Hint user that a POU instance is missing

Is your feature request related to a problem? Please describe. The following code will return a Could not resolve reference to fn_with_one_parameter error

FUNCTION_BLOCK fn_with_one_parameter
    VAR_INPUT
        in_one : DINT;
    END_VAR
END_FUNCTION_BLOCK

FUNCTION main : DINT
    fn_with_one_parameter(1);
END_FUNCTION

This is because an instance hasn't been declared. Knowing this is a FUNCTION_BLOCK it would be nice to hint the user that they're not dealing with functions and are missing an instance declaration.

Describe the solution you'd like Improve the error message