Function interp_invisible 

fn interp_invisible(
    args: &[RValue],
    _named: &[(String, RValue)],
    context: &BuiltinContext<'_>,
) -> Result<RValue, RError>

Return a value invisibly (suppresses auto-printing).

Sets the interpreter’s visibility flag so that the REPL/eval loop knows not to auto-print the result.

@param x value to return (default: NULL) @return x (invisibly)