[Ur] typechecker rejects form handler

[Sergey]

On 08.01.2014 00:07, Adam Chlipala wrote:
> On 01/07/2014 03:03 PM, Sergey wrote:
>> Well, for some reason I didn't take into account that 'show' instance 
>> is defined for the url type. I agree, this approach should work for 
>> now. But this way we handle basic cases only. For example, if I add 
>> one  trivial requirement to my login forms task - "views should print 
>> errors in case of invalid login attempt"  - then `form' function will 
>> need (string -> url) function argument rather than constant url and, 
>> thus, specializations. I can't see stable solution, that is why I'm 
>> so nervous about this problem.
>
> Your extra requirement turns out to be easy to support using cookies, 
> but I'm sure we could continue the escalation and find others that are 
> harder. :)
>
> For now, I don't see an "obvious good idea" change to make in Ur/Web, 
> so I'll wait until someone's actually current application forces a 
> different tack.
Of cause, cookies may help, but I feel disappointed because I can't rely 
on functional methods here. I don't fully understand why did you 
establish such a strict rules of mapping functions to urls, but I think 
I better understand the rules themselves. Hope you are right and the 
problem is not that serious in practice.

Regards,
Sergey