I was reading D language reference and found some issue with "case ... :" statement specifications.
Documentation http://dlang.org/statement#CaseStatement  says that after

case 1:

must be non-empty statement "ScopeStatementList". For example

case 1:

}
case 2: ;
case 3

Sorry for previous message. Once again:

I was reading D language reference and found some issue with
"case ... :" statement specifications.
Documentation http://dlang.org/statement#CaseStatement  says
that after

case 1:

must be non-empty statement "ScopeStatementList". For example

case 1:
  return true;

case 2: {
}

case 3: ;

But next example concerns me:

case 1:
case 2:
  return true;
case 3:
  return false;

After "case 1:" we see no statement at all. This conflicts with "CaseStatement" rule of documentation. But this is right D code.
I think language reference must be updated.

"Sergey Kozyr"  wrote in message news:khaugqemvygmsaaeyild@forum.dlang.org...

> case 1:
> case 2:
>    return true;
> case 3:
>    return false;
>
> After "case 1:" we see no statement at all. This conflicts with "CaseStatement" rule of documentation. But this is right D code.
> I think language reference must be updated.

"case 2:" is a CaseStatement and it's after "case 1:" 

On Thursday, 14 August 2014 at 13:19:36 UTC, Sergey Kozyr wrote:
> Sorry for previous message. Once again:
>
> I was reading D language reference and found some issue with
> "case ... :" statement specifications.
> Documentation http://dlang.org/statement#CaseStatement  says
> that after
>
> case 1:
>
> must be non-empty statement "ScopeStatementList". For example
>
> case 1:
>   return true;
>
> case 2: {
> }
>
> case 3: ;
>
> But next example concerns me:
>
> case 1:
> case 2:
>   return true;
> case 3:
>   return false;
>
> After "case 1:" we see no statement at all. This conflicts with "CaseStatement" rule of documentation. But this is right D code.
> I think language reference must be updated.

It's a "fall trough":

https://en.wikipedia.org/wiki/Switch_statement#Fallthrough

On Thursday, 14 August 2014 at 16:01:05 UTC, Baz wrote:
> On Thursday, 14 August 2014 at 13:19:36 UTC, Sergey Kozyr wrote:
>> Sorry for previous message. Once again:
>>
>> I was reading D language reference and found some issue with
>> "case ... :" statement specifications.
>> Documentation http://dlang.org/statement#CaseStatement  says
>> that after
>>
>> case 1:
>>
>> must be non-empty statement "ScopeStatementList". For example
>>
>> case 1:
>>  return true;
>>
>> case 2: {
>> }
>>
>> case 3: ;
>>
>> But next example concerns me:
>>
>> case 1:
>> case 2:
>>  return true;
>> case 3:
>>  return false;
>>
>> After "case 1:" we see no statement at all. This conflicts with "CaseStatement" rule of documentation. But this is right D code.
>> I think language reference must be updated.
>
> It's a "fall trough":
>
> https://en.wikipedia.org/wiki/Switch_statement#Fallthrough

It's a fall trough but it is not the reason why it does works. It does because (as Daniel already mentioned) a case is a valid statement, therefore a case following other case is a totally valid statement.

for example:

case 1:
case 2:
  return true;

There are three statements. One which must be followed by another (case keyword) and another by an expression (return keyword).

It is not even a special-case in the switch in C language. The switch keyword accept a expression constant as argument and must be followed by a statement, so:

switch(1) return 0;

is valid C code and no standard-compliant compiler must give an error about that. The fact we can do:

switch(E)
{
   case 1: ... break;
   case 2: .... break;
default: ... break;
}

That's why compound-statement is a statement too (which switch does accept same reason why break keyword is needed)

On Thursday, 14 August 2014 at 17:10:50 UTC, AsmMan wrote:
> On Thursday, 14 August 2014 at 16:01:05 UTC, Baz wrote:
>> On Thursday, 14 August 2014 at 13:19:36 UTC, Sergey Kozyr wrote:
>>> Sorry for previous message. Once again:
>>>
>>> I was reading D language reference and found some issue with
>>> "case ... :" statement specifications.
>>> Documentation http://dlang.org/statement#CaseStatement  says
>>> that after
>>>
>>> case 1:
>>>
>>> must be non-empty statement "ScopeStatementList". For example
>>>
>>> case 1:
>>> return true;
>>>
>>> case 2: {
>>> }
>>>
>>> case 3: ;
>>>
>>> But next example concerns me:
>>>
>>> case 1:
>>> case 2:
>>> return true;
>>> case 3:
>>> return false;
>>>
>>> After "case 1:" we see no statement at all. This conflicts with "CaseStatement" rule of documentation. But this is right D code.
>>> I think language reference must be updated.
>>
>> It's a "fall trough":
>>
>> https://en.wikipedia.org/wiki/Switch_statement#Fallthrough
>
> It's a fall trough but it is not the reason why it does works. It does because (as Daniel already mentioned) a case is a valid statement, therefore a case following other case is a totally valid statement.
>
> for example:
>
> case 1:
> case 2:
>   return true;
>
> There are three statements. One which must be followed by another (case keyword) and another by an expression (return keyword).
>
> It is not even a special-case in the switch in C language. The switch keyword accept a expression constant as argument and must be followed by a statement, so:
>
> switch(1) return 0;
>
> is valid C code and no standard-compliant compiler must give an error about that. The fact we can do:
>
> switch(E)
> {
>    case 1: ... break;
>    case 2: .... break;
> default: ... break;
> }
>
> That's why compound-statement is a statement too (which switch does accept same reason why break keyword is needed)

I totally agree. I just wanted to mention the technical name.

> It's a fall trough but it is not the reason why it does works. It does because (as Daniel already mentioned) a case is a valid statement, therefore a case following other case is a totally valid statement.
>
> for example:
>
> case 1:
> case 2:
>   return true;
>
> There are three statements. One which must be followed by another (case keyword) and another by an expression (return keyword).


I agree that this is a valid D language construction. But documentation says that statement "case 1:" must be followed by any statement except other "case" or "default".
Let's open doc http://dlang.org/statement#CaseStatement
You see that "case ArgumentList :" is followed by "ScopeStatementList" (http://dlang.org/statement#ScopeStatementList) which is a list of any statements except CaseStatement or CaseRangeStatement or DefaultStatement. This rule conflicts with actual D language compiler.

On Fri, 15 Aug 2014 19:46:07 +0000
Sergey Kozyr via Digitalmars-d <digitalmars-d@puremagic.com> wrote:

> Let's open doc http://dlang.org/statement#CaseStatement
and we'll find some more bugs there:

  CaseStatement:
    case ArgumentList : ScopeStatementList

  ArgumentList:
    AssignExpression
    AssignExpression ,
    AssignExpression , ArgumentList

  AssignExpression:
    ConditionalExpression
    ConditionalExpression = AssignExpression
    ConditionalExpression += AssignExpression
    ...

and so on.

so we can see that things like 'case n+=5:' should be allowed, while they are not.

On 08/16/2014 12:21 AM, ketmar via Digitalmars-d wrote:
> so we can see that things like 'case n+=5:' should be allowed, while
> they are not.

What is the problem? This passes DMD's parser.

On Sat, 16 Aug 2014 01:31:42 +0200
Timon Gehr via Digitalmars-d <digitalmars-d@puremagic.com> wrote:

> What is the problem? This passes DMD's parser.
that is the problem: it shouldn't. this has no sense, and it's easy to fix this in grammar itself.