better version, more general intercept (#77)

Author: tomas-villagesql

sql/field.cc

@@ -10491,6 +10491,9 @@ Create_field_wrapper::Create_field_wrapper(const Create_field *fld)
   if (fld->is_unsigned) {
     set_flag(UNSIGNED_FLAG);
   }
+  if (fld->custom_type_context != nullptr) {
+    set_type_context(fld->custom_type_context);
+  }
 }
 
 Item_result Create_field_wrapper::result_type() const {

villagesql/types/util.cc

@@ -1071,38 +1071,7 @@ bool ValidateAndConvertVDFArguments(THD *thd, const char *func_name,
       continue;
     }
 
-    // Case 3: Argument is a column reference (Item_field) without type context
-    // yet. This happens during functional index creation: the table is being
-    // created, so MaybeInjectCustomType hasn't run yet. The field's underlying
-    // Create_field_wrapper (set by replace_field_processor) lets us check
-    // whether the column will actually be a custom type.
-    // We match on qualified_base_name() (extension.type, no parameters),
-    // consistent with Case 1, because VDF signatures cannot express type
-    // parameterization - a VDF declared with param("TVECTOR") must accept any
-    // TVECTOR(N) column.
-    if (args[i]->type() == Item::FIELD_ITEM) {
-      auto *item_field = down_cast<Item_field *>(args[i]);
-      if (item_field->field != nullptr &&
-          item_field->field->is_wrapper_field()) {
-        auto *wrapper =
-            down_cast<const Create_field_wrapper *>(item_field->field);
-        const Create_field *cf = wrapper->get_create_field();
-        if (cf->custom_type_context != nullptr) {
-          if (cf->custom_type_context->qualified_base_name() != expected_qbn) {
-            villagesql_error(
-                "Cannot initialize function '%s': argument %u type mismatch "
-                "(expected %s, got %s)",
-                MYF(0), func_name, i + 1, expected_qbn.c_str(),
-                cf->custom_type_context->qualified_base_name().c_str());
-            return true;
-          }
-          continue;
-        }
-      }
-      // Column has no custom type context - fall through
-    }
-
-    // Case 4: Argument is not a custom type and not a constant string
+    // Case 3: Argument is not a custom type and not a constant string
     villagesql_error(
         "Cannot initialize function '%s': argument %u must be a custom type "
         "or string constant",