Switch Expression - complete normally - spec omission?

[Manoj Palat]

Thanks Gavin.

Regards
Manoj

-----Gavin Bierman <gavin.bierman at oracle.com> wrote: -----
To: Manoj Palat <manoj.palat at in.ibm.com>
From: Gavin Bierman <gavin.bierman at oracle.com>
Date: 05/21/2020 07:10PM
Cc: amber-spec-experts at openjdk.java.net
Subject: [EXTERNAL] Re: Switch Expression - complete normally - spec omission?

Thanks Manoj. I’ve filed this as a bug [1] and we’ll fix it for JDK 15. 

Cheers,
Gavin

[1] https://bugs.openjdk.java.net/browse/JDK-8245546 

On 16 May 2020, at 10:10, Manoj Palat <manoj.palat at in.ibm.com> wrote:
Thanks Alex for the reply and clarifying that we are discussing Switch Statements with Switch rules.
My bad for putting the title as Switch Expressions - don't want to correct the title now which
will break the chain of the mail.

Regards,
Manoj

-----"amber-spec-experts" <amber-spec-experts-bounces at openjdk.java.net> wrote: -----
To: amber-spec-experts at openjdk.java.net
From: Alex Buckley
Sent by: "amber-spec-experts"
Date: 05/15/2020 11:34PM
Subject: [EXTERNAL] Re: Switch Expression - complete normally - spec omission?

On 5/14/2020 7:22 PM, Manoj Palat wrote:
I think there is a spec omission regarding "complete normally for switch statements whose switch block consists of switch rules

Ref JLS 14 Sec 14.22
...
A switch statement whose switch block consists of switch rules can complete
normally iff at least one of the following is true:
– One of the switch rules introduces a switch rule expression (which is
necessarily a statement expression).
– One of the switch rules introduces a switch rule block that can complete
normally.
– One of the switch rules introduces a switch rule block that contains a reachable
break statement which exits the switch statement.
...
Now consider:

switch (b) {
case 1 -> {
throw new Exception();
}
}

As per the above definition, this switch statement cannot complete normally;
but consider "b" having a value other than 1 and then it completes normally.

/* -----
To demonstrate the point, the switch statement above uses a switch rule
block that completes abruptly, but could alternatively have used a
switch rule `throw` statement:

switch (b) {
  case 1 -> throw new Exception();
}

Also, to clarify for the many readers of this list, we are discussing
switch statements, which never require a `default` label. We are not
discussing switch expressions, which almost always require a `default`
label.
----- */


Also consider, 14.11.3. which says:
"If no switch label matches, the entire switch statement completes normally."

which looks inconsistent. One hand says: "completes normally" the other:
"iff at least one of the following ..." not mentioning default.

Hence, shouldn't the item,
-> – The switch block does not contain a default label.

also be added in the list in 14.22?

I agree that without a `default` switch label, 14.11.3 may evaluate "If
no switch label matches, the entire switch statement completes
normally."  Since we can see a way for the statement to complete
normally, 14.22 ought to say that the statement _can_ complete normally.
So, it looks right to add "– The switch block does not contain a default
label."

Alex