scope() and FileConduit (D1 and Tango)

[Jarrett Billingsley]

On Fri, Oct 3, 2008 at 8:58 PM, Bill Baxter <wbaxter at gmail.com> wrote:
> On Sat, Oct 4, 2008 at 7:08 AM, Jarrett Billingsley
> <jarrett.billingsley at gmail.com> wrote:
>> On Fri, Oct 3, 2008 at 4:57 PM, Nick Sabalausky <a at a.a> wrote:
>>> I'd like some clarification on the way scope() works, and also Tango's
>>> FileConduit. In the following function:
>>>
>>> void load(char[] infilename)
>>> {
>>>    auto file = new FileConduit(infilename);
>>>    scope(exit) file.close();
>>>
>>>    // Load data
>>> }
>>>
>>> What happens if infilename doesn't exist? Does FileConduit's constructor
>>> throw an exception? If so, file.close() isn't called, is it?
>>
>> Yes, the ctor throws an exception.  No, file.close is never called.
>> scope statements are only executed if execution reaches them
>> successfully.
>
> Oh, ok I see what the issue is now.  I think this will do the right thing:
>
> void load(char[] infilename)
> {
>   FileConduit file;
>   scope(exit) { if (file) file.close(); }
>   file = new FileConduit(infilename);
>    // Load data
> }

That's pretty much unnecessary, since in this code:

auto file = new FileConduit(infilename);
scope(exit) file.close();

if FileConduit's constructor fails, there is no file to close, so
there's no need to check for that.