Begin to fix some `let` instruction

src/language/ASTNodeDataTypeBuilder.cpp

@@ -82,13 +82,18 @@ ASTNodeDataTypeBuilder::_buildNodeDataTypes(ASTNode& n)
           i_symbol->attributes().setDataType(n.children[0]->m_data_type);
         }
 
-        if (parameters_domain_node.children.size() != parameters_name_node.children.size()) {
+        const size_t nb_parameter_domains =
+          (parameters_domain_node.children.size() > 0) ? parameters_domain_node.children.size() : 1;
+        const size_t nb_parameter_names =
+          (parameters_name_node.children.size() > 0) ? parameters_name_node.children.size() : 1;
+
+        if (nb_parameter_domains != nb_parameter_names) {
           std::ostringstream message;
           message << "Compound data type deduction is not yet implemented\n"
-                  << "note: number of product spaces (" << parameters_domain_node.children.size() << ") "
-                  << rang::fgB::yellow << parameters_domain_node.string() << rang::style::reset
-                  << " differs  from number of variables (" << parameters_name_node.children.size() << ") "
-                  << rang::fgB::yellow << parameters_name_node.string() << rang::style::reset << std::ends;
+                  << "note: number of product spaces (" << nb_parameter_domains << ") " << rang::fgB::yellow
+                  << parameters_domain_node.string() << rang::style::reset << rang::style::bold
+                  << " differs from number of variables (" << nb_parameter_names << ") " << rang::fgB::yellow
+                  << parameters_name_node.string() << rang::style::reset << std::ends;
           throw parse_error(message.str(), n.children[0]->begin());
         }
 
@@ -117,7 +122,7 @@ ASTNodeDataTypeBuilder::_buildNodeDataTypes(ASTNode& n)
           Assert(found);
           i_symbol->attributes().setDataType(data_type);
         };
-
+#warning This test is probably incorrect
         if (parameters_domain_node.children.size() == 0) {
           simple_type_allocator(parameters_domain_node, parameters_name_node);
         } else {