Nested functions should be exempt from sequential visibility rules

[Timon Gehr]

On 04/03/2012 02:08 PM, Don Clugston wrote:
> On 03/04/12 13:58, Timon Gehr wrote:
>> On 04/03/2012 01:55 PM, Don Clugston wrote:
>>> On 03/04/12 13:35, Timon Gehr wrote:
>>>> On 04/03/2012 01:08 PM, Don Clugston wrote:
>>>>>
>>>>> Y b() { ... }
>>>>> Y y = b();
>>>>> X x = ...
>>>>>
>>>>> Prove that y doesn't depend on x.
>>>>
>>>> Since only function declarations are immune to ordering rules, b cannot
>>>> forward reference x.
>>>
>>> But there could be another function a() which is below x, and which b()
>>> calls.
>>
>> This scenario can be forbidden conservatively.
>
> How?

Don't allow forward referencing function a() if there is an intervening 
order-dependent declaration.

(Alternatively, just analyse which symbols are referenced where and 
don't allow calling a local function that can transitively reach some 
symbols that have not yet been declared. I think this might be too 
complicated to be justifiable.)