Consider the following example:
http://dpaste.dzfl.pl/a0595ddf
----
// 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()
{
const(int) i;
try
{
i = createTheVar(); // Clearly not allowed
}
catch(Exception e) // For demo purposes
{
// Exception handling code
}
return transform(i);
}
----
I need to be able to catch an exception that may have been thrown
during the initialization of `i`, but still have `i` be const. I
can't omit the variable because I *don't* want to accidentally
catch anything that transform() may have thrown.
Note that the simple type const(int) is an example. This is
actually in highly generic code and the type may have mutable
indirection.
Here's the real-world code:
https://github.com/JakobOvrum/LuaD/blob/master/luad/conversions/functions.d#L86
The particular problematic type I happened to encounter for
RetType is the const(CacheInfo)[5] return type of
core.cpuid.dataCaches:
http://dlang.org/phobos/core_cpuid.html#.dataCaches
Specifics aside, I believe this is a very general problem.
----
Of course, if D had well-defined, local flow analysis like many
other modern languages (e.g. C#), this code would not have to be
rejected. I think that's a discussion for the future though;
right now it would be nice to have a workable, general
solution/workaround to the issue of initializing const/immutable
variables in try-blocks.
Any help is much appreciated.
