[Lazarus] 'with' is evil, isn't it?

[Max Vlasov]

On Wed, Aug 3, 2011 at 3:34 PM, Michael Van Canneyt
<michael at freepascal.org>wrote:

>
> On Wed, 3 Aug 2011, Alexander Klenin wrote:
>
>  I also use 'with' extensively, despite the risks,
>> since with the right usage the readablity gains are considerable.
>>
>> 2011/8/3 Max Vlasov <max.vlasov at gmail.com>:
>>
>>> 1. Introducing a check in the compiler setting (or a conditional define)
>>> that could force the developer to use self inside 'with' constructions.
>>>
>> ...
>>
>>> 2. Some switch (maybe on by default) that prevents from compiling if
>>> there
>>> are several duplicate names in the same 'with' context (including global,
>>> local, fields).
>>>
>>
>> Error is IMHO too severe. I think a warning if the name inside of
>> 'with' overrides a name from outer scope
>> would be an acceptable compromise.
>>
>> Of course, a disambiguation facility would be even better,
>> but I am afraid FPC developers will resist this improvement :(
>>
>
> Frankly, I don't understand the discussion.
> I use 'with' all the time because it increases readability and reduces
> typing.
> I don't want to be punished with heaps of warnings simply because I use a
> language feature. Yes, I am aware that there are risks involved.
>
> If you don't like 'with', then don't use it, end of story.
>
> Introducing the proposed switch is nonsense, since it is useful only when
> dealing with other people's code. For your own code, you don't need this
> switch. Simply don't use 'with', and you're safe. If you type 'with' anyway,
> that would be very inconsequent of you.
>
>
Michael, one example from Sql
if you write something like

SELECT * FROM Detail LEFT JOIN Master on Detail.masterid=master.id where
id=34

sqlite and mysql, probably other dbms will stop you with 'ambiguous column
name' error,
The developers of these dbms could end up with some default way of context
resolving (for example the last mentioned table in the sentence), but they
did not. So many developers feel safer about the fact that if their detail
table will get some field with the same name as one of master's, the dbms
won't silently choose some field. I suppose this requirement could be even
the part of SQL-92. Talking about standards, I also admit that Wirth
probably never mentioned anything about the disambiguation resolving. But we
also can be sure that there was no objects and classes when he worked with
pascal so there were not much of a hidden context in the pascal sources.

By the way, there's the objfpc mode and it doesn't allow parameters have the
same names as field names. This is different to Delphi and generally
speaking I think this requirement lays in the same area as 'with'
disambiguation if implemented. Both serve more or less the same goal, don't
they?

Max
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