On Wednesday, 29 May 2013 at 15:11:53 UTC, Andrei Alexandrescu
wrote:
I must have missed part of this - how would the desired setup
work?
Andrei
Maybe something like the following would work. collectException's
return value and out parameter have been swapped for
demonstration - an out parameter for the result just moves the
problem to the body of collectException:
----
// Can throw, and we want to catch
int createTheVar();
// Can also throw, but we don't want to catch it here
int transform(int a);
int foo()
{
Exception e;
const(int) i = collectException(createTheVar(), e);
if(e)
// Exception handling code
return transform(i);
}
----
By removing the scope created by try-catch, the variable can be
declared and initialized at the same time, satisfying the
requirements of const/immutable. Further, the transform() call is
left unguarded as specified.
Such a collectionException works because it can use `return`
inside the try scope without broadening what it catches:
----
E collectException(T = Exception, E)(lazy E exp, out T ex)
{
try
return exp();
catch(T e)
{
ex = e;
return E.init; // Kind of a drawback
}
}
----
So, I guess using another function to do the try-catch is a
workable solution.
