Pattern Matching for switch (Second Preview)

[forax at univ-mlv.fr]

----- Original Message -----
> From: "Brian Goetz" <brian.goetz at oracle.com>
> To: "Remi Forax" <forax at univ-mlv.fr>, "Tesla Ice Zhang" <ice1000kotlin at foxmail.com>
> Cc: "jan lahoda" <jan.lahoda at oracle.com>, "amber-dev" <amber-dev at openjdk.java.net>
> Sent: Samedi 25 Septembre 2021 20:10:24
> Subject: Re: Pattern Matching for switch (Second Preview)

>> It's not exactly the same semantics because "Object e" allows null while
>> "default" don't.
> 
> The semantics more more different than that; because default has special
> prvileges with respect to ordering.  Bottom line: don't use default in
> pattern switch, use real patterns.

yes very true,
I would love to have javac to emit a warning if default is not the last case (for all switches).

> 
>>
>>> But I like the default syntax since it can be put to the beginning of the switch
>>> expression, and the type of `e` may not always be Object.
>> You will be able to use "var" instead of "Object" soon.
> 
> Will you ?  News to me.

It's hard to argue that Object o in "case Object o" and case Box(Object o)" should have the same semantics and at the same time allow "case Box(var o)" but do not allow "case var o".

Rémi