• Casey (10/10) Nov 08 2014 Good evening,
• Daniel Murphy (9/17) Nov 08 2014 import std.exception;
• Jonathan M Davis via Digitalmars-d (30/40) Nov 08 2014 Are you looking at the documentation or attempting to compile code?
• Casey (6/49) Nov 09 2014 First, sorry about that. I must have glossed over the d.learn

"Casey" <sybrandy gmail.com> writes:

Good evening,

I have a question for you.  Why does collectException violate the 
noThrow attribute?  I would have thought that since it captures 
an Exception, it would allow the method that normally would throw 
an exception to be used within a noThrow method.  I did get the 
same effect by nesting it within a assumeNoThrow method, but I'm 
still curious as to why collectException doesn't make the same 
guarantee.

Btw: this is with dmd 2.066.1.

Thanks.

"Daniel Murphy" <yebbliesnospam gmail.com> writes:

"Casey"  wrote in message news:kymxuhfmugteozqlfgmo forum.dlang.org...

 Good evening,

 I have a question for you.  Why does collectException violate the noThrow 
 attribute?  I would have thought that since it captures an Exception, it 
 would allow the method that normally would throw an exception to be used 
 within a noThrow method.  I did get the same effect by nesting it within a 
 assumeNoThrow method, but I'm still curious as to why collectException 
 doesn't make the same guarantee.

 Btw: this is with dmd 2.066.1.

import std.exception;

void main() nothrow
{
    collectException({ throw new Exception(null); });
}

Works fine to me.  Are you catching 'Exception' or catching a specific 
Exception subtype?  If the latter, there's your answer - other types of 
exceptions will still leak through. 

Jonathan M Davis via Digitalmars-d <digitalmars-d puremagic.com> writes:

On Sunday, November 09, 2014 03:15:21 Casey via Digitalmars-d wrote:
 Good evening,

 I have a question for you.  Why does collectException violate the
 noThrow attribute?  I would have thought that since it captures
 an Exception, it would allow the method that normally would throw
 an exception to be used within a noThrow method.  I did get the
 same effect by nesting it within a assumeNoThrow method, but I'm
 still curious as to why collectException doesn't make the same
 guarantee.

 Btw: this is with dmd 2.066.1.

 Thanks.

Are you looking at the documentation or attempting to compile code?
collectException isn't going to be marked as nothrow, because it can only be
nothrow if it's collectException!Exception (which _is_ the default), because
it can only be nothrow if no Exceptions (be they Exception or derived from
Exception) can escape the function - e.g. collectException!MyException can't
be nothrow - and neither can stuff like collectException!Error or
collectException!AssertError. collectException _should_ be inferred as
nothrow so long as it's collectException!Exception (and
collectException!Throwable should work as well, though I don't know if it
currently does).

If I compile this code on my machine using 2.066.1:

    import std.exception;
    import std.stdio;

    void func()
    {
        throw new Exception("hello");
    }

    void main() nothrow
    {
        auto e = collectException(func());
    }

it compiles just fine. So, it seems like nothrow is being properly inferred
for collectException, and I don't know what you're doing that isn't working.
Please provide a code snippet that you think should work but doesn't.

- Jonathan M Davis


P.S. In the future, please post questions like this is D.learn. The main
newsgroup/mailing list/forum is for discussing the language itself, not for
asking questions about how to use it or how it works (or doesn't work).

- Jonathan M Davis

"Casey" <sybrandy gmail.com> writes:

 Are you looking at the documentation or attempting to compile 
 code?
 collectException isn't going to be marked as nothrow, because 
 it can only be
 nothrow if it's collectException!Exception (which _is_ the 
 default), because
 it can only be nothrow if no Exceptions (be they Exception or 
 derived from
 Exception) can escape the function - e.g. 
 collectException!MyException can't
 be nothrow - and neither can stuff like collectException!Error 
 or
 collectException!AssertError. collectException _should_ be 
 inferred as
 nothrow so long as it's collectException!Exception (and
 collectException!Throwable should work as well, though I don't 
 know if it
 currently does).

 If I compile this code on my machine using 2.066.1:

     import std.exception;
     import std.stdio;

     void func()
     {
         throw new Exception("hello");
     }

     void main() nothrow
     {
         auto e = collectException(func());
     }

 it compiles just fine. So, it seems like nothrow is being 
 properly inferred
 for collectException, and I don't know what you're doing that 
 isn't working.
 Please provide a code snippet that you think should work but 
 doesn't.

 - Jonathan M Davis


 P.S. In the future, please post questions like this is D.learn. 
 The main
 newsgroup/mailing list/forum is for discussing the language 
 itself, not for
 asking questions about how to use it or how it works (or 
 doesn't work).

 - Jonathan M Davis

First, sorry about that.  I must have glossed over the d.learn 
forum.

Second, I actually did compile and run it and got the failure.  
However, reading your response, I'm not wondering if I did make a 
mistake.  In fact, I just tried it again and it did work.  
Regardless, what you said makes sense.  Thanks.