Is all this Invarient **** er... stuff, premature optimisation?

[Walter Bright]

Lionello Lunesu wrote:
> 
> "Walter Bright" <newshound1 at digitalmars.com> wrote in message 
> news:48169E90.6050700 at digitalmars.com...
>> Me Here wrote:
>>> Janice Caron wrote:
>>>> Functions don't overload on return value.
>>> They don't? Why not? Seems like a pretty obvious step to me.
>>
>> Type inference in D is done "bottom up". Doing overloading based on 
>> function return type is "top down". Trying to get both schemes to 
>> coexist is a hard problem.
> 
> But a function's result can be overloaded using "out", so why can't it 
> be overloaded using the return value?

We know what the type of the out argument is. The problem with return 
value overloading is not knowing what the type should be.


> Can't the compiler treat a return value as an implicit out argument?

Suppose the return value is used as an argument to another function with 
overloaded versions. Rinse, repeat. The combinations grow out of control.