Encountered a duplicate function parameter.
#2021 Compile-time error
Encountered a duplicate function parameter.
Additional Information
In function 'X', for parameter Y 'Z'.
or
In function 'X', parameter 'Y' was already declared as type 'Z'.
Recovery
Compilation continues but no compiled source code file will be saved.
Explanation
Each parameter identifier (the shelf type and its name) may appear
only once in the parameter list for a given function.