description = "True if an error code can be constructed from a `T`."
+++
-True if an error code can be constructed from a `T` e.g. if there exists an ADL discovered free function `make_error_code(T)`.
+`::value` is true if an error code can be constructed from a `T` e.g. if there exists an ADL discovered free function `make_error_code(T)`.
+`::type` is the type that would result if `::value` is true, else `void`.
*Overridable*: By template specialisation into the `trait` namespace.