The program contains a predefinition of a function, but not its actual definition.

#2509   Compile-time warning

The program contains a predefinition of a function, but not its actual definition.

Additional Information

The function 'X' was first predefined on line N of file 'F'.
    or
The conversion function was first predefined on line N of file 'F'.
    in case the function was predefined with define conversion-function.

Recovery

Compilation continues normally.

Explanation

A function has been predefined using elsewhere syntax, but its actual definition is missing. This message is only a warning because the function is never called.