+static inline bool is_type_valid(const type_t *type)
+{
+ assert(!is_typeref(type));
+ return type->kind != TYPE_ERROR;
+}
+
+/**
+ * Allocate a type node of given kind and initialize all
+ * fields with zero.
+ *
+ * @param kind type kind to allocate
+ */
+type_t *allocate_type_zero(type_kind_t kind);
+
+/**
+ * Creates a return_type (func)(void) function type if not
+ * already exists.
+ *
+ * @param return_type the return type
+ */
+type_t *make_function_0_type(type_t *return_type);
+
+/**
+ * Creates a return_type (func)(argument_type) function type if not
+ * already exists.
+ *
+ * @param return_type the return type
+ * @param argument_type the argument type
+ */
+type_t *make_function_1_type(type_t *return_type, type_t *argument_type1);
+
+
+/**
+ * Creates a return_type (func)(argument_type1,argument_type2) function type
+ * if not already exists.
+ */
+type_t *make_function_2_type(type_t *return_type, type_t *argument_type1,
+ type_t *argument_type2);
+
+/**
+ * Creates a return_type (func)(argument_type, ...) function type if not
+ * already exists.
+ *
+ * @param return_type the return type
+ * @param argument_type the argument type
+ */
+type_t *make_function_1_type_variadic(type_t *return_type, type_t *argument_type);
+
+/**
+ * Create a function type with n parameters
+ */
+type_t *make_function_type(type_t *return_type, int n_types,
+ type_t *const *argument_types,
+ decl_modifiers_t modifiers);
+