auto -> auto & var

[james]

In article <op.s6lxyol46b8z09 at ginger.vic.bigpond.net.au>, Derek Parnell says...
>
>On Mon, 13 Mar 2006 23:03:47 +1100, Lionello Lunesu  
><lio at remove.lunesu.com> wrote:
>
>>
>> "Kramer" <Kramer_member at pathlink.com> wrote in message
>> news:duspas$2dfo$1 at digitaldaemon.com...
>>> I keep tripping myself over the double meaning of auto.  I know it
>>> shouldn't be
>>> that difficult to remember that auto means type inference and also stack
>>> allocation/RAII, but does it have to be that way?
>>
>> Walter explained it: it does not have two meanings. The "auto" merely
>> notifies the compiler (or lexer, I don't know) that it's a declaration  
>> and a
>> variable name will follow.
>>
>> When the compiler encounters "auto x" it knows "x" is a variable. Since
>> "auto x" doesn't mention a type, it'll be derived.. Same thing for  
>> "static
>> x", x must be a variable, but there's no type so it'll be derived.
>
>This seems to be true, however the RAII behaviour is not invoked when this  
>syntax is used. So how does one declare an auto-type-infered and an  
>auto-RAII variable? For some example code ...
>
>import std.stdio;
>class bar
>{
>     this() { writefln("ctor bar"); }
>     ~this(){ writefln("dtor bar"); }
>}
>
>int foo()
>{
>     auto bar a = new bar;
>     return a.sizeof;
>}
>
>int xyz()
>{
>     auto a = new bar;
>     return a.sizeof;
>}
>
>void main()
>{
>     writefln("foo: %s", foo());
>     writefln("xyz: %s", xyz());
>}
>
>
>===========
>output:
>
>ctor bar
>dtor bar
>foo: 4
>ctor bar
>xyz: 4
>dtor bar
>===========
>
>Which seems to be showing that 'auto bar a = new bar;' is needed for RAII  
>behaviour and just 'auto a = new bar;' does type inference but no RAII.  
>And if one uses 'auto auto a = new bar' we get the compiler error  
>"redundant storage class 'auto'".
>
>-- 
>Derek Parnell
>Melbourne, Australia


Great example.

So with auto you can have either type inference OR raii for a particular
declaration. Why not both?
Does anyone know if this is the intended behaviour? And what is Walters thinking
on this?