlen--;
+        }
+        if (tlen == kw_len && strncmp(type_text, "extension", kw_len) == 0) {
             return false;
         }
     }
@@ -8963,11 +8969,11 @@ static void extract_csharp_extension_members(CBMExtractCtx *ctx, TSNode ext_node
     if (ts_node_is_null(body)) {
         return;
     }
-    uint32_t count = ts_node_child_count(body);
-    for (uint32_t i = 0; i < count; i++) {
-        TSNode member = ts_node_child(body, i);
-        if (ts_node_is_null(member) ||
-            strcmp(ts_node_type(member), "local_function_statement") != 0) {
+    member_iter_t it;
+    member_iter_init(&it, body, ctx->language, false);
+    TSNode member;
+    while (member_iter_next(&it, &member)) {
+        if (strcmp(ts_node_type(member), "local_function_statement") != 0) {
             continue;
         }
         TSNode name = resolve_method_name(member, ctx->language);
@@ -8976,6 +8982,7 @@ static void extract_csharp_extension_members(CBMExtractCtx *ctx, TSNode ext_node
         }
         push_method_def(ctx, member, class_node, class_qn, spec, name);
     }
+    member_iter_done(&it);
 }
 
 // Extract methods inside a class body

tests/test_extraction.c

@@ -916,6 +916,52 @@ TEST(csharp_constructor_of_type_named_extension) {
     PASS();
 }
 
+/* Escaping a type identifier does not change its constructor's identity. */
+TEST(csharp_constructor_of_escaped_type_named_extension) {
+    const char *src = "namespace App { public class @extension { "
+                      "public extension() { int ConstructorLocal() => 1; } } }";
+    CBMFileResult *r = extract(src, CBM_LANG_CSHARP, "t", "extension.cs");
+    ASSERT_NOT_NULL(r);
+    ASSERT_FALSE(r->has_error);
+    ASSERT(has_def(r, "Method", "extension"));
+    ASSERT_FALSE(has_def(r, "Method", "ConstructorLocal"));
+    cbm_free_result(r);
+    PASS();
+}
+
+/* All conditional branches expose extension members, but method-local
+ * functions must never be promoted to members of the enclosing type. */
+TEST(csharp_extension_block_conditional_members) {
+    const char *src = "public static class TextExtensions\n"
+                      "{\n"
+                      "    extension(string text)\n"
+                      "    {\n"
+                      "#if FIRST\n"
+                      "        public int First() { int Nested() => 1; return Nested(); }\n"
+                      "#elif SECOND\n"
+                      "        public int Second() => 2;\n"
+                      "#else\n"
+                      "#if NESTED\n"
+                      "        public int Third() => 3;\n"
+                      "#else\n"
+                      "        public int Fourth() => 4;\n"
+                      "#endif\n"
+                      "#endif\n"
+                      "    }\n"
+                      "}\n";
+    CBMFileResult *r = extract(src, CBM_LANG_CSHARP, "t", "TextExtensions.cs");
+    ASSERT_NOT_NULL(r);
+    ASSERT_FALSE(r->has_error);
+    ASSERT(has_def(r, "Method", "First"));
+    ASSERT(has_def(r, "Method", "Second"));
+    ASSERT(has_def(r, "Method", "Third"));
+    ASSERT(has_def(r, "Method", "Fourth"));
+    ASSERT_FALSE(has_def_any(r, "extension"));
+    ASSERT_FALSE(has_def(r, "Method", "Nested"));
+    cbm_free_result(r);
+    PASS();
+}
+
 /* --- Swift --- */
 TEST(swift_class) {
     CBMFileResult *r = extract("class Vehicle {\n    var speed: Int = 0\n    func accelerate() { "
@@ -13195,6 +13241,8 @@ SUITE(extraction) {
     RUN_TEST(csharp_interface);
     RUN_TEST(csharp_extension_block_members);
     RUN_TEST(csharp_constructor_of_type_named_extension);
+    RUN_TEST(csharp_constructor_of_escaped_type_named_extension);
+    RUN_TEST(csharp_extension_block_conditional_members);
     RUN_TEST(swift_class);
     RUN_TEST(swift_protocol);
     RUN_TEST(kotlin_function);