[erlang-bugs] Parser bug: if missing ", " in list between records, the first is ignored, and no parser warnings are given.

[Loïc Hoguin]

There are already warnings on otherwise correct syntax. Syntax being 
correct is why they are warnings and not errors. +warn_export_vars and 
+warn_shadow_vars are the most obvious examples.

I also want to note in addition to everything I mentioned that if such a 
warning is introduced, it needs to apply to both records and maps, as 
they both suffer from the same syntactic fragility.

On 11/09/2014 03:02 PM, Roland Karlsson wrote:
> Hi Mattias and Loïc.
>
> That #rec{}#rec{} is correct syntax is a result of how operators work.
> Making it not correct syntax needs a special treatment of this case.
> Which should be weird. Even more weird if it would be correct syntax in
> "advanced macros" only.
>
> Having a warning is another issue, warnings are based on heuristics
> and opinions.
>
>   Loïc - have you seen a warning if you e.g. write A*B+C  ?
> This expression (in principle) takes A*B, creating an unnamed
> variable. This unnamed variable is then added with C. Have you
> seen any warnings that this unnamed variable is unused?
> The same goes for #rec{}#rec{}. The first #rec{} creates an
> unnamed record of type rec. The second #rec{} modifies
> the unnamed record. You might not like the record syntax, and find
> the #rec{}#rec{} unreadable - but it is very clear what it does.
> BTW - the bit syntax and list comprehensions are even more hairy.
>
> Now, I am not a part of the OTP group or developing Erlang syntax, so
> it feels a bit awkward to defend it and be forced to come with
> motivations and proofs for being right.
>
> So - this is my last post on this subject.
>
>
> /Roland
>
>
>
>
> On Sun, 9 Nov 2014 13:23:59 +0100
> Mattias Waldau <mattias.waldau@REDACTED> wrote:
>
>> Hi All,
>>
>> I think the discussion went overboard. I made a small typo, forgetting a single comma in a static list.
>>
>> I know realize that
>>
>> #rec{}#rec{}
>>
>> is correct syntax, and I do not understand why it should be.
>>
>> Why not just say that it isn't ok? Who needs this syntax, except a advanced macro?
>>
>> /mattias
>

-- 
Loïc Hoguin
http://ninenines.eu