presto-main/src/main/java/io/prestosql/metadata/FunctionRegistry.java/FunctionRegistry/getUnknownOnlyCastFunctions
class FunctionRegistry:    private List<ApplicableFunction> getUnknownOnlyCastFunctions(List<ApplicableFunction> applicableFunction, List<Type> actualParameters)
    {
        return applicableFunction.stream()
                .filter((function) -> onlyCastsUnknown(function, actualParameters))
                .collect(toImmutableList());
    }