labeled block stement.

[Nick Treleaven]

On 20/12/2012 12:00, monarch_dodra wrote:
> I had (some time ago), created a request for breakable labeled blocks:
> http://d.puremagic.com/issues/show_bug.cgi?id=8622
>
> Now apparently, there is a "LabeledStatement" in D:
> http://dlang.org/statement.html#LabeledStatement
>
> "Any statement can be labeled, including empty statements, and so can
> serve as the target of a goto statement. Labeled statements can also
> serve as the target of a break or continue statement."
>
> Never mind that you *can't* break out of a LabeledStatement (*only*
> labeled if/for/while), what I find spectacularly confusing is that this:
> LabeledStatement:
>    Identifier : NoScopeStatement
>
> "NoScopeStatement" means (apparently):
>
> //---- Legal Code
> int main()
> {
>    label:
>    {
>      int a = 4;
>    }
>    a = 4;
> }
> //----
> //---- Illegal Code
> int main()
> {
>    label1:
>    {
>      int a = 4;
>    }
>    label2:
>    {
>      int a = 4;
>    }
> }
> //----
> This behavior is because (apparently) a label followed by a "{}" does
> not create a new scope (!). Is this really what "NoScopeStatement" even
> means? I'd figure what I just wrote is a BlockStatement that's nested
> inside a NoScopeStatement...
>
> I'm trying to wrap my head around: Is this valid and behaving according
> to spec?

I think so, judging from Walter's comments in the bug reports.

> In particular, if this is "according to spec", what is the rationale for
> having the spec that way anyways? How is this any better then what we
> have in C? I don't suppose we deviate just for the fun of deviating...?
>
> In particular, I know I write BlockStatements all over the place,
> *especially* when labels and gotos start getting involved (to avoid
> jumping past declarations) I think this "feature" is at best useless,
> and at worst dangerous.
>
> Anybody have any insight on why we even have this?

I for one can't work out why anyone working to the spec would want to 
put braces after a label, knowing that they have no effect. It's very 
unintuitive.

I think it is a bug-prone design, considering the bug report examples.