Proposal: .isizeof property for compile-time instance size

[Sean Kelly]

S. Chancellor wrote:
> On 2006-04-09 13:28:41 -0700, Sean Kelly <sean at f4.ca> said:
> 
>> (this was originally posted to D bugs, but turned out to be a mistake 
>> so I'm reposting it here for discussion)
>>
>> As D lacks a lexical specifier for class reference types there is 
>> currently no way to determine the size of a class instance at 
>> compile-time.  A simple solution would be to add a new property, valid 
>> for pointer and reference types, that evaluates to the size of the 
>> referenced type.  Thus:
>>
>> (byte*).isizeof == byte.sizeof == 1
>> (byte**).isizeof == (byte*).sizeof == 4 (on 32-bit systems)
>> byte.isizeof == Error: property isizeof is only valid for reference 
>> types.
>>
>> MyClass { int x, y; }
>> MyClass.isizeof == 8
>> (MyClass*).isizeof == MyClass.sizeof == 4 (on 32-bit systems)
>>
>> Multiple levels of indirection can be eliminated using recursive 
>> templates, so there is no reason to collapse multiple levels of 
>> indirection and return the size of the final referenced type.
> 
> I'd rather see my proposal implemented, and then classes be in terms of 
> true references and then ad a "psizeof" to get the size of the physical 
> pointer or stack variable.  Of course, I would be bias toward my 
> proposal. :)

As long as there's some way to get the size of classes at compile time 
I'll be happy :-)


Sean