Member predicate Parameter :: isDeclaredOptional

Holds if this is a parameter declared optional with the ? token.

Note that this does not hold for rest parameters, and does not in general hold for parameters with defaults.

For example, x, is declared optional below:

function f(x?: number) {}


                            
                                
                                    predicate
                                
                                 
                            
                            
                                isDeclaredOptional
                            
                            
                                (
                                )